- U.S. National Center for Environmental Prediction (NCEP)
Showing posts with label Weather Forecasting. Show all posts
Showing posts with label Weather Forecasting. Show all posts
Saturday, 30 March 2013
GFS Medium Range Forecasts of Vertical Velocity and Precipitation: South Africa
- U.S. National Center for Environmental Prediction (NCEP)
Wednesday, 13 February 2013
Counting raindrops
How to use mobile-phone networks for weather forecasting.
FORECASTING the weather requires huge quantities of data. Many of these data are collected by high-tech means such as satellites and radar, and then crunched by some of the world’s fastest supercomputers into predictions that are far more accurate than they were 20 years ago. But low-tech tools are important too—especially old-fashioned rain gauges, which are nothing more than tubes with funnels fixed to places such as rooftops.
Each technique has its upsides and downsides. Radar and satellites can cover swathes of land, yet they lack detail. Gauges are much more accurate, but the price of that accuracy is spotty coverage. Now, though, Aart Overeem of the Royal Netherlands Meteorological Institute and his colleagues reckon they have come up with another way to keep an eye on the rain. It offers, they believe, both broad coverage and fine detail. Best of all, it relies on something that is already almost omnipresent—the mobile-phone network.
Their scheme starts from the observation that rain can make it harder for certain sorts of electromagnetic radiation to travel through the atmosphere. Measure this impedance (and scrub out any other sources of variation) and you can measure how rainy it is. The researchers do not measure the strength of mobile-phone signals themselves. Instead, they piggyback on something that mobile networks already do, and measure the strength of the microwave links that base stations use to talk to each other.
The idea itself is not new, and there have been trials in recent years. But, as they report in the Proceedings of the National Academy of Sciences, Dr Overeem and his colleagues have successfully applied the technique to an entire country. Using data from around 2,400 links between base-stations belonging to T-Mobile, one of the Netherlands’ three mobile-phone operators, they were able to generate a rain map of the whole kingdom every 15 minutes.
Like all the best science, the idea is both technically elegant and practically useful. Dr Overeem points out that simply coming up with another way to measure rainfall is handy by itself, since it allows better cross-checking of existing methods. There are other advantages, too. Coverage is one. Even in rich countries with well-financed weather forecasters, there are likely to be far more mobile-phone base stations than rain gauges. That is truer still in poor countries, where rain gauges are scarce and radar often nonexistent, but mobile phones common. The GSM Association, a mobile-phone trade group, estimates that 90% of the world’s population lives within range of a base station.
Another boon is that network operators tend to keep a close eye on their microwave links. Although the researchers were able to obtain data only every 15 minutes, some firms sample their networks once a minute. That means rainfall could, in principle, be measured almost in real time, something that neither gauges nor radar nor satellites can manage.
The technology is not perfect: snow and hail are harder than rain for microwaves to spot, for example. And there are other caveats. Mobile networks are densest in urban areas, which are also the places most likely to have meteorological equipment already. Even in the rich, urbanised Netherlands, coverage outside cities was noticeably patchier. But that might eventually prove to be a boon, for if the technology becomes widespread then weather forecasters might contribute to the cost of installing base stations in coverage blackspots—something for which the 10% of humanity not yet within range of a mobile-phone mast might be thankful.
- The Economist
FORECASTING the weather requires huge quantities of data. Many of these data are collected by high-tech means such as satellites and radar, and then crunched by some of the world’s fastest supercomputers into predictions that are far more accurate than they were 20 years ago. But low-tech tools are important too—especially old-fashioned rain gauges, which are nothing more than tubes with funnels fixed to places such as rooftops.
Each technique has its upsides and downsides. Radar and satellites can cover swathes of land, yet they lack detail. Gauges are much more accurate, but the price of that accuracy is spotty coverage. Now, though, Aart Overeem of the Royal Netherlands Meteorological Institute and his colleagues reckon they have come up with another way to keep an eye on the rain. It offers, they believe, both broad coverage and fine detail. Best of all, it relies on something that is already almost omnipresent—the mobile-phone network.
Their scheme starts from the observation that rain can make it harder for certain sorts of electromagnetic radiation to travel through the atmosphere. Measure this impedance (and scrub out any other sources of variation) and you can measure how rainy it is. The researchers do not measure the strength of mobile-phone signals themselves. Instead, they piggyback on something that mobile networks already do, and measure the strength of the microwave links that base stations use to talk to each other.
The idea itself is not new, and there have been trials in recent years. But, as they report in the Proceedings of the National Academy of Sciences, Dr Overeem and his colleagues have successfully applied the technique to an entire country. Using data from around 2,400 links between base-stations belonging to T-Mobile, one of the Netherlands’ three mobile-phone operators, they were able to generate a rain map of the whole kingdom every 15 minutes.
Like all the best science, the idea is both technically elegant and practically useful. Dr Overeem points out that simply coming up with another way to measure rainfall is handy by itself, since it allows better cross-checking of existing methods. There are other advantages, too. Coverage is one. Even in rich countries with well-financed weather forecasters, there are likely to be far more mobile-phone base stations than rain gauges. That is truer still in poor countries, where rain gauges are scarce and radar often nonexistent, but mobile phones common. The GSM Association, a mobile-phone trade group, estimates that 90% of the world’s population lives within range of a base station.
Another boon is that network operators tend to keep a close eye on their microwave links. Although the researchers were able to obtain data only every 15 minutes, some firms sample their networks once a minute. That means rainfall could, in principle, be measured almost in real time, something that neither gauges nor radar nor satellites can manage.
The technology is not perfect: snow and hail are harder than rain for microwaves to spot, for example. And there are other caveats. Mobile networks are densest in urban areas, which are also the places most likely to have meteorological equipment already. Even in the rich, urbanised Netherlands, coverage outside cities was noticeably patchier. But that might eventually prove to be a boon, for if the technology becomes widespread then weather forecasters might contribute to the cost of installing base stations in coverage blackspots—something for which the 10% of humanity not yet within range of a mobile-phone mast might be thankful.
- The Economist
Friday, 1 February 2013
GFS Medium Range Forecasts of Vertical Velocity and Precipitation: South Africa
- U.S. National Center for Environmental Prediction (NCEP)
Saturday, 19 January 2013
Forecast: 3 day total precipitation: South Africa
Image: NOAA Climate Prediction Center (Click on image for larger view.)
Friday, 18 January 2013
GFS Medium Range Forecasts of Vertical Velocity and Precipitation: South Africa
- U.S. National Center for Environmental Prediction (NCEP)
Friday, 4 January 2013
GFS Medium Range Forecasts of Vertical Velocity and Precipitation: South Africa
- U.S. National Center for Environmental Prediction (NCEP)
Wednesday, 2 January 2013
GFS 72 Hour Forecasts of Vertical Velocity and Precipitation: South Africa
- U.S. National Center for Environmental Prediction (NCEP)
Tuesday, 1 January 2013
GFS 72 Hour Forecasts of Vertical Velocity and Precipitation: South Africa
- U.S. National Center for Environmental Prediction (NCEP)
Monday, 31 December 2012
South Africa New Years Eve Weather Forecast by Derek Van Dam
South Africa's New Years Eve weather forecast! Have a great New Year Everyone! - Derek Van Dam
Wednesday, 26 December 2012
GFS 72 Hour Forecasts of Vertical Velocity and Precipitation: South Africa
Images: U.S. National Center for Environmental Prediction (NCEP) Click on images for larger view.
Tuesday, 11 December 2012
GFS 72 Hour Forecasts of Vertical Velocity and Precipitation: South Africa
Images: U.S. National Center for Environmental Prediction (NCEP) (Click on images for larger view.)
Sunday, 4 November 2012
The good, the bad, and the ugly … learning from Hurricane Sandy
Looking back at the entire track of Superstorm/Frankenstorm/Non-Tropical Cyclone/Extratropical Cyclone Sandy (yes, the storm has had a bunch of names!), it is really amazing to see how it formed and how the science got this storm right.
It also gave me a horrible feeling about what could come out of this storm, as I knew so many deadly scenarios were in play. I have decided to highlight the good, the bad, and ugly parts about Hurricane Sandy. While most of this was simply ugly, there were a few good things that came out of this forecast. Let’s take a look back at Hurricane Sandy and see what went right and what went wrong.
The Good:
One word: Science
The forecast for Sandy was fantastic, and could be considered as one of the finest moments in meteorology. The European Centre for Medium-Range Weather Forecasts, also known as ECMWF or the European model, nailed down the track of Sandy a week before the storm pushed into southern New Jersey. The Europeans have more money invested into their weather model, and it uses 4D data assimilation unlike our American model, the Global Forecast System (GFS).
Seven days before the event, the GFS model insisted that Sandy would push out to sea and possibly affect Bermuda. However, run after run of consistent forecasts, the European model kept its solution of a New England storm affecting millions of people.
With such a huge concern about Sandy, NOAA decided that the local national weather services should launch special radiosondes (weather balloons) every six hours to get a better measure of what was happening within our atmosphere. These measurements about barometric pressure, temperature, wind speeds with height, and so much more was able to help the models create better runs so meteorologists would have a better idea of the track of the storm. If one feature pushed out or formed differently, it could easily change the track of Sandy. Using weather satellites such as GOES-13, which monitors the Eastern Seaboard and Atlantic ocean, can also help us not only get visible images of Earth from outer space, but it also grabs a lot of data and information that we also use in our weather models. If you can recall, GOES-13 experienced a lot of noise and had to be replaced by a temporary satellite until it was fixed a few months ago.
I wrote a post about how we may begin to see a rapid decline in U.S. satellites in the near future. According to a report from the National Research Council in early 2012, U.S. satellites in orbit are expected to decline from 23 in 2012 to only six in the year of 2020. Long-running missions to build and launch satellites are undergoing delays, missions are being cut as budgets are cut, and there have been some inevitable launch failures, plus changes in mission design and scope. If we do not improve these problems, then all of the progress we have made in the study of atmospheric sciences will be for nothing. Now, do you see how important it is to fund and receive full support for NOAA/NASA? If we never had satellites or weather models, then what happened on Monday evening, October 29, 2012 could have been another repeat of the 1938 Long Island hurricane that swept New York by surprise and killed hundreds of people. Fortunately, science prevailed and gave us plenty of time to warn the general public about the danger of Hurricane Sandy.
The Bad:
-Confusion
I will state this first: I know there are plenty of people that took this storm seriously. If people were told to evacuate their homes, then many people did. However, there was confusion regarding the storm and its impact. For instance, do you remember Hurricane Irene from last year? Although the storm caused significant flooding and damage across New England, it was no where near the sense of dangerous as originally hyped. For some people, Irene was not a big deal. This “false” sense of being safe can really get people in trouble, and I find that to be a huge issue. You will find a few meteorologists who “hype” storms every now and then simply for ratings. When it comes to listening to people for weather information, it call comes down to who you trust and listen to. When meteorologists and local NWS decide to use strong wording in their forecasts and discussions to give the public a sense of urgency and that danger is near, you should always listen. When I wrote up a post about Sandy, I decided to title it “Hurricane Sandy is dangerous” to give everyone a sense that this storm means business.
One huge area of concern I had was the process of not issuing hurricane watches or warnings along the New Jersey and New York coasts. The original idea from the National Hurricane Center was that this storm would become extratropical and thus not be a hurricane as it pushed inland. I understand the science of how it works regarding the transition of a warm core low becoming a cold core. However, the general public does not understand. Instead of issuing hurricane warnings, the NHC gave the local NWS offices to issue their own warnings. Some of the warnings such as “High wind warnings” were not only issued along the coasts where Sandy was suppose to make landfall, but these warnings were also issued as far south as North Georgia. My issue: Does the general public understand the definition of a high wind warning? I will admit, I had to double check the definition myself to understand what it truly means.
High Wind Warning definition:
A warning for sustained surface winds greater than 40 mph/64 kph lasting more than an hour or winds over 58 mph/93 kph over land that are either predicted or occurring for an unspecified period of time.
For some people, this definition simply tells them that it will be very windy outside. However, does it really strike concern for most people? Personally, I believe the National Hurricane Center should have issued hurricane warnings. Many meteorologists via social media questioned their actions, and I am sure this will still be a topic that will be mentioned in future discussions about the warning process of Hurricane Sandy. This topic got so out of hand, the National Hurricane Center actually released a PDF online explaining their actions of not issuing hurricane warnings.
-Social Media
If you follow social media, you probably had information overload regarding Hurricane Sandy. At one point, there were confirmations that the New York Stock Exchange was flooding. Twenty minutes later, we had a new confirmation that this was not the case. In fact, the biggest thing that bothers me is when people post fake images. Every time a major storm hits part of the United States, people tend to grab the same images over and over and claim it was from that particular event. I saw it during Hurricane Katrina, and I also saw it during the April 14-15, 2012 tornado outbreak across the Central Plains. Here’s my favorite example of the fake picture that circulated online:
I will admit though, the image below is a little more believable. No?
Either way, putting out fake images adds confusion for broadcast meteorologists/journalists who are trying to showcase what is actually happening during an event. If you are out there and think it is funny to photoshop old storms and claim it was something else, it isn’t. I cannot tell you how many times I have seen fake hail images, supercell structures that occurred a decade ago, and more. It is important to know who you follow when it comes to getting information. Is the source reliable? If so, you should still double check the picture. Sometimes, the photos are so good, that even reliable sources get fooled. I will admit, it has happened to me.
The Ugly
As of now, at least 81 people in the U.S. have died from Sandy. Many of the deaths occurred from trees falling on cars and buildings. Sandy is also responsible for 67 deaths in the Caribbean, and two deaths in Canada. Overall, at least 150 people have passed away from this brutal storm. The damage has been extensive and beyond comprehensible, especially along the Jersey shore. There is no doubt Sandy reshaped the coastline as storm surge brought piles of sand well inland and destroyed homes and bridges along the coast. Many houses were simply pushed off its foundation and shifted to a different location. Cars were buried in water, and the subway stations flooded. There is no doubt in my mind that Hurricane Sandy will rank as one of the top three costliest weather disasters in United States history. Prayers go out to all of the victims that are fighting through this horrible tragedy.
Bottom line: The forecasts for Sandy were excellent, and the ECMWF weather model saw this storm developing and pushing into the Mid-Atlantic/New England about eight days before actual landfall. I believe there could have been confusion regarding the lack of hurricane watches and warnings that were not issued for portions New Jersey and New York. As the storm hit, social media was excellent on getting real time information as it came in. However, there were a lot of fake images that were being shared around. I wish this never happened, but it tends to be the case whenever a significant weather event occurs. Finally, the ugly part of Sandy is the death and destruction that has occurred not only in the United States, but also in the Caribbean. The death count has surpassed over 150 deaths, which is one too many. Prayers go out to everyone affected by Hurricane Sandy.
- EarthSky
It also gave me a horrible feeling about what could come out of this storm, as I knew so many deadly scenarios were in play. I have decided to highlight the good, the bad, and ugly parts about Hurricane Sandy. While most of this was simply ugly, there were a few good things that came out of this forecast. Let’s take a look back at Hurricane Sandy and see what went right and what went wrong.
The Good:
One word: Science
The forecast for Sandy was fantastic, and could be considered as one of the finest moments in meteorology. The European Centre for Medium-Range Weather Forecasts, also known as ECMWF or the European model, nailed down the track of Sandy a week before the storm pushed into southern New Jersey. The Europeans have more money invested into their weather model, and it uses 4D data assimilation unlike our American model, the Global Forecast System (GFS).
Seven days before the event, the GFS model insisted that Sandy would push out to sea and possibly affect Bermuda. However, run after run of consistent forecasts, the European model kept its solution of a New England storm affecting millions of people.
With such a huge concern about Sandy, NOAA decided that the local national weather services should launch special radiosondes (weather balloons) every six hours to get a better measure of what was happening within our atmosphere. These measurements about barometric pressure, temperature, wind speeds with height, and so much more was able to help the models create better runs so meteorologists would have a better idea of the track of the storm. If one feature pushed out or formed differently, it could easily change the track of Sandy. Using weather satellites such as GOES-13, which monitors the Eastern Seaboard and Atlantic ocean, can also help us not only get visible images of Earth from outer space, but it also grabs a lot of data and information that we also use in our weather models. If you can recall, GOES-13 experienced a lot of noise and had to be replaced by a temporary satellite until it was fixed a few months ago.
The track for Sandy was great. The weather models and the NHC has a great forecast for the track of Hurricane Sandy. Image Credit: NOAA
I wrote a post about how we may begin to see a rapid decline in U.S. satellites in the near future. According to a report from the National Research Council in early 2012, U.S. satellites in orbit are expected to decline from 23 in 2012 to only six in the year of 2020. Long-running missions to build and launch satellites are undergoing delays, missions are being cut as budgets are cut, and there have been some inevitable launch failures, plus changes in mission design and scope. If we do not improve these problems, then all of the progress we have made in the study of atmospheric sciences will be for nothing. Now, do you see how important it is to fund and receive full support for NOAA/NASA? If we never had satellites or weather models, then what happened on Monday evening, October 29, 2012 could have been another repeat of the 1938 Long Island hurricane that swept New York by surprise and killed hundreds of people. Fortunately, science prevailed and gave us plenty of time to warn the general public about the danger of Hurricane Sandy.
The Bad:
-Confusion
I will state this first: I know there are plenty of people that took this storm seriously. If people were told to evacuate their homes, then many people did. However, there was confusion regarding the storm and its impact. For instance, do you remember Hurricane Irene from last year? Although the storm caused significant flooding and damage across New England, it was no where near the sense of dangerous as originally hyped. For some people, Irene was not a big deal. This “false” sense of being safe can really get people in trouble, and I find that to be a huge issue. You will find a few meteorologists who “hype” storms every now and then simply for ratings. When it comes to listening to people for weather information, it call comes down to who you trust and listen to. When meteorologists and local NWS decide to use strong wording in their forecasts and discussions to give the public a sense of urgency and that danger is near, you should always listen. When I wrote up a post about Sandy, I decided to title it “Hurricane Sandy is dangerous” to give everyone a sense that this storm means business.
One huge area of concern I had was the process of not issuing hurricane watches or warnings along the New Jersey and New York coasts. The original idea from the National Hurricane Center was that this storm would become extratropical and thus not be a hurricane as it pushed inland. I understand the science of how it works regarding the transition of a warm core low becoming a cold core. However, the general public does not understand. Instead of issuing hurricane warnings, the NHC gave the local NWS offices to issue their own warnings. Some of the warnings such as “High wind warnings” were not only issued along the coasts where Sandy was suppose to make landfall, but these warnings were also issued as far south as North Georgia. My issue: Does the general public understand the definition of a high wind warning? I will admit, I had to double check the definition myself to understand what it truly means.
High Wind Warning definition:
A warning for sustained surface winds greater than 40 mph/64 kph lasting more than an hour or winds over 58 mph/93 kph over land that are either predicted or occurring for an unspecified period of time.
For some people, this definition simply tells them that it will be very windy outside. However, does it really strike concern for most people? Personally, I believe the National Hurricane Center should have issued hurricane warnings. Many meteorologists via social media questioned their actions, and I am sure this will still be a topic that will be mentioned in future discussions about the warning process of Hurricane Sandy. This topic got so out of hand, the National Hurricane Center actually released a PDF online explaining their actions of not issuing hurricane warnings.
-Social Media
If you follow social media, you probably had information overload regarding Hurricane Sandy. At one point, there were confirmations that the New York Stock Exchange was flooding. Twenty minutes later, we had a new confirmation that this was not the case. In fact, the biggest thing that bothers me is when people post fake images. Every time a major storm hits part of the United States, people tend to grab the same images over and over and claim it was from that particular event. I saw it during Hurricane Katrina, and I also saw it during the April 14-15, 2012 tornado outbreak across the Central Plains. Here’s my favorite example of the fake picture that circulated online:
Fake image that circulated through social media claiming Hurricane Sandy was producing a supercell over New York City. Really? Image Credit: Who cares
I will admit though, the image below is a little more believable. No?
In attack of the spread of fake images online, someone decided to add a little humor to the situation.
Either way, putting out fake images adds confusion for broadcast meteorologists/journalists who are trying to showcase what is actually happening during an event. If you are out there and think it is funny to photoshop old storms and claim it was something else, it isn’t. I cannot tell you how many times I have seen fake hail images, supercell structures that occurred a decade ago, and more. It is important to know who you follow when it comes to getting information. Is the source reliable? If so, you should still double check the picture. Sometimes, the photos are so good, that even reliable sources get fooled. I will admit, it has happened to me.
The Ugly
Tree damage in South Richmond Hill, New York. Image Credit: WABC TV Channel 7 Eyewitness News
As of now, at least 81 people in the U.S. have died from Sandy. Many of the deaths occurred from trees falling on cars and buildings. Sandy is also responsible for 67 deaths in the Caribbean, and two deaths in Canada. Overall, at least 150 people have passed away from this brutal storm. The damage has been extensive and beyond comprehensible, especially along the Jersey shore. There is no doubt Sandy reshaped the coastline as storm surge brought piles of sand well inland and destroyed homes and bridges along the coast. Many houses were simply pushed off its foundation and shifted to a different location. Cars were buried in water, and the subway stations flooded. There is no doubt in my mind that Hurricane Sandy will rank as one of the top three costliest weather disasters in United States history. Prayers go out to all of the victims that are fighting through this horrible tragedy.
Bottom line: The forecasts for Sandy were excellent, and the ECMWF weather model saw this storm developing and pushing into the Mid-Atlantic/New England about eight days before actual landfall. I believe there could have been confusion regarding the lack of hurricane watches and warnings that were not issued for portions New Jersey and New York. As the storm hit, social media was excellent on getting real time information as it came in. However, there were a lot of fake images that were being shared around. I wish this never happened, but it tends to be the case whenever a significant weather event occurs. Finally, the ugly part of Sandy is the death and destruction that has occurred not only in the United States, but also in the Caribbean. The death count has surpassed over 150 deaths, which is one too many. Prayers go out to everyone affected by Hurricane Sandy.
- EarthSky
Saturday, 30 June 2012
SAWS Storm Warning for Johannesburg - 30 June 2012 15h00
30 June 12 Norwood : SAWS Warning for Johannesburg. Very odd – no sign of cloud near or far?? Obs. B & L Cohen
SAWDOS - Any thunderstorms in the Johannesburg area this afternoon?
UPDATE: 1 July 2012 - Thanks to all those who confirmed that there was no thunderstorm activity yesterday afternoon. I just thought that my crystal ball is broken as I could not see any clouds over Gauteng yesterday afternoon. Like somebody commented: ..... only clouds over Johannesburg were clouds of smoke. For more comments go to the SAWDOS Facebook Group.
Friday, 8 June 2012
GFS Rain / Freezing Rain / Snow forecast for 9 June 2012
Cor of Secundaweather writes:
I will be posting a lot on the cold front reaching Gauteng/Mpumalanga.
I will use the blog page to post regular updates, which can be viewed
here: http://secundaweather.co.za/blog
Thursday, 10 May 2012
Prince Charles turns BBC Scotland weatherman
Prince Charles presents a special weather forecast during his BBC Scotland visit
Prince Charles had a go at reading the weather during a tour of BBC Scotland's Pacific Quay headquarters.
He and his wife, the Duchess of Cornwall, visited the broadcaster as a part of their annual Holyrood Week.
BBC newsreader Sally Magnusson handed over to Prince Charles, who read his version of Reporting Scotland's lunchtime weather.
The prince, also known as the Duke of Rothesay, had earlier met students at the City of Glasgow College.
Against a backdrop of the BBC's weather map, Prince Charles delivered a specially written script which included references to royal residences in Scotland.
Looking directly into the camera, he said: "The best of the bright and dry weather will of course be in the northern isles and the far north of the mainland. So, a little hazy sunshine for the Castle of Mey in Caithness.
"But a cold day everywhere with temperatures of just 8C and a brisk northerly wind. Thank God it isn't a bank holiday."
The duke and duchess spent more than an hour at BBC Scotland, which is celebrating 60 years of television broadcasting.
- BBC
Thursday, 1 March 2012
TROPICAL STORM IRINA ON THE WAY TO SOUTHERN MOZAMBIQUE AND PARTS OF SOUTH AFRICA DURING THIS WEEKEND
DATE: 01 MARCH 2012
FOR IMMEDIATE RELEASE
Current Situation
At 1400SAST this afternoon, Moderate Tropical Storm “IRINA” was located at 19.5 S / 043.7 E within the central part of the Mozambique Channel, just on the west coast of Madagascar, near the town of Maintirano. The eye of the system is somewhat obscured at the moment, but the distinctive spiral banding features, characteristic of such systems, are nevertheless well-defined. “IRINA” is currently moving southwards at 13 knots (24 km/h).
Earlier in its lifetime, the storm had its origins over the open ocean, eastwards of Madagascar. It moved mainly westwards, directly over the landmass of Madagascar, weakening the system significantly.
However, a number of environmental factors in the Mozambique Channel remain favourable for
sustainable development of tropical cyclones and consequently the system has re-organised and
progressively deepened (intensified) over the last few days.
Values of sea-surface temperature (SST) remain significantly elevated over the ocean region of the west coast of Madagascar, with observed values of SST of the order of 29˚C to 31˚C, thus providing the main source of energy, driving such tropical systems. Furthermore, the airflow in the uppermost regions of the storm is such that rising air (from the core of the storm) is rapidly carried away at high altitude. Such airflow is ‘divergent’ in nature and is a key feature of sustained development of the storm. Whilst there are numerous such “ingredients” that contribute positively towards tropical cyclone development, it is notable that there are currently no negative factors that could lead to the short-term weakening or decay of the system. On the contrary, it seems likely that within the following 48 hours, the system is
anticipated to intensify to attain full “Tropical Cyclone” status.
Figure 1. Location of Moderate tropical Storm “IRINA” in the Mozambique Channel, off the west coast of Madagascar at 12h00 SAST. © EUMETSAT 2012, METEOSAT 9, IR10.8um channel.
Expected Sequence of Events
Whilst the current track of “IRINA” is a predominantly southward one, it is predicted that the track will shift towards south-west at the beginning of the weekend. The ensemble output from ECMWF (Figure 2, below) is suggesting with a fairly high degree of sustained confidence, that once the south-westward movement is adopted, it will most likely result in the system maintaining this track, resulting in landfall close to Inhambane and Xai-Xai in the early morning hours of Monday 5th March (and ultimately the general area around Maputo later on Monday).
Furthermore, once the system is in the general area of Maputo, Mozambique, it seems most probable at this stage that the system will slow down and ‘stall’ for a period of about 48 hours. The reason for this is that an upper-air ridge over southern Africa is expected to form a buffer or obstacle, preventing the southward escape of the tropical system.
Impacts on Southern Africa
As can be seen from the sequence of predicted rainfall (figures 3 to 5 below), it is highly likely that an episode of widespread heavy to torrential rain can be expected over a large portion of southern Mozambique as well as eastern Limpopo province, eastern Mpumalanga, KwaZulu-Natal (especially in the north at first) as well as Swaziland.
Within the regions mentioned above, areas PARTICULARLY AT RISK would be the southern coast and adjacent interior of Mozambique, between Inhambane and Ponte do Ouro, extending down to include the Maputaland coast and adjacent interior of extreme north-eastern KwaZulu-Natal. Kosi Bay, St Lucia as well as Richards Bay are thus also considered to be well within the high risk region.
These areas can expect accumulated rainfall of the order of 300 to 400mm over 2 to 3 days. This is rainfall of an extreme and exceptional nature (last experienced in this region when tropical cyclone DOMOINA affected KwaZulu-Natal in 1984, when 400 to 600mm was recorded over a similar period). Marine storm surge (a local sea rise of sea level in close proximity to the core of the tropical storm) as well as gale-force winds are also likely along aforementioned coastline.
To a somewhat lesser extent, the adjacent regions of eastern Limpopo province, eastern Mpumalanga, the remainder of KwaZulu-Natal and Swaziland could easily experience 100 to 200mm of accumulated rain during the period Sunday to Tuesday. Water flow entering river systems and dams within this sub-region is quite likely to exceed the carrying capacity of the rivers across a widespread area. The danger of flash-flooding and localised washaways should also be kept in mind. The public are therefore urged to be extremely cautious and (if possible) to avoid crossing swollen rivers, either on foot or by vehicle.
An additional topographic feature of Mpumalanga and Limpopo is the Eastern Escarpment region, which (through orographic lifting of moisture-laden air) is likely to significantly enhance rainfall on the windward (eastern) side of the Escarpment. Rainfall along this geographic area is likely to be of the order of “more than 200mm” at places over a two to three day period.
Finally, with the escape of IRINA being blocked by an upper-air ridge (as alluded to above), the last weather-related mechanism we need to consider is the expected arrival of a surface ridging high, around the southern tip of the continent, introducing fresh southerly to south-easterly airflow along the eastern seaboard (including KwaZulu-Natal) of South Africa, between Monday and Tuesday (as per figures 4 and 5 below). This is likely to sustain and enhance the heavy rain conditions along the KwaZulu-Natal coastline and interior, thus exacerbating the effects of an already severe weather pattern.
The South African Weather Service further wishes to state that the public can rest assured that the situation will continue to be closely monitored 24/7 throughout the weekend and beyond.
Further updates regarding this weather system will be issued at regular intervals to keep the public informed.
What common-sense precautions should I take?
ENDS
Issued by:
South African Weather Service (SAWS)
SAWDOS: Congratulations to the SAWS for getting the severe weather message out well in advance of the approaching storm. The public should take note of the above media release and take the necessary precautions to protect themselves and their property if at all possible. It would appear that TS Irina could be worse the TS Dando. Time will tell whether this will be the case.
FOR IMMEDIATE RELEASE
Current Situation
At 1400SAST this afternoon, Moderate Tropical Storm “IRINA” was located at 19.5 S / 043.7 E within the central part of the Mozambique Channel, just on the west coast of Madagascar, near the town of Maintirano. The eye of the system is somewhat obscured at the moment, but the distinctive spiral banding features, characteristic of such systems, are nevertheless well-defined. “IRINA” is currently moving southwards at 13 knots (24 km/h).
Earlier in its lifetime, the storm had its origins over the open ocean, eastwards of Madagascar. It moved mainly westwards, directly over the landmass of Madagascar, weakening the system significantly.
However, a number of environmental factors in the Mozambique Channel remain favourable for
sustainable development of tropical cyclones and consequently the system has re-organised and
progressively deepened (intensified) over the last few days.
Values of sea-surface temperature (SST) remain significantly elevated over the ocean region of the west coast of Madagascar, with observed values of SST of the order of 29˚C to 31˚C, thus providing the main source of energy, driving such tropical systems. Furthermore, the airflow in the uppermost regions of the storm is such that rising air (from the core of the storm) is rapidly carried away at high altitude. Such airflow is ‘divergent’ in nature and is a key feature of sustained development of the storm. Whilst there are numerous such “ingredients” that contribute positively towards tropical cyclone development, it is notable that there are currently no negative factors that could lead to the short-term weakening or decay of the system. On the contrary, it seems likely that within the following 48 hours, the system is
anticipated to intensify to attain full “Tropical Cyclone” status.
Figure 1. Location of Moderate tropical Storm “IRINA” in the Mozambique Channel, off the west coast of Madagascar at 12h00 SAST. © EUMETSAT 2012, METEOSAT 9, IR10.8um channel.
Expected Sequence of Events
Whilst the current track of “IRINA” is a predominantly southward one, it is predicted that the track will shift towards south-west at the beginning of the weekend. The ensemble output from ECMWF (Figure 2, below) is suggesting with a fairly high degree of sustained confidence, that once the south-westward movement is adopted, it will most likely result in the system maintaining this track, resulting in landfall close to Inhambane and Xai-Xai in the early morning hours of Monday 5th March (and ultimately the general area around Maputo later on Monday).
Furthermore, once the system is in the general area of Maputo, Mozambique, it seems most probable at this stage that the system will slow down and ‘stall’ for a period of about 48 hours. The reason for this is that an upper-air ridge over southern Africa is expected to form a buffer or obstacle, preventing the southward escape of the tropical system.
Figure 2. ECMWF ensemble prediction of percentage confidence of the future track of IRINA, for the following 120hrs (5 days).
Impacts on Southern Africa
As can be seen from the sequence of predicted rainfall (figures 3 to 5 below), it is highly likely that an episode of widespread heavy to torrential rain can be expected over a large portion of southern Mozambique as well as eastern Limpopo province, eastern Mpumalanga, KwaZulu-Natal (especially in the north at first) as well as Swaziland.
Within the regions mentioned above, areas PARTICULARLY AT RISK would be the southern coast and adjacent interior of Mozambique, between Inhambane and Ponte do Ouro, extending down to include the Maputaland coast and adjacent interior of extreme north-eastern KwaZulu-Natal. Kosi Bay, St Lucia as well as Richards Bay are thus also considered to be well within the high risk region.
These areas can expect accumulated rainfall of the order of 300 to 400mm over 2 to 3 days. This is rainfall of an extreme and exceptional nature (last experienced in this region when tropical cyclone DOMOINA affected KwaZulu-Natal in 1984, when 400 to 600mm was recorded over a similar period). Marine storm surge (a local sea rise of sea level in close proximity to the core of the tropical storm) as well as gale-force winds are also likely along aforementioned coastline.
To a somewhat lesser extent, the adjacent regions of eastern Limpopo province, eastern Mpumalanga, the remainder of KwaZulu-Natal and Swaziland could easily experience 100 to 200mm of accumulated rain during the period Sunday to Tuesday. Water flow entering river systems and dams within this sub-region is quite likely to exceed the carrying capacity of the rivers across a widespread area. The danger of flash-flooding and localised washaways should also be kept in mind. The public are therefore urged to be extremely cautious and (if possible) to avoid crossing swollen rivers, either on foot or by vehicle.
An additional topographic feature of Mpumalanga and Limpopo is the Eastern Escarpment region, which (through orographic lifting of moisture-laden air) is likely to significantly enhance rainfall on the windward (eastern) side of the Escarpment. Rainfall along this geographic area is likely to be of the order of “more than 200mm” at places over a two to three day period.
Finally, with the escape of IRINA being blocked by an upper-air ridge (as alluded to above), the last weather-related mechanism we need to consider is the expected arrival of a surface ridging high, around the southern tip of the continent, introducing fresh southerly to south-easterly airflow along the eastern seaboard (including KwaZulu-Natal) of South Africa, between Monday and Tuesday (as per figures 4 and 5 below). This is likely to sustain and enhance the heavy rain conditions along the KwaZulu-Natal coastline and interior, thus exacerbating the effects of an already severe weather pattern.
Figure 3. ECMWF predicted 12hour rainfall for midday, Sunday 4 March 2012 (in mm)
Figure 4. ECMWF predicted 12hour rainfall for midday, Monday 5 March 2012 (in mm)
Figure 5. ECMWF predicted 12hour rainfall for midday, Tuesday 5 March 2012 (in mm)
The South African Weather Service further wishes to state that the public can rest assured that the situation will continue to be closely monitored 24/7 throughout the weekend and beyond.
Further updates regarding this weather system will be issued at regular intervals to keep the public informed.
What common-sense precautions should I take?
- Avoid crossing strongly-flowing / flooded rivers at causeways or drifts (this advice is equally valid for pedestrians as well as motorists).
- Dwellings very close to rivers or within floodplains should be evacuated timeously (Farmers would be best advised to move river water pumps to higher ground).
- Small to medium sized boats and fishing craft (operating along the coastline mentioned above) should return to port timeously.
- Small fishing boats should be moved well above the normal high-water mark and firmly secured, as storm surge can be expected to raise local sea-levels by as much as 15 to 18 feet (3 to 6 m), particularly on the southern (poleward) side of the tropical storm.
ENDS
Issued by:
South African Weather Service (SAWS)
SAWDOS: Congratulations to the SAWS for getting the severe weather message out well in advance of the approaching storm. The public should take note of the above media release and take the necessary precautions to protect themselves and their property if at all possible. It would appear that TS Irina could be worse the TS Dando. Time will tell whether this will be the case.
Thursday, 16 February 2012
DISASTERS: Smart weather data can make a difference
Farmers are increasingly uncertain about when to plant
NAIROBI, 15 February 2012 (IRIN) - “When should we plant?” is a question increasingly being asked by small farmers in sub-Saharan Africa who depend on rain-fed agriculture. To help answer such questions, climate scientists are being urged to provide more reliable and relevant local climate data, and better communicate their knowledge on climate adaptation techniques.
"When we think about preparing for imminent disasters it is not possible to prepare for flooding, for example, just a few days in advance, which we get from the weather forecast. We need to think about preparedness further in advance and think in terms of what kind of decisions we can make, say, three months in advance, such as moving important resources away. We need a continuum of information,” said Simon Mason, the chief climate scientist at Columbia University's International Research Institute (IRI) in the USA.
According to Mason, more effective short, mid-range and seasonal weather forecasting is needed for the development of useful early warning systems.
Spatial weather tools, including satellite imagery and weather forecasts, allow the processing of weather data over different space and time frames. By allowing better integration of historical data with real-time weather data, such tools can improve the accuracy and impact of forecasts.
“If we are using projections of what will happen in 80 years to plan for the next 10 years, then we will have very bad information,” he said. “We have to match the kind of climate information we have with our decision-making time frames… For [climate] adaptation, we are much more interested in what is going to happen in the next few years,” he said.
Mason was speaking at a recent forum on disaster risk management at which a partnership between the UN International Strategy for Disaster Reduction (ISDR) and the African Centre of Meteorological Applications for Development (ACMAD) was launched. The partnership is aimed at facilitating the linkage between climate scientists and disaster risk managers as well as policymakers.
“There is a need to convert the information coming from scientists into usable material such as maps… There is a need to strengthen more partnerships with regard to climate change in the Horn of Africa region,” said ISDR Africa head Pedro Basabe.
Poor linkages in the past have meant that climate research does not necessarily inform policy for disaster mitigation: Complicated, long-range climate projections are often hard to sell to policymakers.
“We are fairly renowned for being incomprehensible to everybody," said Mason.
User-friendly data
To help make climate data more palatable, the World Meteorological Organization's Global Framework for Climate Services (GFCS) is helping with capacity-building in regional climate bodies such as ACMAD, the Inter-Governmental Authority on Development (IGAD), and the Climate Predication and Applications Centre (ICPAC). This in turn can assist national bodies produce customized information that is more relevant for communities.
Communication training workshops with climate scientists are also planned.
“There is a need to provide the science in summary for the policymakers. We need to try [to] communicate science in a more simple and relevant manner," said Maarten van Aalst, director of the Red Cross/Red Crescent Climate Centre.
In a situation where climate projections are fraught with uncertainty, van Aalst said: “We need to plan [for disasters] in as practical circumstances as possible, even in anticipation of better information.”
- IRIN
Tuesday, 14 February 2012
East Africa should be prepared for further food insecurity –weather forecasters
NAIROBI (AlertNet) – East Africa, still battling a hunger crisis, should be prepared for another dry spell and further food insecurity due to the persistence of La Niña weather conditions that last year brought severe drought to the region, weather forecasters have warned.
“La Niña conditions are expected to persist until March to May 2012,” the World Meteorological Office said on its website on Sunday.
March to May is the main ‘long rains’ season for the region, which farmers and livestock herders depend upon for crops and pasture to grow and for water sources to replenish.
“Given extreme food insecurity during 2011 and the possibility of a poor March‐May season in the eastern Horn of Africa, humanitarian partners should prepare contingency plans that could quickly address any disruptions to crop/livestock production and household food access that may occur,” said the Famine Early Warning Systems Network in its latest update.
Some 13 million people in the Horn of Africa went hungry last year after severe drought hit the region.
There has been a weak-to-moderate La Niña – a phenomenon causing a cooling of the Pacific Ocean – from October and it is currently near its maximum strength, WMO said.
However, historical precedence and forecast models suggest this La Niña is weaker than the 2010-2011 event, it added.
FEWSNET describes the probability of below-normal rainfall as “moderate”.
“There may also be a delay in the onset of the rains,” it said.
Crops that take several months to mature – such as Kenya’s staple food, maize – do not do well when rains are late.
- AlertNet
“La Niña conditions are expected to persist until March to May 2012,” the World Meteorological Office said on its website on Sunday.
March to May is the main ‘long rains’ season for the region, which farmers and livestock herders depend upon for crops and pasture to grow and for water sources to replenish.
“Given extreme food insecurity during 2011 and the possibility of a poor March‐May season in the eastern Horn of Africa, humanitarian partners should prepare contingency plans that could quickly address any disruptions to crop/livestock production and household food access that may occur,” said the Famine Early Warning Systems Network in its latest update.
Some 13 million people in the Horn of Africa went hungry last year after severe drought hit the region.
There has been a weak-to-moderate La Niña – a phenomenon causing a cooling of the Pacific Ocean – from October and it is currently near its maximum strength, WMO said.
However, historical precedence and forecast models suggest this La Niña is weaker than the 2010-2011 event, it added.
FEWSNET describes the probability of below-normal rainfall as “moderate”.
“There may also be a delay in the onset of the rains,” it said.
Crops that take several months to mature – such as Kenya’s staple food, maize – do not do well when rains are late.
- AlertNet
Tuesday, 7 February 2012
Kenyan drought puts traditional weather forecasters on the defensive
Traditional weather forecasting elders in northern Kenya's Marsabit district meet to discuss problems with their predictions following unexpectedly severe drought. ALERTNET/Abjata Khalif
MARSABIT, Kenya (AlertNet) – Nomadic communities living off the dry terrain of northern Kenya have relied for generations on the powers of village elders to predict the weather. But the divinations of traditional forecasters were confounded by an unexpectedly severe drought in 2011, threatening herders’ livelihoods.
Now pastoralists and meteorological experts are trying to find better ways to cope with regional weather that is increasingly difficult to anticipate - a situation some believe is linked to climate change.
Herders in Marsabit district use traditional weather forecasting systems linked to the seasons and the calendar. These include phenology (the study of plant and animal life cycles), animal behaviours, astrology, studying animal entrails and divining.
Elders detect changes in temperature and humidity from a tree locally known as the marer. They observe the migratory patterns of species of birds, and trace the progress of stars in the sky or look for the presence of particular stars in constellations.
In the belief system of the Marsabit communities, all this information can be used to forecast particular weather events such as long or short periods of rainfall, flash flooding, dry spells, or cold weather that could cause illness in people and livestock. The level of pasture in the region can also be foretold on this basis.
When the elders predict a dry spell, herders may move to other areas with more water and pasture, or even cross the border into Ethiopia, to return once the situation has improved. They may sell their goats, sheep and cattle and buy camels, which are better able to withstand drought. Others slaughter their older cattle and preserve the meat to use as food during the dry period.
FAILURE OF PREDICTED RAINS
Using their traditional forecasting systems, the elders in Marsabit district predicted that rains would fail in the area from October or November 2010 until April 2011, but that after this dry spell the situation would return to normal. This information was relayed to the community through the network of traditional elders in every village in the district.
As anticipated, there were only erratic rains towards the end of 2010, and then a dry period. But the onset of rain predicted for April never occurred, and the situation rapidly turned catastrophic.
With livestock weakened, pasture diminished and the water running dry for people and livestock, thousands of herders crossed into southern Ethiopia in search of water and pasture, while others fled remote villages for towns in search of food and pasture.
Abdi Boru, from the Turbi area of Marsabit, said he lost 23 head of cattle in the drought, leaving him with just two.
“The situation changed to worse from (what the elders) predicted and everybody started losing livestock in high numbers. We could not move them across the border as they were weak, and we watched while they died,” said Boru.
When rains finally came in November 2011, they were so heavy that there was flash flooding, which the traditional forecasters also failed to predict.
Kunu Halakano, an elder in Dambalfanchana village, said he was shocked by the turn of events.
“We have given our community weather information for many years, and that assisted them in understanding what to expect and plan, but now I am seeing something else from what we predicted. We predicted good rains after the dry spell and (yet) the rains failed from April to October,” said Halakano.
The forecaster blamed the failure of the traditional predictions on powers beyond the elders’ knowledge and systems. Elders have met repeatedly to discuss what happened, and some say the problem lay with insufficient attention to signs in the natural world.
Boru Duba, an elder from Dirib Gombo village, said that he had predicted the dry spell from October to April based on the behaviour of cattle and sheep, particularly their lack of interest in mating, strange noises they had been making, and the cattle coiling their tails.
“These scenarios perfectly matched the dry spell or minor droughts that hit the region occasionally from October to April. The last time we saw this minor drought was 10 years ago, and the situation then returned to normal,” said Duba.
But he said that the elders had not properly taken into account other telltale signs, such as the non-appearance of certain migratory birds, and the failure of frogs to make certain noises at the time that the birds would normally arrive.
“Without these signs and behaviours from the birds and frogs, I knew something was amiss in our prediction,” said Duba.
Despite the failure of the forecast, pastoralists’ strong cultural ties to traditional systems of forecasting make them reluctant to stop believing in them.
“I still respect the traditional weather system and I will always follow (the elders’) advice. They have offered us valuable weather information during the worst drought periods like that the ones in 1984, 1992 and 2005, and their prediction was right,” said Abdi Boru.
“They have already told us the problem that caused the wrong prediction and I hope it will never happen again,” he added.
INTEGRATING PREDICTION
Development organisations within Marsabit district recognise that the belief in traditional systems is unlikely to be abandoned. In response, they are urging relevant agencies to team up with local elders in order to integrate their knowledge with current early warning systems that can produce accurate and timely information.
Kenya’s ministry overseeing the development of the north and other arid lands is now working with the country’s meteorological department to map the traditional system of weather forecasting with a view to mainstreaming it with the department’s modern system.
Integrated weather forecasts can be broadcast to the pastoralist communities through community radio in local languages, providing consistent information to each village. Officials believe that this approach will work as long as it does not downplay the traditional systems and ensures that their data are respected and reflected in the forecasting.
Tari Konso of Pastoralist Development Agencies, a local non-governmental organisation, said, “Such integrated collaboration could save lives, prevent displacements, save herds of livestock from decimation and reduce suffering to manageable levels.”
- AlertNet
Wednesday, 4 January 2012
Weather erratic for Brazil soy as harvesting starts
BRASILIA (Reuters) - Heavy showers will sweep over central and northeastern soy regions in Brazil this week but little moisture will reach the critically dry south, forecaster Somar said on Tuesday, as some farmers fire up harvesters to start gathering the crop.
The world's No. 2 soy producer is now well into the wet summer season. But the La Nina weather anomaly has disrupted rainfall patterns in the south, keeping that region and neighboring Argentina's soy areas mostly dry in recent weeks.
The drought has already destroyed some of the corn planted in Parana state, the country's biggest corn state, and relief from dryness will be critical in the next week or two in No. 3 soy grower Rio Grande do Sul in the far south to prevent seed germination failing.
Dryness there and in world No. 3 producer Argentina, has given support to soybean futures in recent days, with no sign of imminent relief.
As of 10:31 a.m. CST (1631 GMT), the Chicago futures exchange's March contract , now the most active, traded up 24 cents at $12.31-3/4 per bushel. March corn was up 9-1/2 cents at $6.56 a bushel.
Brazil's top soy state, Mato Grosso has largely been spared the weather chaos facing other important states. In a weekly crop bulletin, Somar said its soy productivity looked "close to the maximum" as the first harvesting gets going there. The state is set to receive more rain in central and northern parts, but it will need mostly dry weather as harvesting quickens.
Further south in Parana, Brazil's No. 2 state for soy, the crop also looked in good shape, Somar said, though the current dry spell was likely to cut productivity. The drought has already caused widespread damage to Parana's corn crop.
In its extended forecast, Somar said rains would move a little to the south between January 7-11, bringing a total of 15-30 millimeters (0.6-1.2 inches) to the very dry states of Parana, Mato Grosso do Sul and Rio Grande do Sul. The heavy rain bound this week for states in the east of the country would also ease after a day or two.
- Reuters
The world's No. 2 soy producer is now well into the wet summer season. But the La Nina weather anomaly has disrupted rainfall patterns in the south, keeping that region and neighboring Argentina's soy areas mostly dry in recent weeks.
The drought has already destroyed some of the corn planted in Parana state, the country's biggest corn state, and relief from dryness will be critical in the next week or two in No. 3 soy grower Rio Grande do Sul in the far south to prevent seed germination failing.
Dryness there and in world No. 3 producer Argentina, has given support to soybean futures in recent days, with no sign of imminent relief.
As of 10:31 a.m. CST (1631 GMT), the Chicago futures exchange's March contract , now the most active, traded up 24 cents at $12.31-3/4 per bushel. March corn was up 9-1/2 cents at $6.56 a bushel.
Brazil's top soy state, Mato Grosso has largely been spared the weather chaos facing other important states. In a weekly crop bulletin, Somar said its soy productivity looked "close to the maximum" as the first harvesting gets going there. The state is set to receive more rain in central and northern parts, but it will need mostly dry weather as harvesting quickens.
Further south in Parana, Brazil's No. 2 state for soy, the crop also looked in good shape, Somar said, though the current dry spell was likely to cut productivity. The drought has already caused widespread damage to Parana's corn crop.
In its extended forecast, Somar said rains would move a little to the south between January 7-11, bringing a total of 15-30 millimeters (0.6-1.2 inches) to the very dry states of Parana, Mato Grosso do Sul and Rio Grande do Sul. The heavy rain bound this week for states in the east of the country would also ease after a day or two.
- Reuters
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