000 AXNT20 KNHC 211803 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT MON JUL 21 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 1645 UTC. ...SPECIAL FEATURES... TROPICAL STORM DOLLY AT 21/1800 IS CENTERED NEAR 22.8N 90.4W OR ABOUT415 NM EAST-SOUTHEAST OF THE COAST OF THE LOWER RIO GRANDE VALLEY OF SOUTH TEXAS AND NORTHEASTERN MEXICO MOVING WNW AT 16 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT4/ WTNT34 KNHC FOR MORE DETAILS. VISIBLE SATELLITE IMAGERY CLEARLY SHOWS THE CLOSED CENTER OF CIRCULATION WITH THE DEEP CONVECTION MOSTLY OFFSHORE FROM THE YUCATAN CHANNEL OVER THE S/CENTRAL GULF. SCATTERED STRONG CONVECTION IS WITHIN 250 NM OF THE CENTER IN THE NW QUADRANT WITH SCATTERED MODERATE/STRONG CONVECTION WITHIN 150 NM OF THE CENTER IN THE NW QUADRANT. TROPICAL STORM CRISTOBAL AT 21/1500 UTC IS CENTERED NEAR 36.6N 72.6W OR ABOUT ABOUT 165 NM EAST-NORTHEAST OF CAPE HATTERAS NORTH CAROLINA AND ABOUT 630 NM SOUTHWEST OF HALIFAX NOVA SCOTIA MOVING NE AT 11 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 KT. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT3/ WTNT33 KNHC FOR MORE DETAILS. SOME FURTHER INTENSIFICATION IS POSSIBLE WHILE THE CENTER MOVES ACROSS THE GULF STREAM AND THE SHEAR REMAINS LOW DURING THE NEXT 24 HR OR SO. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 150 NM OF THE CENTER IN SE SEMICIRCLE. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 45W/46W S OF 13N MOVING W NEAR 20 KT. LOW AMPLITUDE WAVE A WEAK MID LEVEL ROTATION EMBEDDED WITHIN THE ITCZ NEAR 8N. THIS WAVE IS EMBEDDED WITHIN AN AREA OF DRY STABLE AIR THUS NO ASSOCIATED SHOWERS/CONVECTION. TROPICAL WAVE IN THE E CARIBBEAN IS ALONG 70W S OF 19N MOVING W 15-20 KT. WEAK WAVE IS EMBEDDED WITHIN DRY STABLE AIR. THUS SATELLITE SIGNATURE IS NOT DISCERNIBLE. ISOLATED SHOWERS ARE FROM OVER THE ABC ISLANDS TO THE N COAST OF VENEZUELA BETWEEN 66W-71W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 11N14W 8N26W 9N40W 6N55W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM EITHER SIDE OF THE ITCZ E OF 18W TO THE COAST OF SW AFRICA. CLUSTERS OF SIMILAR CONVECTION ARE FROM 11N-14N E OF 20W TO INLAND OVER W AFRICA. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE WITHIN 150 NM N OF THE ITCZ FROM 22W-29W AND WITHIN 200 NM S OF THE ITCZ FROM 19W-35W. ...DISCUSSION... GULF OF MEXICO... THE MAIN CONCERN FOR THE GULF IS T.S. DOLLY AS IT MOVES AWAY FROM THE N YUCATAN COAST...SEE SPECIAL FEATURES ABOVE. BROAD UPPER LEVEL OUTFLOW COVERS MOST OF THE GULF S OF 28N. WEAK UPPER TROUGH EXTENDS FROM THE GEORGIA COAST TO ALONG THE E COAST OF FLORIDA BRINGING DRIER AIR TO THE FLORIDA PENINSULA. AT THE SURFACE A WEAK RIDGE OF HIGH PRESSURE COVERS THE SE U.S. WITH A PAIR OF 1018 MB HIGHS IN THE NE AND NW GULF CENTERED NEAR 21N84W AND 29N92W. A SMALL UPPER LOW IS IN THE W BAY OF CAMPECHE ALONG THE MEXICAN COAST GENERATING ISOLATED SHOWERS/THUNDERSTORMS OF 21N W OF 94W. AN AREA OF ISOLATED SHOWERS/THUNDERSTORMS ARE FEEDING INTO T.S. DOLLY FROM OFF THE N GULF COAST WITHIN 90 NM OF LINE FROM 29N92W TO 25N94W. OTHERWISE THE MEXICAN COAST N OF TUXPAN ALONG THE N GULF AND OVER THE FLORIDA PENINSULA REMAIN CLEAR THIS AFTERNOON. CARIBBEAN SEA... T.S. DOLLY IS STILL PRODUCING AN AREA OF HEAVY SHOWERS/SCATTERED THUNDERSTORMS OVER THE FAR NW CARIBBEAN N OF 20N W OF 83W ACROSS THE FAR W TIP OF CUBA AND OVER THE NE TIP OF THE YUCATAN PENINSULA. SEE SPECIAL FEATURES ABOVE. CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE OVER THE REMAINDER OF THE NW CARIBBEAN N OF 14N W OF 80W. BROAD UPPER LEVEL OUTFLOW COVERS THE W CARIBBEAN W OF 78W. AN UPPER TROUGH COVERS THE REMAINDER OF THE CARIBBEAN EXTENDING FROM AN UPPER LOW OVER PUERTO RICO SW TO COLOMBIA. THIS IS DRAWING DRIER UPPER AIR FROM THE W ATLC OVER THE E CARIBBEAN AND WITH LITTLE MOISTURE AT THE SURFACE IS KEEPING THE CARIBBEAN E OF 78W CLEAR THIS AFTERNOON. UPPER LEVEL N TO NE FLOW CONVERGING WITH LOW LEVEL EASTERLY TRADE WINDS ARE GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS IN THE SW CARIBBEAN WITHIN 120 NM ALONG THE COAST OF PANAMA...COSTA RICA...AND NICARAGUA. ATLANTIC OCEAN... T.S. CRISTOBAL IS MOVING NE AWAY FROM NORTH CAROLINA WITH SKIES CLEARING ALONG THE COAST. SEE SPECIAL FEATURES ABOVE. WEAK UPPER TROUGH EXTENDS FROM THE GEORGIA COAST TO ALONG THE E COAST OF FLORIDA BRINGING DRIER AIR TO THE FLORIDA PENINSULA AND THE FAR W ATLC. A SECOND WEAK UPPER LOW IS JUST TO E NEAR 28N72W AND IS DRAWING UPPER LEVEL MOISTURE FROM T.S. CRISTOBAL S TO OVER THE BAHAMAS BETWEEN 73W-77W BUT IS NOT PRODUCING ANY SHOWER ACTIVITY. A COMPLEX UPPER LOW/TROUGH COVERS THE REMAINDER AND INTO THE CENTRAL ATLC BETWEEN 52W-67W WITH A SURFACE TROUGH EXTENDING FROM 33N57W THROUGH A PAIR OF 1012 MB LOWS CENTERED NEAR 30N64W AND 27N67W CONTINUING TO 24N71W GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN 120 NM EITHER SIDE OF THE SURFACE TROUGH. AN UPPER RIDGE IS OVER THE REMAINDER OF THE CENTRAL ATLC INTO THE E ATLC ANCHORED NEAR 25N37W AND PROVIDING UPPER LEVEL DIFFLUENCE TO THE E OF THE SURFACE TROUGH GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 23N-28N BETWEEN 55W-60W. LARGE SURFACE RIDGE DOMINATES THE ATLC E OF 60W ANCHORED BY A 1027 MB HIGH JUST N OF THE REGION NEAR 25N40W. $$ WALLACE