000 AXNT20 KNHC 021731 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU AUG 02 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... A TROPICAL WAVE AND AN AREA OF LOW PRES IN THE E CARIB IS MOVING WWD NEAR 20 KT. A SATELLITE LOOP BEGINNING AT 00Z TODAY SHOWS CONVECTION SIGNIFICANTLY INCREASING IN BOTH COVERAGE AND MAGNITUDE...ALTHOUGH CLOUD TOPS HAVE WARMED A BIT OVER THE PAST HOUR OR TWO. CURRENTLY...SCATTERED TO NUMEROUS MODERATE CONVECTION IS FROM 13N-17N BETWEEN 64W-70W. WHILE CONVECTION IS IMPRESSIVE IT REMAINS CHALLENGING TO FIND THE LOW-LEVEL CENTER. THIS SYSTEM CONTINUES TO HAVE SOME POTENTIAL TO BECOME A TROPICAL CYCLONE DURING THE NEXT DAY OR SO. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS CURRENTLY ENROUTE TO INVESTIGATE THE SYSTEM. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 29W/30W S OF 18N MOVING W 15-20 KT. BESIDES FOR A FEW LOW TO MID CLOUD SWIRLS AND SCATTERED SHOWERS ALONG THE WAVE AXIS...THERE IS NOT MUCH ASSOCIATED ACTIVITY. STABLE DUSTY AIR SURROUNDS THE NRN EXTENSION OF THE WAVE AXIS. HIGH AMPLITUDE TROPICAL WAVE IS ALONG 44W MOVING W NEAR 15 KT OVER THE PAST 24 HOURS. THIS WAVE HAS A LARGE ENVELOPE OF LOW TO MID LEVEL CYCLONIC TURNING CLEARLY NOTED IN VISIBLE IMAGES WITH A WEAK LOW LEVEL CIRCULATION...ANALYZED 1012 MB...ALONG THE AXIS NEAR 11N. ALTHOUGH THE OVERALL STRUCTURE AND SIZE OF THIS WAVE IS RATHER IMPRESSIVE...CONVECTION IS CONFINED TO THE ITCZ WITH LITTLE SHOWER ACTIVITY NEAR THE WAVE AXIS ITSELF. TROPICAL WAVE IS ALONG 75W S OF 20N MOVING W NEAR 20 KT. THE WAVE PSN WAS ADJUSTED SLIGHTLY ON THIS MAP TO AGREE WITH A WWD MOVING SURGE OF MOISTURE EVIDENT ON THE UW-CIMSS TPW PRODUCT. REGARDLESS OF THE EXACT PSN...THERE IS NOT MUCH CURVATURE OR ORGANIZING TO THIS LOW-LEVEL FEATURE. A WEAKENING SMALL CLUSTER OF SHOWERS OVER ERN CUBA AND THE MORE TYPICAL FLARE UPS ALONG THE ITCZ AXIS IN THE SW CARIB ARE POSSIBLY ENHANCED BY THIS WAVE. TROPICAL WAVE IS ALONG 87W S OF 20N MOVING W NEAR 20 KT. LIKE THE WAVE TO ITS E...THE PSN WAS UPDATED ON THIS MAP IN RESPONSE TO A WEAK SURGE OF MOISTURE EVIDENT IN THE TPW FIELD. OTHERWISE CONVECTION NEAR IT IS MINIMAL ACROSS CENTRAL AMERICA AND THE CARIB WATERS. THERE IS A BURST IN THE EPAC WATERS...FOR MORE DETAILS REFER TO MIATWDEP. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 15N17W 11N32W 8N46W 10N55W 11N63W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF THE AXIS BETWEEN 42W-50W AND WITHIN 90 NM EITHER SIDE BETWEEN 50W-54W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE WITHIN 120 NM S OF THE AXIS E OF 30W. ...DISCUSSION... THE GULF OF MEXICO... MESSY WEATHER CONTINUES IN THE GULF OF MEXICO ASSOCIATED WITH A BROAD ELONGATED LOW PRES TROUGH. AS OF 15 UTC...THE BOUNDARY WAS ANALYZED FROM THE BIG BEND AREA OF FLORIDA TOWARD THE SE TEXAS COAST ALONG 29N83W 27N89W 29N96W. VISIBLE IMAGES AND SFC OBS SHOW BROAD ELONGATED CYCLONIC TURNING ALONG THIS TROUGH AXIS WITH SOME CONCENTRATION AND LOWER PRESSURES NEAR 28N86W...WHERE A 1011 MB LOW IS ANALYZED. IR IMAGES...LIGHTNING DATA AND AVAILABLE RADAR DATA INDICATE THAT SCATTERED SHOWERS AND TSTMS COVER THE REGION FROM 26N-30N...MOST ORGANIZED IN THE E GULF AND OVER CENTRAL FLORIDA. WHILE THIS LOW PRES SYSTEM IS POORLY ORGANIZED AT THE MOMENT...IT IS RESPONSIBLE FOR QUITE WINDY CONDITIONS...ESPECIALLY IN TSTMS...AS INDICATED BY SEVERAL SHIPS REPORTS IN THE 20-25 KT RANGE. THIS SHOWER ACTIVITY IS BEING ENHANCED BY A DIFFLUENT PATTERN ALOFT BETWEEN A SHORTWAVE TROUGH OVER THE SE STATES AND AN UPPER HIGH OVER THE SW U.S. THIS SYSTEM WILL CONTINUE TO BE MONITORED AS SLOW DEVELOPMENT IS POSSIBLE OVER THE NEXT DAY OR TWO. DEBRIS HIGH LEVEL CLOUDINESS COVERS MUCH OF THE REMAINDER OF THE GULF...EXCEPT FOR THE EXTREME SE PORTION AND S FLA...WHERE DRY AIR FROM THE BAHAMAS IS BEING ADVECTED IN. THE CARIBBEAN SEA... THE BIG STORY IN THE CARIB IS ASSOCIATED WITH THE SPECIAL FEATURE...SEE ABOVE. TWO OTHER TROPICAL WAVES ARE MOVING ACROSS THIS REGION GENERALLY HAVING LITTLE EFFECT ON THE WEATHER CONDITIONS ATTM. AN UPPER LOW IS SPINNING OVER THE SW CARIB NEAR 14N80W ENHANCING DRY STABLE AIR IN THE MID AND UPPER LEVELS FROM 13N-18N W OF 75W. PATCHES OF CLOUDS AND ISOLATED SHOWERS ARE ROTATING AROUND THE NRN SIDE OF THIS UPPER SYSTEM N OF 18N W OF 75W. CLUSTER OF SCATTERED MODERATE CONVECTION IS OVER THE SW PORTION S OF 11N W OF 78W TIED TO THE ITCZ. MAX TRADES ARE NEAR 25 KT NEAR THE COAST OF COLOMBIA...AS DEPICTED BY A QSCAT PASS NEAR 11Z. THE ATLANTIC OCEAN... WEAKENING SLOW MOVING FRONTAL BOUNDARY EXTENDS FROM NEAR BERMUDA TO NE FLORIDA. THIS BOUNDARY CONTINUES IN THE GULF...WHERE IT LACKS THERMAL GRADIENT. IR IMAGES AND LIGHTNING DATA INDICATE THAT SCATTERED SHOWERS AND TSTMS ARE WITHIN 60 NM OF THE FRONT. THE REMAINDER OF THE ATLC IS DOMINATED BY A 1029 MB HIGH NEAR 37N33W. THE COMBINATION OF THIS HIGH PRES AND A LARGE AREA OF STABLE AIR ALOFT IS PRODUCING WIDESPREAD FAIR WEATHER ACROSS THE MAJORITY OF THE ATLC BASIN TODAY. THE ONLY AREA OF CLOUDINESS WORTH NOTING...BESIDES THE TROPICAL WAVES DISCUSSED ABOVE...EXTENDS FROM 25N-30N BETWEEN 55W-59W. THIS MOISTURE IS ASSOCIATED WITH A LARGE UPPER LOW CENTERED NEAR 30N55W. OTHERWISE...THE TYPICAL STABLE SCATTERED LOW-LEVEL STRATOCUMULUS ARE THE MAIN SOURCE OF CLOUD COVER ACROSS THIS REGION. TRADES ARE MODERATE...EXCEPT NEAR THE ERN CARIB AND THE COAST OF AFRICA WHERE THE TIGHTENED PRES GRAD IS PRODUCING STRONGER WINDS. $$ CANGIALOSI