000 AXNT20 KNHC 272344 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT OCT 27 2007 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURE... AN AREA OF LOW PRESSURE...ANALYZED 1003 MB...IS CENTERED ABOUT 100 NM S OF HAITI NEAR 16N71W. THE LOW-LEVEL CIRCULATION IS FAIRLY WELL DEFINED BUT REMAINS EXPOSED TO THE W OF A LARGE CONVECTIVE MASS. BASED ON THIS ORGANIZATION...IT IS CLEAR THAT THIS SYSTEM IS FEELING SOME EFFECTS OF WLY SHEAR TO THE S OF AN UPPER LOW. CONVECTION HAS GENERALLY BEEN ON THE INCREASE THIS EVENING...NOW NUMEROUS MODERATE/SCATTERED STRONG IN NATURE...TO THE NE OF THE CENTER FROM 16N-18N BETWEEN 68W-71W. A LARGE RATHER MESSY AREA OF SCATTERED MODERATE CONVECTION EXISTS ELSEWHERE FROM 12N-19N BETWEEN 61W-74W...WHICH INCLUDES PUERTO RICO...THE VIRGIN ISLANDS AND THE LESSER ANTILLES. METAR AND BUOY DATA INDICATES THAT THIS LOW IS RATHER BROAD WITH MANY STATIONS IN THE CENTRAL AND E CARIB REPORTING AN SLP LOWER THAN 1008 MB. ANY INCREASE IN ORGANIZATION COULD LEAD TO THE FORMATION OF A TROPICAL DEPRESSION AND INTERESTS IN THE CENTRAL AND NORTHWESTERN CARIBBEAN SEA SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE THE AREA ON SUNDAY...IF NECESSARY. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 42W S OF 14N MOVING W 15 KT. THIS WAVE HAS GENERALLY CHANGED LITTLE OVER THE PAST DAY OR TWO. A NARROW BAND OF MOISTURE AND AREA OF LOW-LEVEL TURNING IS APPARENT ON SATELLITE IMAGERY. THE NRN PORTION OF THE WAVE IS BEGINNING TO TILT AS IT FEELS THE EFFECTS OF EXTENSIVE SWLY FLOW ASSOCIATED WITH A DEEP LAYER TROUGH TO ITS NNW. SCATTERED SHOWERS AND ISOLATED TSTMS ARE WITHIN 90 NM EITHER SIDE OF THE WAVE AXIS N OF 8N. TROPICAL WAVE IS ALONG 52W S OF 12N MOVING W 10-15 KT. NEARLY ALL OF THE ASSOCIATED MOISTURE HAS BEEN ABSORBED BY THE DEEP LAYER TROUGH TO THE N OF THE WAVE. THERE IS NOT MUCH EVIDENCE OF ANY LEFT OVER TROPICAL PORTION...SO JUST EXTRAPOLATED THE POSITION W SLIGHTLY. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 7N11W 5N23W 3N39W 3N51W. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 150 NM EITHER SIDE OF THE AXIS E OF 32W. DISCUSSION... GULF OF MEXICO... A WEAKENING SLOW MOVING FRONT EXTENDS ACROSS CENTRAL FLORIDA TOWARD THE YUCATAN CHANNEL ALONG 29N81W 27N84W 22N86W. LOW-LEVEL CONVERGENCE NEAR THIS BOUNDARY ALONG WITH A SOMEWHAT DIFFLUENT PATTERN ALOFT IS PRODUCING SCATTERED SHOWERS AND TSTMS ROUGHLY WITHIN 120 NM AS NOTED IN MOSAIC DOPPLER RADAR AND LIGHTNING DATA. THE TIGHTENED PRES GRADIENT BETWEEN THIS FRONT AND STRONG HIGH PRES OVER THE UPPER PLAINS IS PRODUCING STRONG NELY WINDS ACROSS THE CENTRAL AND E PORTIONS. THESE WINDS ARE EXPECTED TO INCREASE FURTHER WITH GALE CONDITIONS FORECAST FOR THE SW GULF IN ABOUT 30 HOURS. THE MAJORITY OF THE GULF...W OF 88W...IS UNDER STRONG SUBSIDENCE ALONG AND TO THE E OF AN UPPER TROUGH ALONG 97W/98W. A LOW-LEVEL SCATTERED STRATOCUMULUS DECK IS EVIDENT ON THE LAST FEW VIS IMAGES OF THE EVENING ACROSS THE CENTRAL AND W GULF SIGNALING THE COOLER STABLE AIRMASS IN PLACE. CARIBBEAN SEA... THE MAIN EVENT IN THE CARIBBEAN THIS EVENING IS THE LARGE AREA OF LOW PRES SITUATED S OF HISPANIOLA. FOR DETAILS SEE THE SPECIAL FEATURE SECTION ABOVE. ANOTHER LOW PRES TROUGH IS LOCATED IN THE NW CARIB ANALYZED FROM 21N86W TO 15N81W. VISIBLE IMAGERY SHOWS LOW-LEVEL TURNING CONCENTRATED NEAR 17N84W. IR IMAGERY AND LIGHTNING DATA REVEAL A FAIR AMOUNT OF SHOWERS AND TSTMS WITHIN 120 NM OF THE AXIS BUT NOT MUCH ORGANIZATION TO THIS ACTIVITY. ADDITIONAL DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR. A PATCH OF SCATTERED MODERATE CONVECTION IS LOCATED FARTHER S IN THE SW CARIB FROM 11N-14N BETWEEN 81W-83W. THE REMAINDER OF THE AREA...ROUGHLY N OF 16N BETWEEN 70W-79W...IS UNDER A WEDGE OF DRY MID AND UPPER LEVEL AIR IN A CONFLUENT ZONE TO THE S OF AN UPPER LOW OVER HAITI. ATLANTIC... STRONG HIGH PRESSURE DOMINATES THE WESTERN ATLANTIC ANCHORED BY A PAIR OF 1031 MB CENTERS IN THE NORTH ATLANTIC. THE TIGHT PRES GRADIENT BETWEEN THIS RIDGING AND A LARGE LOW PRES SYSTEM IN THE CARIB IS GENERATING AN AREA OF 20-30 KT NE TO E WINDS S OF 26N BETWEEN 63W AND 78W. THERE ARE LOW-LEVEL MOISTURE STREAMS STEERED BY THIS FLOW BUT THE LARGE AREA OF DRY AIR IN THE MID AND UPPER LEVELS IS PREVENTING THE FORMATION OF DEEP MOISTURE IN THIS REGION. AN UPPER LOW OVER HAITI IS SHEARING THE LOW PRES SYSTEM IN THE CARIB AND SPREADING DEBRIS MOISTURE INTO THE TROPICAL ATLC ROUGHLY S OF 22N W OF 58W. FARTHER E...A LARGE DEEP LAYER TROUGH DOMINATES THE CENTRAL ATLC WITH THE MAIN LOW CENTERED NEAR 32N48W...ANALYZED 1010 MB AT THE SFC. A COLD FRONT STRETCHES SW FROM THIS SYSTEM ALONG 32N47W 28N51W 29N63W. ANOTHER SFC LOW IS LOCATED TO THE SE OF THE MAIN ONE NEAR 28N45W ESTIMATED TO BE 1009 MB. THERE ARE ONLY ISOLATED SHOWERS AND TSTMS NEAR THE LOWS...WITH MORE SCATTERED ACTIVITY TO THE EAST GENERALLY N OF 25N BETWEEN 36W-42W IN AN UPPER DIFFLUENT AREA. THE E ATLC IS RATHER TRANQUIL UNDER THE INFLUENCE OF SFC RIDGING EXTENDING SWD FROM HIGH PRES E OF THE AZORES AND AN AMPLIFIED RIDGE/TROUGH PATTERN. THERE IS SOME MID-HIGH LEVEL CLOUDINESS EMBEDDED ON THE UPWARD SIDE OF THE RIDGE BUT MOST OF THIS DRIES OUT E OF 25W. $$ CANGIALOSI