000 AXNT20 KNHC 201033 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0945 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS TITLED FROM 21N40W 15N44W 7N46W MOVING W 15-20 KT. BROAD WAVE LOW LEVEL INVERTED-V CURVATURE COVERING THE AREA FROM 38N-50N. NO ASSOCIATED SHOWERS/CONVECTION. TROPICAL WAVE IN THE E CARIBBEAN HAS BEGUN TO SPLIT WITH THE N PORTION MOVING SLOWER NW THAN THE S PORTION MOVING W. WAVE IS ALONG 67W/68W S OF 17N MOVING W 15 KT. THE N PORTION OF THIS WAVE HAS SOME POTENTIAL FOR FURTHER DEVELOPMENT. SEE BELOW. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE FROM 14N-18N BETWEEN 66W-71W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 9N12W 6N21W 13N46W 11N61W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 150/200 NM OF THE AXIS E OF 18W TO JUST INLAND OVER SIERRA LEONE AND GUINEA AFRICA. SIMILAR CONVECTION IS WITHIN A 75 NM RADIUS OF 9N20W. ...DISCUSSION... GULF OF MEXICO... UPPER LEVEL HIGH IS INLAND OVER NE MEXICO WITH THE UPPER RIDGE COVERING THE GULF W OF 87W ENHANCING LOW LEVEL SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 120 NM ALONG THE COAST OF TEXAS AND LOUISIANA. SHORTWAVE UPPER TROUGH EXTENDS FROM JUST OFF THE E COAST OF THE CAROLINAS OVER NE FLORIDA INTO THE FAR NE GULF BRINGING SHOWER ACTIVITY TO THE W ATLC. THE CUT-OFF UPPER LOW THAT IS JUST W OF THE CAYMAN ISLANDS COVERS THE GULF S OF 25N E OF 87W INTO THE W ATLC GENERATING ISOLATED SHOWERS/ THUNDERSTORMS S OF 26N E OF 84W. OTHERWISE A WEAK SURFACE RIDGE REMAINS ACROSS THE GULF FROM THE W ATLC WITH A 1018 MB HIGH OVER THE NE GULF NEAR 28N86W. CARIBBEAN SEA... AN ELONGATED CUT-OFF UPPER LOW REMAINS CENTERED JUST E OF THE CAYMAN ISLANDS NEAR 20N83W COVERING THE AREA N OF 17N FROM 76W TO THE YUCATAN PENINSULA GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM N OF 17N FROM 75W-84W WITH THE BULK OF THE ACTIVITY ALONG THE COAST OF CUBA FROM 80W-83W. BROAD UPPER HIGH IS CENTERED OVER THE FAR NE CARIBBEAN NEAR 17N64W COVERING THE E CARIBBEAN E OF 75W AND EXTENDS INTO THE W TROPICAL ATLC AND CENTRAL ATLC. THE ITCZ AXIS IN THE E PACIFIC REGION EXTENDS ACROSS PANAMA AND COSTA RICA GENERATING SCATTERED MODERATE/ ISOLATED STRONG CONVECTION S OF 10N FROM COLOMBIA TO COSTA RICA. MODERATE/STRONG EASTERLY TRADE WINDS CONTINUE ACROSS THE CARIBBEAN S OF 17N. ATLANTIC OCEAN... THE MAIN AREA OF FOCUS THIS MORNING THAT WAS THE N PORTION OF THE CARIBBEAN TROPICAL WAVE AND IS NOW A SURFACE TROUGH THAT EXTENDS FROM THE MONA PASSAGE TO NEAR 25N63W. THIS BROAD AREA OF LOW LEVEL CYCLONIC TURNING IS PRODUCING HEAVY RAINS WITH EMBEDDED THUNDERSTORMS E OF THE TROUGH AXIS FROM 16N-23N BETWEEN 69W-65W INCLUDING THE LEEWARD AND VIRGIN ISLANDS. THE RAINS HAVE NOT BEGUN IN ERNEST OVER PUERTO RICO AS OF YET BUT WILL BE MOVING OVER THE ISLAND LATER TODAY. OTHERWISE...SHORTWAVE UPPER TROUGH EXTENDS FROM JUST OFF THE E COAST OF THE CAROLINAS ACROSS NE FLORIDA AND EXTENDS OVER THE W ATLC N OF 27N W OF 76W GENERATING SCATTERED SHOWERS/THUNDERSTORMS WITHIN 200 NM ALONG THE E US COAST N OF 30N. CUT-OFF UPPER LOW JUST E OF THE CAYMAN ISLANDS COVERS THE SW ATLC S OF 25N W OF 76W BUT IS ONLY PRODUCING WIDELY ISOLATED SHOWERS BETWEEN CUBA AND THE BAHAMA ISLANDS. AN UPPER LOW REMAINS IN THE NW ATLC NEAR 26N67W COVERING THE AREA N OF 23N FROM 63W-73W WITH A WEAKENING SURFACE TROUGH EXTENDING FROM 31N64W TO 26N66W. THE UPPER LOW IS BEING OVERRUN BY THE UPPER RIDGE TO THE S AND IS DRAWING UPPER LEVEL MOISTURE N AWAY FROM THE TROUGH THAT EXTENDS FROM THE MONA PASSAGE TO 24N63W. THE UPPER HIGH IN THE NE CARIBBEAN EXTENDS A RIDGE AXIS NE ACROSS THE LEEWARD/VIRGIN ISLANDS TO NEAR 26N59W ENHANCING THE HEAVY RAINS AND THUNDERSTORMS ASSOCIATED WITH THE SURFACE TROUGH MENTIONED ABOVE. A CUT-OFF UPPER LOW IS CENTERED IN THE CENTRAL ATLC NEAR 29N50W COVERING THE AREA N OF 16N FROM 40W-56W WITH A VERY NARROW UPPER RIDGE BETWEEN THIS UPPER LOW AND THE UPPER LOW CENTERED NEAR 26N67W ENHANCING SCATTERED SHOWERS FROM 25N-31N BETWEEN 46W-66W. UPPER RIDGE EXTENDS OFF THE COAST OF AFRICA OVER THE E ATLC E OF 37W. THE FIRST VISIBLE SATELLITE IMAGES OF THE DAY CONTINUE TO SHOW A LARGE AREA OF AFRICAN DUST ALTHOUGH IT APPEARS LESS DENSE THAN YESTERDAY. THE REMAINDER OF THE ATLC CONTINUES TO BE DOMINATED BY A SURFACE RIDGE ANCHORED BY A 1032 MB HIGH CENTERED N OF THE REGION TO OVER THE N GULF OF MEXICO. $$ WALLACE