030300Z POSITION NEAR 25.5S 37.6E. TROPICAL CYCLONE (TC) 14S,(IRINA), LOCATED APPROXIMATELY 300 NM EAST OF MAPUTO, MOZAMBIQUE, HAS TRACKED WEST-SOUTHWESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS TC 14S IS STRUGGLING TO INTENSIFY EVEN THOUGH IT HAS MOVED INTO THE MIDDLE OF THE MOZAMBIQUE CHANNEL AND LIES DIRECTLY UNDERNEATH THE SUBTROPICAL RIDGE AXIS. THERE IS A SIGNIFICANT ABSENCE OF DEEP CONVECTION OVER THE NORTHERN SEMICIRCLE, AND SCATTEROMETRY DATA FROM 020912Z INDICATES THAT WINDS OVER THE EQUATORWARD SEMICIRCLE ARE GENERALLY BELOW GALE FORCE. A TOTAL PRECIPITABLE WATER LOOP CONFIRMS A LACK OF DEEP MOISTURE OVER THE CENTRAL CHANNEL AND A 021944Z TRMM IMAGE REVEALS THAT DEEP CONVECTION IS LIMITED TO THE SOUTHERN SEMICIRCLE. WATER VAPOR IMAGERY ALSO REVEALS THE STRONG SUBSIDENCE, SHOWING RESTRICTED OUTFLOW OVER THE NORTHWEST QUADRANT. THERE IS, HOWEVER, A SPECTACULARLY WELL-DEVELOPED EQUATORWARD CHANNEL SHUNTING MOISTURE DEEP INTO THE AFRICAN INTERIOR, WHICH WILL HELP SUSTAIN THE SYSTEM AT MINIMAL CYCLONE STRENGTH. THERE IS ALSO AN EXTENSIVE AREA OF GALE FORCE WINDS OVER THE SOUTHERN SEMICIRCLE, THE RESULT OF INTERACTION BETWEEN THE STORM AND A MIGRATORY MID-LATITUDE ANTICYCLONE. THE ANTICYCLONE IS MOVING RAPIDLY OUT OF THE AREA AND AS IT DOES SO A LOW- TO MID-LEVEL ANTICYCLONE ANCHORED OVER THE MASCARENE ISLANDS WILL BECOME THE DOMINANT STEERING FORCE, NUDGING THE STORM ACROSS THE CHANNEL TOWARDS SOUTHERN MOZAMBIQUE. DUE TO THE FAILURE OF THE SYSTEM TO INTENSIFY, RECENT MODEL GUIDANCE HAS BECOME MORE ERRATIC, WITH SOME VORTEX TRACKERS NOW INDICATING AN ERRATIC LOOPING MOTION OVER THE WESTERN CHANNEL. THE 021200Z PGTW UPPER LEVEL STREAMLINE ANALYSIS REVEALS THAT THE SOURCE OF THE SUPPRESSED DEVELOPMENT IS AN UPPER LEVEL CYCLONE JUST SOUTH OF THE RIDGE AXIS. ALTHOUGH LOW VERTICAL WIND SHEAR AND 29 DEGREE SEA SURFACE TEMPERATURES EXIST ALONG THE TRACK OF TC 14S, THE SUBSIDENCE ASSOCIATED WITH THE UPPER LEVEL CYCLONE WILL CAP INTENSITY AT LOW TROPICAL STORM STRENGTH AND THE LOW LEVEL STEERING ENVIRONMENT WILL REMAIN WEAK. THUS THERE IS A CHANGE TO THE FORECAST PHILOSOPHY AND TC 14S IS NOW EXPECTED TO TRACK WEST-SOUTHWESTWARD THROUGH TAU 36, THEN TURN BRIEFLY POLEWARD AS A MID-LATITUDE TROUGH TRACKS OFF-SHORE OF SOUTH AFRICA. THE SHALLOW DEPTH OF THE SYSTEM, HOWEVER, WILL PRECLUDE LINKAGE WITH THE MID-LATITUDE TROUGH AND TC 14S WILL RESUME A LANDWARD TRACK TOWARDS SOUTHERN MOZAMBIQUE AS THE NEXT ANTICYCLONE BUILDS OVER THE SOUTHERN MOZAMBIQUE CHANNEL. THE ANTICYCLONE WILL DRIVE TC 14S LANDWARD AS THE SYSTEM REMAINS AT AND JUST ABOVE CYCLONE INTENSITY THROUGH LANDFALL OVER SOUTHERN MOZAMBIQUE. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 030000Z IS 18 FEET.
- JTWC + SAT24.com
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