000 AXNT20 KNHC 050555 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SAT APR 05 2008 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0430 UTC. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 6N11W 3N20W 1N30W CROSSING THE EQUATOR AT 40W TO 1S45W. SCATTERED STRONG CONVECTION WITHIN 300 NM EITHER SIDE OF AXIS BETWEEN 24W AND 33W. SCATTERED MODERATE FROM EQUATOR TO 2N BETWEEN 44W AND 48W. ...DISCUSSION... GULF OF MEXICO... A SOUTHERN STREAM SHORTWAVE TROUGH PASSING THROUGH THE SOUTHERN PLAINS IS RESPONSIBLE FOR A WEAK COLD FRONT ENTERING THE NW GULF OF MEXICO AND FAR NE MEXICO. ALTHOUGH AN EARLIER QUIKSCAT PASS REVEALED NE 20- TO 25-KT WINDS BEHIND THE FRONT...MUCH OF THE DATA APPEARED TO BE RAIN-CONTAMINATED AND THUS NOT CONSIDERED RELIABLE. HOWEVER...A COMBINATION OF COASTAL...CMAN...AND BUOY OBSERVATIONS DO CONFIRM N TO NE WINDS OF 20 TO POSSIBLY 25 KT DIRECTLY BEHIND THE FRONT. RADAR AND SATELLITE IMAGERY SHOWS SCATTERED TO LOCALLY NUMEROUS TSTMS WITHIN 90 NM NW OF THE FRONT IMMEDIATELY OFFSHORE THE UPPER TX AND SW LA COASTS...N OF WHAT COULD BE A WEAK 1007 MB SFC LOW ANALYZED NEAR 29N93W. ELSEWHERE E OF THE FRONT...SE TO S WINDS OF 15 TO 20 KT COVER THE GULF... WITH SKIES REMAIN MOSTLY CLOUD FREE EXCEPT FOR SOME ISOLATED CONVECTIVE CELLS SPROUTING UP OVER THE FAR NE. SHORT-TERM MODEL GUIDANCE SHOWS THE SOUTHERN PLAINS SHORTWAVE BEGINNING TO LIFT OUT OVER THE SE U.S. LATE SAT...UNABLE TO DIG MUCH FURTHER THANKS TO A FAIRLY SOLID MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC. DESPITE THIS...A BROAD PATTERN OF UPPER-LEVEL DIVERGENCE...WARM AIR ADVECTION...AND POSITIVE VORTICITY ADVECTION AHEAD OF THE SYSTEM SHOULD RESULT IN FAIRLY WIDESPREAD CONVECTIVE RAINS NOT ONLY OVER THE SOUTHERN TIER AND GULF COAST BUT ALSO OVER THE NORTHERN GULF WATERS THROUGH MUCH OF SAT. HOWEVER...WITH THE UPPER SUPPORT ALREADY PUSHING NE AND THE MID- TO UPPER-LEVEL BECOMING NEARLY PARALLEL ALONG THE FRONT...EXPECT THE FRONT TO STALL NEARLY HALFWAY ACROSS THE GULF WITH A NE-SW ORIENTATION. WHAT IS LEFT OF THE FRONT SHOULD RETREAT AS A WARM FRONT SUN INTO MON...LYING CLOSE TO OR JUST INLAND FROM THE GULF COAST. CARIBBEAN SEA... WATER VAPOR IMAGERY REVEALS HIGH-LEVEL WESTERLY FLOW DOMINATING MUCH OF THE BASIN...WITH A WEAK MID- TO UPPER-LEVEL TROUGH EXTENDING FROM 21N79W INTO THE E PACIFIC W OF COSTA RICA. MODERATE TO STRONG SUBSIDENCE ASSOCIATED WITH A LARGE MID- TO UPPER-LEVEL ANTICYCLONE IN THE TROPICAL E PACIFIC IS OBSERVED AS FAR E AS THE WESTERN CARIBBEAN W OF THE TROUGH AXIS. HOWEVER...A PLUME OF MOISTURE WITH ORIGINS FROM THE AMAZON IS BEING DRAWN NORTHWARD OVER THE CENTRAL CARIBBEAN E OF THE TROUGH AXIS. THIS SUBTLE INCREASE IN UPPER TROPOSPHERIC MOISTURE AND THE DIFFLUENT UPPER-LEVEL FLOW HAS HELPED TO EXCITE SOME CONVECTION...ALTHOUGH WHAT HAS FORMED IS PRETTY SCARCE. IN FACT...ONLY SPORADIC CONVECTIVE ELEMENTS ARE NOTED FROM PANAMA THROUGH NORTHERN COLOMBIA...ALL OF WHICH ARE GRADUALLY DIMINISHING. SCATTERED LATE AFTERNOON CONVECTION...LIKELY A RESULT OF LOCAL SEA BREEZE CIRCULATIONS ...ALSO CONTINUES TO WIND DOWN OVER CUBA. OTHERWISE...STRONG HIGH PRESSURE OVER THE CENTRAL ATLANTIC HAS AN EXTENSION INTO THE CARIBBEAN SEA AND IS PROVIDING FRESH TRADES ACROSS THE EASTERN AND PARTS OF THE CENTRAL PART OF THE AREA. HOWEVER...REAL-TIME NCEP RE-ANALYSIS DATA INDICATES THAT CURRENT TRADES ARE FAIRLY CHARACTERISTIC OF THIS TIME OF THE YEAR...EXCEPT PERHAPS SLIGHTLY STRONGER-THAN-NORMAL OVER THE FAR E. OVER THE NEXT FEW DAYS...A WELL-DEFINED MID- TO UPPER-LEVEL RIDGE SHOULD SET UP SHOP N OF THE CARIBBEAN...IN THE VICINITY OF 25N62W...WHILE THE TROUGH CURRENTLY OVER THE WESTERN CARIBBEAN MOVES W AND LOSES ITS IDENTITY. THIS SHOULD SET UP A PATTERN OF LIGHT UPPER-LEVEL WINDS ACROSS THE AREA...WITH SUBSTANTIAL EASTERLY WIND ANOMALIES LIKELY FROM THIS WEEKEND INTO EARLY NEXT WEEK. MEANWHILE...THE STRONG SURFACE RIDGE NOW NEAR 36N54W SHOULD WEAKEN AND SHIFT SE TO 28N62W BY EARLY MON...WHICH SHOULD ALLOW TRADES TO RELAX OVER THE EASTERN AND CENTRAL CARIBBEAN. ATLANTIC OCEAN... AN ANOMALOUSLY STRONG MID-LEVEL RIDGE REMAINS LOCKED IN PLACE OVER THE WESTERN ATLANTIC NEAR 25N62W...DIRECTING THE STRONGER MID-LATITUDE FLOW OVER THE EASTERN CONUS N OF THE AREA. MUCH OF THE STRONGER MID-LATITUDE FLOW DIGS EASTWARD INTO A BROAD MID- TO UPPER-LEVEL TROUGH W OF 50W AND N OF 15N...WITH AN ASSOCIATED DEEP-LAYERED CYCLONIC CIRCULATION CLOSE TO 39N36W. W OF THE TROUGH...A LARGE DOME OF SURFACE HIGH PRESSURE IS CENTERED NEAR 36N54W AND DOMINATES MUCH OF THE ATLANTIC...IN SOME CASES WITH ENHANCED TRADES. IN FACT...AN EARLIER QUIKSCAT PASS REVEALED NE TO E WINDS OF 20- TO 25-KT OVER A LARGE EXPANSE S OF 20N AND E OF THE LESSER ANTILLES TO ABOUT 40W....WITH SEAS GENERALLY 10 TO 13 FT IN NE SWELL. THE ABOVE PATTERN SHOULD CONTINUE INTO THE WEEKEND...WITH THE TRADES SLOWLY DIMINISHING TO CLIMATOLOGICAL LEVELS AND SEA GRADUALLY SUBSIDING. W OF 50W...A BROAD SURFACE CYCLONIC FLOW COVERS THE AREA N OF 25N...WITH A SURFACE COLD FRONT LOCATED FROM 31N38W TO 28N46W TO 30N56W. THE FRONT IS MARKED BY THE LEADING EDGE OF A FAIRLY DENSE STRATOCUMULUS DECK OF CLOUDS...THOUGH THERE IS LITTLE ELSE ALONG THE IMMEDIATE FRONT. AS THE FRONT RACES SE SAT...THE INJECTION OF COOLER AIR SHOULD BRIEFLY RE-INVIGORATE THE LARGE CYCLONIC CENTER NEAR THE SE AZORES...WHICH SHOULD REINFORCE THE CYCLONIC FLOW OVER THE NE PART OF THE AREA. ELSEWHERE...WATER VAPOR IMAGERY AND CLOUD-TRACKED WINDS INDICATE A NARROW RIDGE S OF ABOUT 12N FROM THE NW COAST OF AFRICA TO JUST SE OF THE ANTILLES. THE DEEP EASTERLIES S OF THE RIDGE AXIS HAVE BEEN PROVIDING A FAVORABLE ENVIRONMENT FOR ENHANCED CONVECTION ALONG THE ITCZ THE LAST FEW DAYS...AND THIS PATTERN OF ANOMALOUS EASTERLY FLOW SHOULD CONTINUE FOR THE NEXT FEW DAYS. $$ KIMBERLAIN