000 AXNT20 KNHC 040005 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT FRI OCT 03 2008 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND 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. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 18W/19W S OF 17N MOVING W NEAR 10 KT. COMPUTER MODEL GUIDANCE SHOWS ENHANCED LOW LEVEL CIRCULATION COINCIDING WITH THE WAVE AXIS...WHERE DEEP LAYER MOISTURE IS MAXIMIZED BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. ISOLATED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF THE WAVE AXIS. TROPICAL WAVE IS ALONG 47W/48W S OF 17N MOVING W NEAR 10 KT. WAVE IS EMBEDDED WITHIN AN AREA OF ENHANCED DEEP LAYER MOISTURE. COMPUTER MODEL GUIDANCE DEPICTS LOW LEVEL CIRCULATION ALONG WAVE AXIS. ISOLATED SHOWERS ARE OCCURRING WITHIN 150 NM W OF THE WAVE AXIS N OF 12N. TROPICAL WAVE IS ALONG 58W/59W S OF 17N MOVING W 10-15 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN CIMSS WAVETRACK DERIVED LOW LEVEL CIRCULATION...AS WELL AS A MAXIMUM IN TOTAL PRECIPITABLE WATER. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF THE WAVE AXIS N OF 13N...WITH ISOLATED MODERATE CONVECTION WITHIN 90 NM EITHER SIDE OF THE WAVE AXIS S OF 10N. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 13N16W 9N25W 8N40W 11N52W 10N63W. ISOLATED MODERATE CONVECTION IS OVER W AFRICA FROM 11N-16N BETWEEN 15W-18W...INCLUDING GUINEA-BISSAU...GAMBIA...AND SENEGAL. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 150 NM N OF THE AXIS AND 210 NM S OF THE AXIS FROM THE W AFRICAN COAST TO 31W. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM S OF THE ITCZ AXIS FROM 61W WESTWARD TO THE SOUTH AMERICAN COAST...IMPACTING NE VENEZUELA AND N GUYANA. ...DISCUSSION... GULF OF MEXICO... DRY AND STABLE AIR IN THE BASE OF A BROAD UPPER TROUGH IS OVER THE GULF REGION AND E CONUS...WITH STRONG WESTERLY FLOW ALOFT OVER THE N GULF. SUBSIDENCE RESULTING FROM A WEAK SURFACE RIDGE OVER THE N GULF IS ALSO HELPING TO RESULT IN FAIR WEATHER ACROSS MUCH OF THE GULF. A STATIONARY FRONT EXTENDS FROM JUST NW OF CUBA NEAR 22N84W NE TO 24N80W TO THE SW ATLC. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE FRONT...WHERE GREATER ATMOSPHERIC LIFT AND DEEP MOISTURE PERSISTS. CARIBBEAN SEA... OVER THE W CARIBBEAN...A WEAK UPPER HIGH IS NEAR 17N82W...WITH MOIST DIFFLUENT UPPER FLOW TO THE E OF THIS HIGH. ALSO OVER THE W CARIBBEAN...A SURFACE TROUGH EXTENDS FROM W NICARAGUA NEAR 12N87W TO A 1011 MB SURFACE LOW IN THE GULF OF HONDURAS NEAR 17N86W TO 20N85W. SATELLITE IMAGERY DEPICTS A BROAD LOW LEVEL CIRCULATION IN THE VICINITY OF THE SURFACE LOW AND TROUGH. SURFACE CONVERGENCE AND UPPER DIFFLUENCE NEAR THESE FEATURES ARE RESULTING IN SCATTERED MODERATE/ISOLATED STRONG CONVECTION OVER THE W CARIBBEAN W OF 77W...INCLUDING JAMAICA...CUBA... HONDURAS...AND NICARAGUA. A WEAK UPPER RIDGE IS OVER THE CENTRAL CARIBBEAN...WHERE MAINLY FAIR WEATHER IS PRESENT. OVER THE E CARIBBEAN...AN UPPER LOW IS CENTERED JUST W OF THE LEEWARD ISLANDS NEAR 16N63W...WITH A WEAK UPPER TROUGH EXTENDING TO THE SW OF THE LOW TO NW VENEZUELA. MOIST SOUTHERLY FLOW ALOFT COMBINED WITH THE TROPICAL WAVE ALONG 58W/59W IS RESULTING IN ISOLATED SHOWERS OVER THE E CARIBBEAN E OF 63W AND N OF 15N...WHICH ARE IMPACTING THE LEEWARD ISLANDS. ATLANTIC OCEAN... STRONG SOUTHWESTERLY FLOW ALOFT E OF A DEEP TROUGH OVER THE E CONUS IS IMPACTING PORTIONS OF THE SW ATLC. A COLD FRONT EXTENDS FROM A 1013 MB SURFACE LOW NEAR 32N73W SW TO NEAR 27N77W. THIS FRONT EXTENDS FURTHER TO THE SW AS A STATIONARY FRONT TO 24N80W TO 23N84W. DRY AND STABLE AIR IN THE BASE OF THE UPPER TROUGH CONTINUES TO AFFECT THE SW ATLC TO THE NW OF THE SURFACE FRONT...WITH LINGERING MOISTURE AND ATMOSPHERIC LIFT ALONG AND SE OF THE FRONT. AS A RESULT...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE WITHIN 180 NM SE OF THE SURFACE FRONT... AFFECTING CUBA AND THE BAHAMAS. TO THE E...AN UPPER HIGH IS CENTERED NEAR 32N57W...WITH ITS ASSOCIATED UPPER RIDGE EXTENDING FROM THE HIGH INTO THE CENTRAL CARIBBEAN. THIS HIGH AND RIDGE ARE RESULTING IN DRY AND STABLE ATMOSPHERIC CONDITIONS OVER MUCH OF THE CENTRAL ATLC. FARTHER TO THE E...A COMPACT AND DEEP LOW IS CENTERED NEAR 22N46W WITH AN UPPER TROUGH EXTENDING NE OF THE THE LOW TO NEAR 29N37W. THESE FEATURES ARE SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 32N44W S TO 28N44W TO 24N44W. DEEP LAYER DRY AIR OVER THE SURFACE TROUGH IS INHIBITING CONVECTION NEAR MUCH OF THE SURFACE TROUGH. HOWEVER...TO THE S OF THIS SURFACE TROUGH...SAHARAN AIR LAYER CONTINUES TRACKING TO THE W INTO A MOIST AIRMASS. LOW LEVEL CONVERGENCE AT THE BOUNDARY IS SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN 150 NM OF A LINE FROM 20N44W S TO 15N38W TO 10N36W...WHICH IS BEING ENHANCED BY LIFT IN SW FLOW ALOFT. FARTHER TO THE E...A BROAD UPPER TROUGH IS N OF 23N BETWEEN THE W AFRICAN COAST AND 35W...WITH DRY AIR EMBEDDED WITHIN THIS TROUGH. OVER THE TROPICAL ATLC...A BROAD E/W UPPER RIDGE EXTENDS FROM W AFRICA ALONG 12N TO 52W AND DOMINATES THE THE TROPICAL ATLC. $$ COHEN