000 AXNT20 KNHC 230014 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED AUG 22 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2345 UTC. ...SPECIAL FEATURE... TROPICAL STORM DEAN CONTINUES TO PUSH FURTHER INLAND OVER MEXICO AND HAS WEAKENED QUITE RAPIDLY OVER THE HIGH TERRAIN OF MEXICO. AS OF 0000 UTC DEAN WAS CENTERED NEAR 20.5N 99.0W...OR ABOUT 75 MILES NORTH OF MEXICO CITY MEXICO...MOVING W AT 17 MPH. MAXIMUM SUSTAINED WIND SPEEDS HAVE DECREASED TO 45 MPH WITH HIGHER GUSTS OVER THE ELEVATED TERRAIN OF THE SIERRA MADRE. ESTIMATED MINIMUM CENTRAL PRESSURE IS 996 MB. PLEASE SEE THE LATEST NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE LATEST PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS. DEAN RETAINS A WELL ORGANIZED CONVECTIVE CLOUD PATTERN AT THE MID AND UPPER LEVELS DESPITE THE TREK OVER THE HIGH TERRAIN...HOWEVER AT THE LOW LEVELS SURFACE OBSERVATIONS INDICATE THAT THE SYSTEM HAS BEEN ESSENTIALLY SHREDDED OVER THE MEXICAN TERRAIN. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OCCURRING OVER CENTRAL MEXICO WITH OVERCAST MID AND HIGH LEVEL CLOUD DEBRIS EXTENDING OVER THE WRN BAY OF CAMPECHE AND GULF OF MEXICO. CONTINUED WEAKENING IS EXPECTED UNTIL DEAN DISSIPATES OVER THE MOUNTAINS OF CENTRAL MEXICO OVERNIGHT. DEAN IS EXPECTED TO PRODUCE STORM TOTAL RAINFALL OF 5 TO 10 INCHES OVER PARTS OF SOUTHERN AND CENTRAL MEXICO...WITH MAXIMUM AMOUNTS OF UP TO 20 INCHES. THESE RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUDSLIDES. ...TROPICAL WAVES... TROPICAL WAVE IS TILTED ALONG 22N60W TO THE SOUTH AMERICAN COAST AT 8N59W MOVING W 15 KT. SHORTWAVE INFRARED SATELLITE IMAGERY SHOWS AN ELONGATED AND NARROW ZONE OF LOW LEVEL CYCLONIC TURNING IN ASSOCIATION WITH THIS WAVE JUST E OF THE LESSER ANTILLES. IN ADDITION...THE WAVE SHOWS UP WELL IN THE UW-CIMSS TPW PRODUCT AS A SECONDARY SURGE OF MOISTURE BEHIND THE LARGER WAVE TO ITS W. DEEP CONVECTION IS MINIMAL AND DISORGANIZED WITH THIS WAVE... THOUGH A FEW ISOLATED TSTMS ARE NEAR THE SRN PORTION OF THE AXIS S OF 14N OVER THE SRN WINDWARD ISLANDS GENERALLY BETWEEN 60W-63W. A VERY HIGH AMPLITUDE TROPICAL WAVE IS ALONG 75W/76W S OF 29N MOVING W AT A BRISK 15-20 KT. SATELLITE IMAGERY STILL SHOWS THAT THE FOCUS OF THE LOW LEVEL TURNING IS JUST E OF THE CENTRAL BAHAMAS WITH A WELL DEFINED LOW LEVEL CENTER NOTED NEAR 25N76W. BAHAMAS METAR DATA TO THE S OF THIS TURNING STILL INDICATE LIGHT NE WINDS...THUS THE FEATURE DOES NOT APPEARS TO BE CLOSED AT THE SURFACE AT THIS TIME. THE ASSOCIATED SCATTERED SHOWERS AND ISOLATED TSTMS ARE RATHER SPARSE AND NOT ORGANIZED AND NOW EXTEND NWD FROM ERN CUBA ACROSS THE NW BAHAMAS. THE WAVE IS EXPECTED TO BRING SHOWERS AND THUNDERSTORMS TO THE FLORIDA PENINSULA OVER THE NEXT DAY OR SO. HOWEVER...UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR TROPICAL CYCLONE FORMATION AS THE WAVE IS SITUATED OVER THE NORTHERN EXTENT OF A AN UPPER LEVEL LOW OVER THE NW CARIBBEAN. CONVECTION NOTED EARLIER WITH THE CARIBBEAN PORTION OF THE WAVE BETWEEN 73W-77W HAS ALL BUT DISSIPATED. THIS SRN BRANCH OF THE WAVE IS EXPECTED TO BRING MOISTURE ADDITIONAL SHOWERS TO CENTRAL AMERICA AND THE YUCATAN OVER THE SECOND PART OF THE WEEK. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 12N16W 9N30W 10N42W 9N58W. THE ITCZ REMAINS HIGHLY ZONAL FOR LATE AUGUST WITH SCATTERED MODERATE ISOLATED CONVECTION WITHIN 120 NM OF THE AXIS BETWEEN 22W AND 36W. UW CIMSS SAHARAN AIR LAYER ANALYSES AND BACKWARD EXTRAPOLATION OF A WAVE PASSAGE OFF THE AFRICAN COAST ON AUG 19 INDICATE A LOW AMPLITUDE TROPICAL WAVE ALONG 40W. THIS WAVE WILL BE ADDED ON THE 0000 UTC SFC ANALYSIS. DISCUSSION... GULF OF MEXICO... THE MAIN FOCUS THIS EVENING REMAINS WEAKENING TROPICAL STORM DEAN THAT DESPITE MOVING FURTHER INLAND OVER MEXICO NEAR THE TOWN OF TECOLUTLA...SEE SPECIAL FEATURES ABOVE. DEAN IS BEING STEERED WWD BY A DEEP LAYER RIDGE TO ITS N/NE. TROPICAL MOISTURE FROM DEAN IS ROUNDING THIS RIDGE AND MOVING THROUGH TEXAS. DRY/STABLE AIR IS OVER THE ERN GULF KEEPING WEATHER MOSTLY FAIR...THOUGH MOISTURE/SHOWERS EXPECTED TO INCREASE THROUGH THU IN THE SE PORTION WITH THE APPROACHING TROPICAL WAVE AND MID TO UPPER LOW. SFC RIDGING WILL REMAIN QUASI STATIONARY OVER THE N GULF OVER THE NEXT FEW DAYS. CARIBBEAN SEA... THE MOST SIGNIFICANT AREA OF WEATHER IN THE CARIBBEAN IS IN THE SW PORTION...WITH SCATTERED SHOWERS AND TSTMS S OF 15N BETWEEN 73 AND 78W. THE CONVECTION IN THIS VICINITY IS IN PART DUE TO THE TROPICAL WAVE ALONG 75W/76W AS DESCRIBED ABOVE...BUT IS ALSO BEING SUPPORTED BY DIFFLUENT FLOW ALOFT. MOISTURE WITH THIS WAVE...AND THE WAVE NEARING THE WINDWARD ISLANDS...WILL PUSH W THROUGH THE BASIN OVER THE NEXT COUPLE OF DAYS. ELSEWHERE AT THE SFC LIGHT TO MODERATE TRADES ARE IN PLACE AND GENERALLY EXPECTED TO PERSIST THROUGH THU. THE UPPER PATTERN IS DOMINATED BY THE LARGE AND ELONGATED UPPER LOW JUST S OF CUBA...AND THE SRN PERIPHERY OF AN UPPER RIDGE OVER THE ERN PORTION. LIFT WITH THE UPPER LOW IS ALSO SUPPORTING SCATTERED SHOWERS/ISOLATED TSTMS OVER THE NW CARIBBEAN N OF 15N BETWEEN 79W-84W. ATLANTIC OCEAN... SHOWERS AND TSTMS ARE MOVING THROUGH THE WRN ATLC WITH THE TROPICAL WAVE ALONG 75W/76W AS DESCRIBED ABOVE. TROUGHING IS VERTICALLY STACKED IN THIS VICINITY...EXTENDING N FROM AN UPPER LOW JUST S OF CUBA. AN UPPER HIGH IS NEAR 30N60W THAT HAS RIDGING EXTENDING S TO THE ERN CARIBBEAN. THIS IS SUPPORTING A FEW ISOLATED TSTMS BETWEEN 65W-70W. BENIGN UPPER LOWS ARE NOTED NEAR 23N52W AND 32N36W...WHILE THE REMAINDER OF THE FAR ERN ATLC AREA IS DOMINATED BY TYPICAL UPPER RIDGING. ELSEWHERE AT THE SFC A 1021 MB HIGH IS NEAR 30N56W...EXPECTED TO SLIDE SW IN ADVANCE OF THE FRONTAL SYSTEM N OF THE AREA. LIGHT TO MODERATE TRADE WINDS AND FAIR WEATHER AROUND THIS RIDGING DOMINATE MUCH OF THE AREA N OF 13N E OF 50W. $$ COBB