Cyclone Season 2012: Tropical Cyclone Irina (Southern Indian Ocean) 5 March 2012 11h30 SAST

050300Z POSITION NEAR 29.7S 34.7E.
TROPICAL CYCLONE (TC) 14S, (IRINA), LOCATED APPROXIMATELY 230 NM SOUTH-SOUTHEAST OF MAPUTO, MOZAMBIQUE, HAS TRACKED SOUTHWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS TC 14S BECOMING MORE SYMMETRIC AND DEVELOPING DEEPER CONVECTION. THE CURRENT INTENSITY IS BASED ON AVERAGE OF DVORAK ESTIMATES FROM PGTW, KNES, AND FMEE, AND SUPPORTED BY THREE SHIP REPORTS IN THE SOUTHEAST QUADRANT. A MOSAIC OF MICROWAVE IMAGES CULMINATING WITH A 042246Z TRMM PASS CONFIRMS MUCH BETTER ORGANIZATION, SHOWING THICK AND TIGHTLY CONVECTIVE BANDING AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC). THERE IS AN EXCEPTION IN THE FORM OF A LARGE BREAK OVER THE NORTHWEST QUADRANT, WHICH IS A RESULT OF SUBSIDENCE JUST NORTH OF THE SYSTEM. THE LATEST STREAMLINE ANALYSIS DEPICTS THE SUBSIDENT AREA AS THE PRODUCT OF AN UPPER LEVEL TROUGH, WHEREAS 24 HOURS AGO THERE WAS AN UPPER LEVEL CYCLONE IN THE SAME AREA. TOTAL PRECIPITABLE WATER LOOPS INDICATE DEEP MOISTURE IS RETURNING TO THE NORTHERN SEMICIRCLE AS THE CYCLONE FILLS. ANIMATED WATER VAPOR IMAGERY ALSO POINTS TO AN IMPROVING UPPER LEVEL ENVIRONMENT, SHOWING A VIGOROUS POLEWARD OUTFLOW CHANNEL TO THE SOUTHEAST AND SOLID RADIAL OUTFLOW ELSEWHERE. THE POLEWARD CHANNEL IS A PRODUCT OF AN ENCROACHING MID-LATITUDE TROUGH, WHICH IS NOW PASSING EASTERN SOUTH AFRICA. IN ADDITION TO FANNING THE OUTFLOW, THE TROUGH IS DRAWING TC 14S POLEWARD. IT STILL APPEARS THAT SEPARATION BETWEEN TC 14S AND THE MID-LATITUDE TROUGH IS OF SUFFICIENT DISTANCE TO PREVENT LINKAGE, AND THAT AS THE TROUGH PASSES DURING THE NEXT 24 HOURS, TC 14S WILL MAKE A LANGUID TURN BACK TO AN EQUATORWARD TRACK. AS THE SUBTROPICAL RIDGE REBUILDS OVER SOUTH AFRICA, IT WILL BECOME THE DOMINANT STEERING MECHANISM AND BEGIN GUIDING THE STORM BACK TOWARDS THE COAST OF SOUTHERN MOZAMBIQUE. MODEL GUIDANCE IS NOW IN NEAR UNANIMOUS AGREEMENT WITH THIS LOOPING PATTERN. THE ENVIRONMENT FOR TC 14S WILL REMAIN RELATIVELY STABLE DURING THIS PROCESS; HENCE THE FLAT TREND IN THE INTENSITY FORECAST. UPWELLING NEAR THE COAST WILL INDUCE SOME DECAY JUST PRIOR TO LANDFALL. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 050000Z
IS 18 FEET.

- JTWC + CIMSS