000 AXNT20 KNHC 201804 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT FRI JUL 20 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 1745 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS TITLED ALONG 18N44W 12N47W 5N48W MOVING W 15-20 KT. THIS WAVE CONTINUES TO EXHIBIT CLEAR CYCLONIC TURNING IN THE SURROUNDING SCATTERED TO BROKEN LOW TO MID FIELD. DEEP CONVECTION REMAINS ABSENT NEAR THIS WAVE THAT APPEARS TO HAVE PASSED BUOY 41041 AROUND 1100 UTC WHEN WINDS VEERED FROM ENE TO ESE. TROPICAL WAVE MOVING INTO THE CENTRAL CARIBBEAN IS ALONG 69W S OF 18N. SOME OF THE ENERGY ASSOCIATED WITH THIS WAVE APPEARS TO HAVE BROKEN OFF TO THE N OF PUERTO RICO...AND IS POISED TO TRACK NWWD AROUND THE PERIPHERY OF THE ATLC SFC RIDGE. THIS PORTION IS BEING ANALYZED AS A TROUGH N OF PUERTO RICO. THE CARIBBEAN PORTION IS TRACKING WWD 15-20 KT. ASSOCIATED SCATTERED SHOWERS/ISOLATED TSTMS ARE FROM 15N-19N BETWEEN 68W-75W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 9N14W 7N22W 13N42W 5N56W. SCATTERED MODERATE WITH EMBEDDED ISOLATED STRONG CONVECTION IS WITHIN 200 NM EITHER SIDE OF THE AXIS E OF 23W. THIS APPEARS TO BE ASSOCIATED WITH THE NEXT TROPICAL WAVE BASED ON ITS APPEARANCE IN SATELLITE IMAGERY AND UPSTREAM RAOB DATA. ISOLATED MODERATE IS WITHIN 120 NM EITHER SIDE OF THE AXIS BETWEEN 23W-34W. THE ITCZ IS QUIET ELSEWHERE. ...DISCUSSION... GULF OF MEXICO... ISOLATED TSTMS DOT MUCH OF THE ERN GULF E OF 90W THIS AFTERNOON...PRIMARILY ASSOCIATED WITH UPPER DIFFLUENCE BETWEEN AN UPPER TROUGH OVER THE NE PORTION AND RIDGING EXTENDING INTO THE WRN PORTION. FURTHER DIFFLUENCE ALOFT AROUND THE RIDGE...AND MOIST LOW LEVEL ONSHORE FLOW...IS ALSO SUPPORTING SCATTERED SHOWERS/ISOLATED TSTMS IN THE FAR NW PORTION OFF THE NRN TEXAS COAST...N OF 27N W OF 92W. SIMILAR TSTMS ARE WITHIN 60NM OF THE NE MEXICO COAST N OF 21N. AT THE SFC OVERALL WEAK RIDGING DOMINATES AND LOOKS TO PERSIST THROUGH SAT...EXCEPT FOR WEAK TROUGHING AHEAD OF A COLD FRONT IN THE NE PORTION. THIS PATTERN LOOKS TO YIELD WINDS OF MOSTLY 15 KT OR BELOW AND SEAS 4 FT OR LESS THROUGH THE WEEKEND. CARIBBEAN SEA... THE MOST ACTIVE WEATHER IS S OF HISPANIOLA ASSOCIATED WITH THE TROPICAL WAVE AS DESCRIBED ABOVE. A FEW SMALL CLUSTERS OF MODERATE CONVECTION AREA ALSO PRODUCING ISOLATED TSTMS IN THE SW CARIBBEAN S OF 11N...MOST LIKELY TIED TO THE ITCZ. AN UPPER LOW IS SPINNING JUST S OF WRN CUBA NEAR 19N82W. ASSOCIATED LIFT IS SUPPORTING ISOLATED TSTMS N OF 18N BETWEEN 80W-85W. AN UPPER HIGH DOMINATES THE ERN PORTION OF THE BASIN. LIGHT TO MODERATE TRADES DOMINATE AND EXPECTED TO PERSIST THROUGH THE WEEKEND...EXCEPT SLIGHTLY STRONGER NEAR THE COLOMBIAN COAST. ATLANTIC OCEAN... THE MAIN AREA OF FOCUS THIS AFTERNOON CONTINUES TO BE THE N PORTION OF THE CARIBBEAN TROPICAL WAVE THAT IS NOW BEING ANALYZED AS A SURFACE TROUGH ALONG 24N65W 19N68W. THIS...ALONG WITH UPPER DIFFLUENCE BETWEEN THE UPPER LOW NEAR 26N67W AND AN UPPER RIDGE EXTENDING NNE FROM THE LEEWARD ISLANDS...IS SUPPORTING THE DISORGANIZED CLOUDINESS AND SHOWERS EXTENDING NE FROM PUERTO RICO INTO THE ATLANTIC FOR SEVERAL HUNDRED MILES. UPPER-LEVEL WINDS ARE CURRENTLY NOT FAVORABLE FOR DEVELOPMENT...BUT COULD BECOME MORE FAVORABLE DURING THE NEXT COUPLE OF DAYS. ANOTHER CLUSTER OF MODERATE CONVECTION IS ROTATING AROUND THE NE PERIPHERY OF THE UPPER LOW N OF 28N BETWEEN 61W-66W. LIGHTNING DATA AGAIN SHOWS ISOLATED TSTMS IN THE FAR WRN ATLC...MOSTLY OVER THE GULF STREAM AND AHEAD OF A COLD FRONT MOVING TOWARDS THE SE US. ANOTHER BROAD UPPER LOW IS NEAR 27N50W...SUPPORTING ISOLATED TSTMS N OF 26N BETWEEN 49W-53W. THE REMAINDER OF THE DISCUSSION AREA IS WIDELY DOMINATED BY THE SRN PERIPHERY OF A STATIONARY 1033 MB HIGH NEAR 38N42W. THIS IS PRODUCING ABUNDANT FAIR WEATHER AND MODERATE TRADES E OF 45W. THE TRADES ARE LITTLE STRONGER WITHIN 400 NM OF THE AFRICAN COAST N OF 20N...WHERE THE GRADIENT REMAINS TIGHTER. A FAIRLY DENSE AREA OF AFRICAN DUST NOTED ON BOTH SIDES OF THE TROPICAL WAVE NEAR 47W...MOST CONCENTRATED E OF 30W. $$ WILLIS