000 AXNT20 KNHC 152355 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU MAR 15 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS... WEATHER OBSERVATIONS...AND RADAR. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 7N12W 3N20W THEN BECOMES ALIGNED WITH THE EQUATOR W TO S AMERICA AT 48W. THE AXIS IS MUCH LESS ACTIVE THAN 24 HRS AGO WITH MOST OF THE ACTIVITY CONCENTRATED OVER THE FAR WRN PORTION WHERE SCATTERED STRONG IS OCCURRING WITHIN 60 NM N OF THE AXIS W OF 45W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE ELSEWHERE WITHIN 180 NM N OF THE AXIS BETWEEN 22W-40W. ...DISCUSSION... GULF OF MEXICO... A WELL PRONOUNCED MID/UPPER LEVEL LOW MOVING E 20-25 KT IS LOCATED OVER THE EXTREME SRN PORTION OF MISSISSIPPI. THE LOW IS EMBEDDED IN A DEEP LAYERED TROUGH THAT EXTENDS FROM THE UPPER GREAT LAKES SWD ACROSS ALABAMA AND ACROSS THE E GULF THROUGH 27N86W TO THE NE YUCATAN PENINSULA. ITS ASSOCIATED SURFACE LOW WAS ANALYZED JUST SW OF MOBILE BAY AT 2100 UTC. AN ATTENDED TROUGH EXTENDS SW FROM THE LOW THROUGH 27N90W TO NEAR 26N97W. THE COMBINATION OF THE SURFACE TROUGH ALONG WITH UPPER LEVEL DIFFLUENCE FOUND AHEAD OF THE LOW AND A VERY MOIST SLY FLOW PRESENT E OF THE TROUGH CONTINUES TO RESULT IN SCATTERED TO NUMEROUS TSTMS OVER THE NE GULF... WITH THE ACTIVITY PRIMARILY TIED TO A VIGOROUS FAST MOVING SQUALL LINE THAT EXTENDS FROM APALACHEE BAY SW TO NEAR 27N88W. THE REMAINDER OF THE GULF IS FAIRLY TRANQUIL UNDER MODERATE TO STRONG SUBSIDENCE AND ASSOCIATED DRY AIR ALOFT. OVER THE NEXT COUPLE OF DAYS...THE UPPER LOW WILL MOVE ESE AND WEAKEN. NWP MODELS SHOW A RATHER QUICK MOVING UPPER TROUGH DEVELOPING AND SWINGING THROUGH THE REGION ON FRI AND INTO EARLY SAT. THIS UPPER FEATURE IS FORECAST TO QUICKLY SWING A SFC FRONT ACROSS THAT WILL MOST LIKELY BE ACCOMPANIED BY A LINE OF SCATTERED TO NUMEROUS SHOWERS AND TSTMS. CARIBBEAN... BROAD FLAT RIDGING HAS SETTLED IN ACROSS MUCH OF THE CENTRAL AND ERN PORTIONS OF THE CARIBBEAN WITH UPPER LEVEL SW-W WINDS NOTED ON SATELLITE DERIVED UPPER AIR DATA. MODERATE SUBSIDENCE AND ASSOCIATED DRY AIR IS EVIDENT ACROSS JUST ABOUT THE ENTIRE SEA. IN THE LOWER LEVELS...THE TAIL END OF A STUBBORN TROUGH EXTENDS SW FROM THE ATLANTIC TO EXTREME NE PART OF THE SEA IN THE VICINITY OF THE LEEWARD ISLANDS. SLIGHT LOW-LEVEL CONVERGENCE NEAR THIS SLOWLY WEAKENING BOUNDARY IS PRODUCING PATCHES OF SHALLOW CLOUDS WITH ISOLATED SHOWERS MOSTLY WITHIN 120 NM N OF THE SFC TROUGH. RESIDUAL LOW LEVEL CLOUDINESS FROM THIS TROUGH IS MOVING WSW IN MODERATE TO FRESH NE-E TRADES PRODUCED BY STRONG SFC HIGH PRES LOCATED N OF THE DISCUSSION AREA. ISOLATED SHOWERS ARE EMBEDDED WITHIN THESE CLOUDS FROM 15N-17N E OF 76W. OVER THE NEXT COUPLE OF DAYS...THE STRONG SFC RIDGE AND TROUGH WILL SHIFT SLIGHTLY TO THE E. THIS WILL ALLOW THE TRADE WINDS TO SLACKEN AND GRADUALLY THIN THE FETCH OF MOISTURE ACROSS THE ERN CARIB. MEANWHILE...A COLD FRONT IS FORECAST TO ENTER THE NW CARIBBEAN LATE FRI INTO SAT WITH INCREASING MOISTURE ALONG AND TO ITS E. THE FRONT IS THEN EXPECTED TO WEAKEN IN THE VICINITY OF THE WINDWARD PASSAGE SUN. WESTERN ATLANTIC... THE PATTERN HERE HAS NOT CHANGED MUCH SINCE YESTERDAY WITH A MID AND UPPER LEVEL RIDGE/TROUGH PATTERN MOVING SLOWLY E ACROSS THE ATLC. THE MID/UPPER LEVEL RIDGE IS ALIGNED FAIRLY N-S ALONG 70W. A THINNING PLUME OF HIGH LEVEL CLOUDS IS FOUND IN THE RIDGE AXIS...CURRENTLY N OF 22N BETWEEN 60W-77W. THIS UPPER MOISTURE QUICKLY DRIES OUT E OF 60W AS THE MID/UPPER LEVEL FLOW VEERS NWLY IN RESPONSE TO A WELL-DEFINED VERTICALLY STACKED OCCLUDED LOW N OF THE AREA NEAR 34N50W. IN FACT...THE AIR ALOFT IS VERY DRY BETWEEN 50W-61W WHERE UPPER CONFLUENCE IS QUITE STRONG. THIS LOW PRES SYSTEM HAS AN ASSOCIATED SLOW MOVING COLD FRONT THAT ENTERS THE AREA NEAR 32N47W AND EXTENDS SW TO 24N51W...WHERE IT THEN CONTINUES AS A WEAKENING SFC TROUGH TO THE NRN LEEWARD ISLANDS. SCATTERED SHOWERS AND TSTMS ARE WITHIN 180 NM AHEAD OF THE FRONT N OF 25N...AND ISOLATED TO SCATTERED SHOWERS AND ISOLATED WEAK TSTMS ARE WITHIN 120 NM ELSEWHERE EITHER SIDE FRONT/TROUGH. LOOKING AHEAD A DAY OR TWO...THE FRONT WILL SLOWLY BECOME DIFFUSE IN THE REGION AS THE STACKED LOW PRES SYSTEM...ITS SUPPORT...PULLS NE. AT THE SAME TIME THE NEXT COLD FRONT IS EXPECTED TO MOVE OFF THE U.S. EAST COAST FRI NIGHT. EASTERN ATLANTIC... BROAD DEEP RIDGING COVERS THE MAJORITY OF THE ATLC BETWEEN 30W- 55W...WITH A RIDGE AXIS ROUGHLY RUNNING THROUGH 8N55W 6N45W TO A MID/UPPER LEVEL ANTICYCLONE NEAR 5N36W AND TO 2N30W. DEBRIS MOISTURE FROM THE FRONT IN THE CENTRAL ATLC CONTINUES TO STREAM AROUND THE RIDGE TO 30W. THIS UPPER MOISTURE QUICKLY DRIES OUT E OF 30W AS THE MID/UPPER LEVEL FLOW VEERS NWLY IN RESPONSE TO A WEAKENING DEEP TROUGH STRETCHING FROM SPAIN THROUGH THE CANARY ISLANDS. A STRONG SFC HIGH CENTERED NEAR THE AZORES CONTINUES TO GENERATE A LARGE AREA OF MODERATE TO STRONG WINDS ACROSS THE REGION. IN THE DEEP TROPICS...THE UPPER LEVEL JETSTREAM BRANCH IS BEING SUPPRESSED SE EXTENDING FROM NEAR 6N30W TO 13N19W...AND NE TO INLAND ACROSS AFRICA. ABUNDANT MOISTURE EXISTS TO THE S AND E OF THE JET AXIS WHILE STRONG CONFLUENCE ALOFT ATTRIBUTED TO THE WEAKENING DEEP TROUGH MENTIONED ABOVE SIGNIFICANTLY DRIES THE AIR TO ITS N. OVER THE NEXT COUPLE OF DAYS...THE SFC HIGH WILL SLOWLY RETREAT NWD BUT SHOULD REMAIN IN CONTROL MAINTAINING THE WIDESPREAD FAIR WEATHER. $$ AGUIRRE