000 AXNT20 KNHC 211041 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT THU 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURE... THE LOW PRESSURE AREA...ANALYZED 1005 MB...OVER THE NORTHEASTERN GULF OF MEXICO HAS BEEN MOVING NORTHWESTWARD DURING THE NIGHT AND IS NOW CENTERED ABOUT 85 NM SOUTH OF APALACHICOLA FLORIDA. SATELLITE IMAGERY...RADAR DATA...AND SURFACE OBSERVATIONS INDICATE THAT SYSTEM IS GRADUALLY BECOMING BETTER ORGANIZED... BUT DOES NOT YET HAVE THE CHARACTERISTICS OF A SUBTROPICAL OR TROPICAL CYCLONE. SQUALLS WITH GUSTY WINDS UP TO 30 TO 35 MPH HAVE BEEN REPORTED AT OFFSHORE NOAA AUTOMATED STATIONS. ENVIRONMENTAL CONDITIONS ARE FAVORABLE FOR THIS SYSTEM TO BECOME A SUBTROPICAL OR TROPICAL CYCLONE AT ANY TIME DURING THE NEXT 24 HOURS AS IT MOVES GENERALLY TOWARD THE WNW. ALL INTERESTS ALONG THE NORTHERN GULF COAST SHOULD CLOSELY MONITOR THE PROGRESS OF THIS SYSTEM...AND TROPICAL STORM WATCHES AND WARNINGS COULD BE REQUIRED FOR PORTIONS OF THIS AREA LATER TODAY. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT WILL BE INVESTIGATING THE SYSTEM IN A FEW HOURS. ...TROPICAL WAVES... A TROPICAL WAVE IS MOVING ACROSS THE CAPE VERDE ISLANDS WITH THE AXIS ALONG 23W/24W S OF 18N MOVING W 10 KT. EVEN THOUGH THE WAVE LACKS CONVECTION IT STILL SHOWS UP NICELY IN THE UW CIMSS TPW PRODUCT AND SATELLITE DERIVED WINDS. ONLY ISOLATED SHOWERS ARE ASSOCIATED WITH THE WAVE. A LOW AMPLITUDE TROPICAL WAVE IS ALONG 36W S OF 15N MOVING W 10-15 KT. SATELLITE IMAGERY DEPICTS THIS FEATURE AS A BROAD LOW-LATITUDE PERTURBATION WITHIN THE ITCZ. SCATTERED MODERATE CONVECTION IS NEAR THE INTERSECTION OF THE WAVE AND THE ITCZ FROM 8N-10N BETWEEN 33W-39W. MORE SIGNIFICANT CONVECTION IS W OF THE WAVE AXIS EMBEDDED WITHIN THE ITCZ. A WEAK TROPICAL WAVE IS OVER THE EASTERN CARIBBEAN ALONG 66W. THE MIMIC TPW ANIMATION SHOWS THE PRESENCE OF THE WAVE WITH A SURGE OF MOISTURE OVER THE ABC ISLANDS. MINIMAL SHOWER ACTIVITY IS NOTED. THE INTERACTION OF THE WAVE WITH AN UPPER LOW LOCATED JUST NORTH OF HISPANIOLA IS PRODUCING ISOLATED SHOWERS OVER DOMINICAN REPUBLIC AND COASTAL WATERS...INCLUDING THE MONA PASSAGE. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 12N17W 10N30W 10N40W 5N55W. NUMEROUS MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 90 NM EITHER SIDE OF AXIS BETWEEN 40W-50W. A LINE OF WIDELY SCATTERED MODERATE CONVECTION IS ALONG 6N/7N EAST OF 20W. DISCUSSION... GULF OF MEXICO... ALL THE ATTENTION THIS MORNING REMAINS FOCUSED ON THE DEEP LAYER LOW IN THE ERN GULF LOCATED NEAR 28N85W. DOPPLER RADAR INDICATES CURVED BANDS OF SHOWERS WITH EMBEDDED TSTMS OVER SOUTH GEORGIA AND THE FLORIDA BIG BEND. SEE SPECIAL FEATURE SECTION FOR MORE DETAILS. A SWATH OF VERY DRY MID TO UPPER AIR CONTINUES TO WRAP AROUND THE PERIPHERY OF THE UPPER-LEVEL LOW THROUGH THE MIDDLE AND WESTERN GULF AND NE MEXICO THEN E TO NE ACROSS THE SE GULF AND SOUTH FLORIDA. AN UPPER TROUGH EXTENDS FROM THE LOW TO THE MEXICAN COAST NEAR TAMPICO. UPPER RIDGING...CENTERED OVER TEXAS...DOMINATES THE FAR NW PORTION WHILE A WEAKENING UPPER LOW CONTINUES TO MOVE SLOWLY OVER CENTRAL MEXICO NEAR 20N100W. DIFFLUENCE ALOFT E OF THIS UPPER LOW IS PRODUCING ISOLATED SHOWERS IN THE BAY OF CAMPECHE. ELSEWHERE AT THE SURFACE MODERATE RIDGING DOMINATES THE WESTERN GULF EXTENDING SWD FROM A 1017 MB HIGH IN ARKANSAS. CONDITIONS OVER THE NEXT COUPLE OF DAYS HIGHLY DEPEND UPON THE SPECIAL FEATURE. MODEL GUIDANCE BRINGS THIS SYSTEM TO THE NORTHERN GULF COAST ON SATURDAY. HOWEVER...REGARDLESS OF DEVELOPMENT...MOISTURE WILL LIKELY BE ON THE INCREASE ACROSS THE E GULF DRAWN IN BY EXTENSIVE DEEP SLY FLOW FROM THE TROPICS. CARIBBEAN SEA... CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION PERSIST OVER THE WESTERN CARIBBEAN WEST OF 78W. THIS ACTIVITY IS ASSOCIATED WITH A SFC TROUGH THAT RUNS FROM 17N84W TO 10N78W AND A DIFFLUENT PATTERN ALOFT RELATED TO AN UPPER RIDGE THAT COVERS MOST OF THE WEST AND CENTRAL CARIBBEAN...ANCHORED ON A HIGH OVER THE SW CARIBBEAN NEAR 14N79W. THIS RIDGE...COUPLED WITH THE PANAMANIAN OR COLOMBIAN LOW IS ALSO ENHANCING CONVECTION OVER WESTERN VENEZUELA AND NORTHERN COLOMBIA. NW TO WLY UPPER FLOW...SET UP BETWEEN THE UPPER RIDGE AND AN UPPER-LEVEL LOW LOCATED JUST N OF HISPANIOLA COVERS THE REGION BETWEEN 64W-74W. AN UPPER HIGH SITUATED E OF THE LESSER ANTILLES EXTENDS A RIDGE INTO THE FAR E PORTION OF THE BASIN. THE SURFACE PRES GRADIENT REMAINS FAIRLY RELAXED ACROSS THE AREA...DUE TO THE LOW IN THE ERN GULF AND WEAK TROUGHING IN THE WRN ATLC. THIS IS KEEPING THE TRADE WINDS MOSTLY LIGHT...EXCEPT SLIGHTLY STRONGER NEAR THE COAST OF COLOMBIA. LIGHT TO MODERATE TRADES ARE EXPECTED TO PERSIST TODAY AND SHOWER ACTIVITY WILL REMAIN FOCUSED IN THE WRN CARIB. ATLANTIC OCEAN... SHOWERS AND TSTMS CONTINUE OVER THE WRN ATLC AND THE NW BAHAMAS W OF 76W ASSOCIATED WITH THE MOIST AND UNSTABLE ENVIRONMENT E OF THE DEEP LAYER LOW IN THE EASTERN 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 28N72W IS ALSO HELPING TO INDUCE THIS CONVECTIVE ACTIVITY. A WEAK SFC TROUGH ASSOCIATED WITH THE REMNANTS OF INGRID EXTENDS ALONG 66W/67W FROM 21-27N. ONLY ISOLATED SHOWERS ARE NEAR THE TROUGH AXIS. THIS FEATURE IS INTERACTING WITH THE UPPER LOW LOCATED JUST N OF HISPANIOLA. THE CENTRAL ATLC SFC PATTERN IS DOMINATED BY A 1010MB LOW NEAR 34N46W OR ABOUT 870 NM EAST OF BERMUDA. THIS NEARLY STATIONARY NON-TROPICAL LOW IS BEING MONITORED FOR SIGNS OF TROPICAL DEVELOPMENT. A SFC TROUGH EXTENDS FROM THE LOW ALONG 25N50W 15N55W. SCATTERED MODERATE CONVECTION IS JUST EAST AND WITHIN 160 NM OF THE TROUGH AXIS. THE REMAINDER OF THE E ATLC IS DOMINATED BY TYPICAL SFC RIDGING S OF A 1026 MB HIGH E OF THE AZORES NEAR 39N21W. THIS IS PRODUCING MODERATE NE TRADES E OF 35W...STRONGER NEAR THE COAST OF NW AFRICA WHERE A TIGHTER PRES GRADIENT EXISTS. UPPER RIDGING GENERALLY DOMINATES THE REMAINDER OF THE TROPICAL ATLC. $$ GR