000 AXNT20 KNHC 212355 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT FRI SEP 21 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 2315 UTC. ...SPECIAL FEATURE... TROPICAL DEPRESSION TEN IS ALMOST ONSHORE NEAR 30.4N 86.7W NEAR FORT WALTON BEACH FLORIDA. THE TROPICAL STORM WARNING FOR THE GULF COAST HAS BEEN DISCONTINUED. THE DEPRESSION IS MOVING NW NEAR 8 KT. THIS MOTION IS EXPECTED TO CONTINUE TONIGHT ...BRINGING THE CENTER OF THE DEPRESSION FARTHER INLAND. THE LATEST MINIMUM CENTRAL PRESSURE REPORTED BY AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT WAS 1005 MB. RADAR AND SURFACE OBSERVATIONS INDICATE THAT THE DEPRESSION HAS NOT STRENGTHENED AND MAXIMUM SUSTAINED WINDS REMAIN NEAR 30 KT WITH GUSTS TO 40 KT IN A FEW SQUALLS. A GRADUAL WEAKENING SHOULD BEGIN TONIGHT AFTER THE CENTER MOVES FARTHER INLAND. PLEASE REFER TO THE LATEST NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT5/WTNT35 KNHC FOR MORE DETAILS. RADAR IMAGERY SHOWS BROKEN BANDS OF SCATTERED SHOWERS AND TSTMS ROTATING AROUND THE DEPRESSION. SOME OF THIS ACTIVITY HAS SPREAD WELL INLAND THROUGH THE FLORIDA PANHANDLE...SW GEORGIA AND SE ALABAMA. ISOLATED TORNADOES ARE POSSIBLE ACROSS THESE AREAS THROUGH TONIGHT. IN ADDITION TO THIS THREAT...RIP CURRENTS AND ROUGH SURF ARE A CONCERN FOR PORTIONS OF THE GULF COAST. SEE STATEMENTS FROM LOCAL WEATHER SERVICE OFFICES FOR MORE DETAILS. ...TROPICAL WAVES... A TROPICAL WAVE HAS MOVED W OF THE CAPE VERDE ISLANDS TITLED NW-SE ALONG 19N28W 6N25W MOVING W 10-15 KT. THIS ELONGATED AREA OF CYCLONIC TURNING IS EASILY SEEN ON SATELLITE IMAGERY AND DERIVED WINDS. THE WAVE ALSO SHOWS UP NICELY ON THE MIMIC TPW ANIMATION AS A LARGE MOISTENED AREA WITH THE CREST REACHING WELL INTO THE SUBTROPICS. WHILE THE SIGNATURE AND STRUCTURE IS DEFINED ...CONVECTION IS NON-EXISTENT LIKELY SUPPRESSED BY THE STABLE AIR SURROUNDING THIS FEATURE. A LOWER LATITUDE TROPICAL WAVE IS ALONG 38W S OF 15N MOVING W 10 KT. MUCH OF THE WAVE ENERGY HAS BEEN ABSORBED WITHIN THE ITCZ. THIS HAS MADE THE POSITION DIFFICULT TO PIN POINT WITH THE CURRENT AXIS DRAWN THROUGH THE VERY BROAD FAINT INVERTED V-SHAPE WITHIN THE ITCZ. ASSOCIATED SHOWERS AND TSTMS HAVE BECOME INCREASINGLY DIFFUSE SPREAD OUT BY THE MODERATE TO STRONG DIVERGENT MID TO UPPER FLOW IN THE AREA. SCATTERED MODERATE CONVECTION IS FROM 9N-12N BETWEEN 36W-44W. A WEAK TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 71W S OF 18N MOVING W 15-20 KT. THE NRN PORTION OF THE WAVE LIES UNDERNEATH AN UPPER LOW BUT THIS INTERACTION IS ONLY PRODUCING PATCHY CLOUDINESS AT THE MOMENT. THIS SHALLOW WAVE IS ONLY SEEN ON THE MIMIC TPW ANIMATION WHICH DEPICTS A NARROW MODEST MOISTURE SURGE MOVING THROUGH THE ABC ISLANDS. THIS ANIMATION ALSO VERY WELL REVEALS HOW THIS ONCE LARGE WAVE SPLIT JUST E OF 60W WITH THE NRN PORTION...WHICH CONSUMED MOST OF THE ENERGY...STILL LAGGING BEHIND E OF THE LESSER ANTILLES. MORE ON THAT FEATURE IN THE ATLC DISCUSSION SECTION. ...THE ITCZ... AXIS IS CENTERED ALONG 8N13W 10N24W 8N31W 10N41W 5N53W. BESIDES FOR THE ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE APPROACHING 40W...SCATTERED SHOWERS AND TSTMS ARE FROM 9N-13N BETWEEN 42W-51W. DISCUSSION... GULF OF MEXICO... TROPICAL DEPRESSION TEN IS THE AREA OF FOCUS THIS EVENING IN THE NE GULF. FOR DETAILS AND REFERENCES REFER TO THE SPECIAL FEATURE SECTION ABOVE. SFC OBSERVATIONS AND SATELLITE IMAGERY SHOW A WELL DEFINED TRAILING TROUGH AXIS WHICH EXTENDS SW FROM THE DEPRESSION TO 24N90W. IR IMAGERY AND LIGHTNING DATA SUGGEST THAT SCATTERED SHOWERS AND TSTMS ARE LOCATED WITHIN 60 NM OF THAT BOUNDARY. VERY DRY AIR IN THE MID AND UPPER LEVELS SURROUNDS THE DEPRESSION COVERING THE BULK OF THE W GULF. THE DRY SLOT NARROWS TO THE E OF THE DEPRESSION BUT STILL REMAINS DISTINCT ON WATER VAPOR IMAGERY. ABUNDANT DEEP MOISTURE IS POURING IN THE EXTREME SE GULF. THIS MOISTURE IS BEING DRAWN NNE BY EXTENSIVE DEEP LAYER SLY FLOW. DOPPLER RADAR AND LIGHTNING DATA INDICATE QUITE A BIT OF TSTM ACTIVITY EMBEDDED IN THE AREA S OF 25N E OF 85W. SFC REPORTS SHOW SOME GUSTY WINDS IN THIS ACTIVITY. SEVERAL STATIONS IN THE FLORIDA KEYS ARE REPORTING GUSTS NEAR OR SLIGHTLY ABOVE 30 KT. THIS MOISTURE WILL LIKELY EXPAND NWD THROUGH TOMORROW AND THEN POSSIBLY NWWD. CARIBBEAN SEA... A LARGE AREA OF DISORGANIZED SCATTERED MODERATE CONVECTION PERSISTS ACROSS THE CARIBBEAN GENERALLY W OF 76W. VISIBLE IMAGERY SHOWS SOME SPIN TO THE CLOUDS NEAR 17N81W...THOUGH THIS IS LIKELY MID-LEVEL WHEN COMPARED TO THE SFC OBSERVATIONS IN THE REGION. THERE DOES APPEAR TO BE A SFC BOUNDARY BUT THIS IS ANALYZED TO THE W OF THE MID-LEVEL VORTICITY ALONG 86W/87W FROM 13N-21N... AND THERE IS LOW CONFIDENCE IN THIS POSITION. A LARGE CONTRIBUTING COMPONENT IS IN THE UPPER LEVELS. EXTENSIVE SWLY FLOW AND DIFFLUENCE ALOFT BETWEEN THE DEPRESSION AND AN UPPER HIGH OVER NICARAGUA IS LIKELY RESPONSIBLE FOR SOME OF THE STRONGEST ACTIVITY WHICH CURRENTLY IS OVER CUBA. A FEW MODELS SHOW SOME DEVELOPMENT IN THIS REGION OVER THE NEXT COUPLE OF DAYS. HOWEVER...AT THE MOMENT THERE ARE NO SIGNS OF ORGANIZATION AND SURFACES PRESSURES ARE NOT FALLING SO ADDITIONAL DEVELOPMENT...IF ANY...IS EXPECTED TO BE SLOW TO OCCUR. THE WEATHER ACROSS THE REMAINDER OF THE REGION IS FAIRLY TRANQUIL. AN UPPER LOW IS SPINNING OVER HISPANIOLA PRODUCING A FEW SHOWERS OVER THE ISLAND AND SOME DEBRIS HIGH CLOUDINESS ACROSS PUERTO RICO. OTHERWISE...DRY STABLE AIR DOMINATES. ATLANTIC OCEAN... SCATTERED SHOWERS AND TSTMS CONTINUE OVER THE WRN ATLC AND THE BAHAMAS W OF 76W ASSOCIATED WITH THE MOIST AND UNSTABLE ENVIRONMENT E OF TROPICAL DEPRESSION TEN IN THE NE GULF AND S OF THE STATIONARY COASTAL FRONT JUST OFFSHORE THE CAROLINAS AND GEORGIA. UPPER DIFFLUENCE BETWEEN THE UPPER LOW OVER THE ERN GULF AND AN UPPER HIGH NEAR 27N72W IS ALSO SUPPORTING THIS CONVECTIVE ACTIVITY. A WEAK SFC TROUGH...ASSOCIATED WITH THE REMNANTS OF INGRID...EXTENDS ALONG 29N66W 23N69W. THIS SHALLOW SYSTEM IS ONLY GENERATING ISOLATED SHOWERS NEAR THE AXIS. THE MAIN FEATURE IN THE CENTRAL ATLC IS A LONG DRAWN OUT SFC TROUGH WHICH EXTENDS FROM A NEARLY STATIONARY 1009 MB LOW NEAR 35N47W TO A 1012 MB LOW NEAR 18N56W ALONG 32N46W 25N50W 15N57W. BASED ON SATELLITE IMAGES AND THE TPW ANIMATION...THE SRN LOW IS LIKELY PARTIALLY ASSOCIATED WITH THE NRN PORTION OF A TROPICAL WAVE CURRENTLY IN THE CENTRAL CARIB. THE NRN LOW...NON-TROPICAL IN NATURE...HAS CHANGED LITTLE SINCE YESTERDAY AND IS BEING MONITORED FOR SIGNS OF TROPICAL DEVELOPMENT. A SWATH OF MID TO HIGH LEVEL CLOUDINESS AND ISOLATED SHOWERS ARE WITHIN 240 NM E OF THE TROUGH AXIS. THE REMAINDER OF THE E ATLC IS DOMINATED BY TYPICAL SFC RIDGING S OF A 1027 MB HIGH E OF THE AZORES NEAR 38N21W. THIS IS PRODUCING LIGHT TO MODERATE NE TRADES E OF 45W...EXCEPT STRONGER NEAR THE COAST OF NW AFRICA WHERE A TIGHTER PRES GRADIENT EXISTS. IN FACT...A QSCAT PASS AROUND 20Z DEPICTED 20-25 KT WINDS NEAR THE COAST FROM 21N-28W. THE NWD MOVING UPPER LOW OVER THE ERN ATLC NEAR 30N25W HAS GAINED MOISTURE TODAY WITH SCATTERED SHOWERS POSSIBLE FROM 25N-30N BETWEEN 19W-24W. WEAK SFC RIDGING WILL GRADUALLY TAKE OVER THE WRN ATLC OVER THE NEXT COUPLE OF DAYS WHILE STRONGER RIDGING CONTINUES TO SIT OVER THE E ATLC. CONFLUENCE BETWEEN THE SFC RIDGES WILL ALLOW BROAD TROUGHING AND SCATTERED SHOWER ACTIVITY TO PERSIST OVER PARTS OF THE CENTRAL ATLC MAINLY N OF 18N...AND S OF THE NON-TROPICAL SYSTEM BEING MONITORED WELL E OF BERMUDA. $$ CANGIALOSI