000 AXNT20 KNHC 221802 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT MON SEP 22 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... A BROAD AREA OF LOW PRESSURE CONTINUES BRINGING HEAVY RAINS TO PUERTO RICO AND ADJACENT WATERS. CURRENTLY...THIS SYSTEM LACKS A WELL-DEFINED CIRCULATION CENTER AT THE SURFACE. A 1008 MB SURFACE LOW HAS BEEN ANALYZED OVER THE E TIP OF THE DOMINICAN REPUBLIC...NEAR 19N68W...BASED ON REFLECTIVITY TRENDS ON SAN JUAN WEATHER SERVICE DOPPLER RADAR. A LARGE CLUSTER OF SHOWERS AND THUNDERSTORMS CONTINUES IMPACTING AREAS S AND E OF THE ANALYZED LOW...FROM 14N-19N BETWEEN 65W-69W. THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE IN NORTHWESTERLY FLOW ALOFT. HEAVY RAINFALL...LIFE-THREATENING FLASH FLOODS...AND MUDSLIDES ARE EXPECTED TO CONTINUE IMPACTING PUERTO RICO AND THE U.S. VIRGIN ISLANDS INTO TUESDAY. UPPER-LEVEL WINDS ARE EXPECTED TO BECOME A LITTLE MORE FAVORABLE FOR DEVELOPMENT DURING THE NEXT DAY OR SO...AND THIS SYSTEM STILL HAS THE POTENTIAL TO BECOME A TROPICAL DEPRESSION AS IT MOVES SLOWLY TO THE NORTH OR NORTH-NORTHWEST. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 29W/30W S OF 16N MOVING W 10-15 KT. WAVE IS EMBEDDED WITHIN A BROAD AREA OF DEEP LAYER MOISTURE AS INDICATED BY MIMIC TOTAL PRECIPITABLE WATER ANIMATION. RECENT SATELLITE TRENDS DEPICT WEAK...BROAD LOW/MID-LEVEL CIRCULATION IN THE VICINITY OF THE WAVE AXIS N OF 12N....WHERE SCATTERED MODERATE CONVECTION IS DEVELOPING 90 NM EITHER SIDE OF THE WAVE AXIS. LOW AMPLITUDE TROPICAL WAVE IS ALONG 45W S OF 14N MOVING WEST 10-15 KT. THIS WAVE HAS BEEN ANALYZED FURTHER SOUTH OF PREVIOUS ANALYSES...WHERE TOTAL PRECIPITABLE WATER IS SUBSTANTIALLY LARGER. CLUSTERS OF MODERATE/ISOLATED STRONG CONVECTION HAVE DEVELOPED FROM 6N-10N BETWEEN 40W-49W...NEAR THE INTERSECTION OF THE WAVE AND THE ITCZ. TROPICAL WAVE IS ALONG 63W S OF 20N MOVING W 10 KT. THIS WAVE IS MOVING INTO THE AREA OF THE BROAD LOW PRESSURE DESCRIBED IN THE SPECIAL FEATURES SECTION. SURFACE WINDS AROUND THE LESSER ANTILLES HAVE VEERED UPON WAVE PASSAGE. CONVECTION WITH THIS WAVE IS GENERALLY BEING SUPPRESSED BY SUBSIDENCE ON THE E PERIPHERY OF CONVECTION OVER THE E CARIBBEAN. HOWEVER... ISOLATED SHOWERS ARE OCCURRING 150 NM E OF THE WAVE AXIS. TROPICAL WAVE IS ALONG 78W/79W S OF 16N MOVING W 10-15 KT. THIS WAVE HAS BEEN RELOCATED TO THE E FROM ITS 22/06Z MON POSITION ALONG 71W S OF 18N. THE RELOCATION OF THIS WAVE IS BASED ON AN INVERTED-V PATTERN IN THE CLOUD ELEMENTS ALONG THE WAVE AXIS S OF 12N...AS WELL AS TEMPORAL CONTINUITY OF WAVE TRACKING. WEAK COUNTERCLOCKWISE CURVATURE IS NOTED IN THE LOW LEVEL FLOW FROM A RECENT QUIKSCAT PASS. ISOLATED SHOWERS ARE OCCURRING 60 NM EITHER SIDE OF THE WAVE AXIS. TROPICAL WAVE IS ALONG 90W S OF 21N MOVING W NEAR 10-15 KT. THIS WAVE IS INLAND OVER THE YUCATAN PENINSULA AND INTO THE E PACIFIC REGION WITH SCATTERED MODERATE CONVECTION 150 NM EITHER SIDE OF THE WAVE AXIS FROM 8N-15N...WITH ISOLATED MODERATE CONVECTION 60 NM EITHER SIDE OF THE WAVE AXIS FROM 15N-21N. ...THE ITCZ... ITCZ AXIS IS ANALYZED ALONG 8N13W 10N31W 9N41W 9N60W 10N82W. ISOLATED MODERATE CONVECTION IS FROM 7N-12N BETWEEN 34W-40W. SCATTERED MODERATE CONVECTION FURTHER W OF THIS AREA...FROM 6N-10N BETWEEN 40W-49W...IS BEING ENHANCED BY MOIST LOW LEVEL CONVERGENCE TO THE E OF THE TROPICAL WAVE ALONG 45W. ISOLATED MODERATE CONVECTION IS AFFECTING THE AREA 60 NM NORTH AND SOUTH OF A LINE FROM 11N81W TO 11N84W. ...DISCUSSION... GULF OF MEXICO... A SURFACE TROUGH EXTENDS FROM NEAR BROWNSVILLE TEXAS TO THE BAY OF CAMPECHE...FROM NEAR 26N97W TO 19N95W...WITH SCATTERED SHOWERS AND THUNDERSTORMS AFFECTING THE W GULF. THIS ACTIVITY IS BEING ENHANCED BY DIFFLUENCE IN NORTHWESTERLY FLOW ALOFT EAST OF AN UPPER HIGH NEAR 22N97W. AN UPPER RIDGE EXTENDS EASTWARD FROM THIS HIGH INTO THE S GULF. WEAK UPPER LEVEL DIFFLUENT FLOW NORTH OF THE RIDGE AXIS COMBINED WITH COPIOUS AMOUNTS OF MOISTURE ARE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORM DEVELOPMENT INTO THE CENTRAL GULF. OVER THE N GULF...STRONG FLOW IN THE BASE OF BROAD UPPER LEVEL TROUGH IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS OVER THE NE GULF FROM 28N-30N BETWEEN 83W-87W. GENERALLY FAIR WEATHER IS OCCURRING IN THE SE GULF...WHERE STABLE CONDITIONS BENEATH THE UPPER RIDGE PREDOMINATE. CARIBBEAN SEA... THE MAIN CONCERN FOR THE NEXT FEW DAYS IS THE AREA OF LOW PRESSURE DESCRIBED IN THE SPECIAL FEATURES SECTION. AN UPPER TROUGH EXTENDS FROM CENTRAL CUBA TO BELIZE. THIS UPPER TROUGH IS BETWEEN THE UPPER RIDGE OVER THE GULF...AND AN UPPER HIGH OVER THE CARIBBEAN CENTERED NEAR 15N74W. STABLE CONDITIONS BENEATH THIS UPPER HIGH ARE SUPPORTING MAINLY FAIR WEATHER CONDITIONS AND ISOLATED SHOWERS OVER THE CENTRAL CARIBBEAN. SCATTERED MODERATE CONVECTION IS AFFECTING THE WESTERN CARIBBEAN OFF THE E COASTS OF YUCATAN...BELIZE...AND HONDURAS FROM 15N-21N BETWEEN 81W-88W. UPPER LEVEL DIFFLUENCE W OF AN UPPER HIGH OVER THE LESSER ANTILLES NEAR 15N61W IS ENHANCING CONVECTION OVER THE E CARIBBEAN...DISCUSSED IN THE SPECIAL FEATURES SECTION. ATLANTIC OCEAN... A SURFACE TROUGH EXTENDS FROM 31N78W TO THE E FLORIDA COAST NEAR 28N81W. SURFACE CONVERGENCE WITH THIS TROUGH IS PROMOTING SCATTERED SHOWERS OVER THE WESTERN ATLANTIC N OF 29N BETWEEN 76W AND THE FLORIDA W COAST. MOIST SOUTHWESTERLY FLOW ALOFT AROUND A BROAD TROUGH OVER THE E CONUS IS SUPPORTING THIS ACTIVITY. OTHERWISE...A 1025 MB SUBTROPICAL HIGH NEAR 33N56W IS BENEATH AN UPPER HIGH. STABLE CONDITIONS NEAR THESE FEATURES ARE RESULTING IN FAIR WEATHER OVER MUCH OF THE CENTRAL ATLANTIC...THOUGH THERE ARE A FEW SHOWERS FROM 28N-32N BETWEEN 63W-66W NEAR AN UPPER TROUGH. MOISTURE E OF AN UPPER LOW NEAR 24N48W IS RESULTING IN AN AREA OF MID/HIGH-LEVEL CLOUDINESS FROM 22N-27N BETWEEN 39W-49W. TO THE E OF THIS CLOUDINESS RESIDES A 1020 MB HIGH NEAR 27N30W...WHICH IS FORECAST TO DISSIPATE OVER THE NEXT 24 HOURS AS MOIST SOUTHWESTERLY FLOW ALOFT REPLACES THE UPPER RIDGE CURRENTLY OVER THE SURFACE HIGH. OVER THE TROPICAL ATLANTIC...THE CLOCKWISE CIRCULATION AROUND AN UPPER HIGH NEAR 15N61W IS SPREADING MID/HIGH LEVEL CLOUDINESS NEARLY 300 NM NORTH OF PUERTO RICO AND HISPANIOLA FROM THE CONVECTION MENTIONED IN THE SPECIAL FEATURES SECTION. AN UPPER LEVEL RIDGE EXTENDS WESTWARD INTO THE CENTRAL TROPICAL ATLANTIC FROM AN UPPER HIGH NEAR 16N27W...BRINGING FAIR WEATHER TO MUCH OF THE TROPICAL ATLANTIC. $$ COHEN