000 AXNT20 KNHC 201804 TWDAT TROPICAL WEATHER DISCUSSION... NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN JUL 20 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... TROPICAL STORM CRISTOBAL AT 20/1800 UTC IS NEAR 34.6N 76.1W OR ABOUT 22 NM EAST OF CAPE LOOKOUT NORTH CAROLINA AND ABOUT 45 NM SOUTH-SOUTHWEST OF CAPE HATTERAS NORTH CAROLINA MOVING NE AT 6 KT. LATEST MINIMUM CENTRAL PRESSURE AS REPORTED BY AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT IS 1007 MB. DATA FROM THE RECONNAISSANCE AIRCRAFT INDICATE THAT THE MAXIMUM SUSTAINED WIND SPEED HAS DECREASED TO NEAR 35 KT WITH GUSTS TO 40 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. DRY AIR IN THE MID TO UPPER LEVELS HAS SEEMINGLY PREVENTED CRISTOBAL FROM DEVELOPING MUCH CONVECTION NEAR THE CENTER. HOWEVER...HEAVY SHOWERS/SCATTERED THUNDERSTORMS ARE OFFSHORE S OF THE CENTER FROM 30N-33N BETWEEN 75W-78W AND SCATTERED SHOWERS WITH POSSIBLE ISOLATED THUNDERSTORMS EXTENDING FROM 33N-37N BETWEEN 74W-78W WHICH IS BETWEEN ONSLOW BAY NORTH CAROLINA AND NORFOLK VIRGINA. NEWLY FORMED TROPICAL STORM DOLLY...PREVIOUSLY TROPICAL WAVE... IS IN THE NW CARIBBEAN AT 20/1800 UTC IS CENTERED NEAR 18.6N 84.5W OR ABOUT 220 NM EAST OF CHETUMAL MEXICO AND ABOUT 175 NM SOUTHEAST OF COZUMEL MEXICO MOVING NW AT 13 KT. MINIMUM CENTRAL PRESSURE RECENTLY REPORTED BY A NOAA RECONNAISSANCE AIRCRAFT WAS 1008 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 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. BROAD AREA OF SCATTERED SHOWERS/THUNDERSTORMS IS MOSTLY N OF CENTER COVERING THE AREA FROM 17N-23N BETWEEN 80W-85W INCLUDING W CUBA AND THE CAYMAN ISLANDS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS EXTEND INTO THE GULF OF MEXICO AND THE YUCATAN CHANNEL FROM 20N-25N BETWEEN 82W-90W INCLUDING THE N YUCATAN PENINSULA. TROPICAL STORM BERTHA IS CENTERED NEAR 51.3N 35.7W OR ABOUT 740 NM EAST-NORTHEAST OF CAPE RACE NEWFOUNDLAND MOVING NE AT 31 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB. ESTIMATED MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. THIS IS THE LAST ADVISORY ISSUED BY THE NATIONAL HURRICANE CENTER. SEE HIGH SEAS FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE...UNDER AWIPS HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 35W S OF 13N MOVING W NEAR 15 KT. LOW AMPLITUDE WAVE WITH A MID LEVEL ROTATION EMBEDDED WITHIN THE ITCZ NEAR 6N WITH NO ASSOCIATED CONVECTION. TROPICAL WAVE THAT WAS ALONG 58W WAS RELOCATED INTO THE E CARIBBEAN ALONG 62W/63W S OF 18N BASED ON VISIBLE SATELLITE IMAGERY AND UPPER AIR DATA. THE WAVE IS MOVING W NEAR 20 KT. ISOLATED/SCATTERED SHOWERS ARE S OF 16N BETWEEN 60W-66W INCLUDING THE WINDWARD ISLANDS. TROPICAL WAVE ALONG 95W S OF 21N MOVING W 15 KT. WAVE IS MOSTLY IN THE E PACIFIC REGION WITH NO SHOWER ACTIVITY IN THE BAY OF CAMPECHE. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 12N15W 10N24W 5N43W 8N60W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION HAS MOVED OFF THE COAST OF W AFRICA WITHIN 75 NM OF 18W FROM 9N-16N WITH CLUSTERS OF SIMILAR CONVECTION WITHIN 120/150 NM ALONG THE SW COAST OF AFRICA BETWEEN 9W-15W. SCATTERED MODERATE CONVECTION IS FROM 6N-10N BETWEEN 20W-31W WITH CLUSTERS OF SIMILAR CONVECTION FROM 4N-8N BETWEEN 39W-50W. ...DISCUSSION... GULF OF MEXICO... THE MAIN CONCERN FOR THE GULF THIS AFTERNOON IS T.S. DOLLY IN THE NW CARIBBEAN PROVIDING SHOWERS/THUNDERSTORMS TO THE SE GULF...SEE SPECIAL FEATURES ABOVE. WEAK UPPER HIGH IS IN THE NW GULF BUT IS BEING SQUEEZED NW BY AN APPROACHING UPPER LOW MOVING FROM THE NW CARIBBEAN OVER THE YUCATAN PENINSULA. THE ASSOCIATED UPPER RIDGE EXTENDS S INTO THE BAY OF CAMPECHE PROVIDING DRIER UPPER AIR AHEAD OF T.S. DOLLY. A SURFACE TROUGH WAS ANALYZED ALONG THE N GULF COAST AT 20/1500 UTC EXTENDING FROM SE GEORGIA JUST NW OF JACKSONVILLE FLORIDA INTO THE GULF NEAR PANAMA CITY ALONG 29N87W TO THE SE COAST OF LOUISIANA S OF NEW ORLEANS. THIS IS A TRAILING WEAKNESS OF T.S. CRISTOBAL IN THE SURFACE RIDGE ANCHORED BY A 1020 MB HIGH OVER THE LOWER MISSISSIPPI VALLEY AND IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF 27N BETWEEN 85W-94W. SIMILAR ACTIVITY IS WITHIN 90 NM ALONG THE COAST OF MEXICO FROM 20N-23N. OTHERWISE...THE REMAINDER OF THE GULF REMAINS CLEAR THIS AFTERNOON BUT EXPECT CONDITIONS TO DETERIORATE OVER A LARGER AREA OF THE SE GULF AS DOLLY APPROACHES THE YUCATAN PENINSULA. CARIBBEAN SEA... MAIN CONCERN FOR THE CARIBBEAN THIS AFTERNOON IS NEWLY FORMED TROPICAL STORM DOLLY IN THE NW CARIBBEAN...SEE SPECIAL FEATURES ABOVE. OTHERWISE...THE ITCZ AXIS EXTENDS ACROSS THE SW CARIBBEAN FROM COLOMBIA TO THE BORDER OF PANAMA/COSTA RICA GENERATING CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 90 NM ALONG THE COAT OF PANAMA...COSTA RICA...AN NICARAGUA S OF 13N. THE REMAINDER OF THE CARIBBEAN REMAINS REMARKABLY CLEAR THIS AFTERNOON. HOWEVER...MODERATE/STRONG EASTERLY TRADE WINDS PREVAIL ACROSS THE CARIBBEAN AND CAN USHER IN POSSIBLE ISOLATED SHOWERS. ATLANTIC OCEAN... T.S. CRISTOBAL IS ALONG THE OUTER BANKS OF NORTH CAROLINA THIS AFTERNOON...SEE SPECIAL FEATURES ABOVE. BROAD UPPER HIGH IS CENTERED OF W/CENTRAL CUBA DRAWING UPPER MOISTURE S OF T.S. CRISTOBAL OVER THE FAR W ATLC BUT WITH DRIER AIR AT THE SURFACE IS NOT PRODUCING ANY SIGNIFICANT SHOWER ACTIVITY. A VERY SMALL WEAK UPPER LOW IS IN THE W ATLC NEAR 27N64W WITH A 1016 MB SURFACE LOW NEAR 27N63W. A SURFACE TROUGH EXTENDS FROM 30N57W ALONG 29N61W THROUGH THE 1016 MB LOW THEN 25N65W TO 25N69W GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN 120 NM EITHER SIDE OF THE SURFACE TROUGH. A SECOND UPPER LOW IS IN THE CENTRAL ATLC NEAR 27N50W. THE REMAINDER OF CENTRAL AND E ATLC IS UPPER RIDGE AND A SURFACE RIDGE EXTENDS THROUGH THE AZORES SW TO 32N50W THEN W TO A 1022 MB HIGH NW OF BERMUDA NEAR 33N67W. STRONG SUBSIDENCE AND DRY STABLE AIR IS KEEPING MOST OF THE ATL FAIR WEATHER THIS AFTERNOON. $$ WALLACE