000 AXNT20 KNHC 210548 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURE... THE LOW PRESSURE AREA...ANALYZED 1005 MB...IN THE GULF OF MEXICO HAS BEEN MEANDERING DURING THE PAST FEW HOURS AND IS NOW LOCATED ABOUT 100 NM WEST OF TAMPA FLORIDA. THERE HAS BEEN NO SIGNIFICANT CHANGE IN ORGANIZATION THIS EVENING BUT BANDS OF HEAVY SQUALLS ARE FORMING TO THE NORTH OF THE CENTER...AND ARE ALREADY AFFECTING COASTAL SECTIONS OF THE FLORIDA PANHANDLE. SFC OBSERVATIONS ARE CURRENTLY REPORTING WINDS MOSTLY IN THE 15-25 KT RANGE...STRONGEST N OF THE CENTER WHERE THE PRESSURE GRADIENT IS TIGHTENED BETWEEN THE LOW AND RIDGING TO THE NW. ENVIRONMENTAL CONDITIONS ARE FAVORABLE FOR THIS SYSTEM TO BECOME A SUBTROPICAL OR TROPICAL CYCLONE AT ANY TIME DURING THE NEXT 24 HOURS AS THE LOW MOVES SLOWLY TOWARD THE WEST-NORTHWEST. ALL INTERESTS ALONG THE NORTHERN GULF COAST SHOULD CLOSELY MONITOR THE PROGRESS OF THIS SYSTEM...AND TROPICAL STORM WATCHES AND WARNINGS COULD BE PROMPTLY REQUIRED FOR PORTIONS OF THIS AREA TODAY. ...TROPICAL WAVES... A TROPICAL WAVE IS MOVING ACROSS THE CAPE VERDE ISLANDS WITH THE AXIS ALONG 22W/23W S OF 18N MOVING W 10 KT. SHOWERS AND TSTMS HAVE DIMINISHED OVER THE PAST SEVERAL HOURS WITH ONLY ISOLATED SHOWERS REMAINING WITHIN 50 NM OF THE WAVE AXIS. EVEN THOUGH THE WAVE LACKS CONVECTION IT STILL SHOWS UP NICELY IN THE UW CIMSS TPW PRODUCT AND SATELLITE DERIVED WINDS. A LOW AMPLITUDE TROPICAL WAVE IS ALONG 35W/36W S OF 15N MOVING W 10-15 KT. SATELLITE IMAGERY DEPICTS THIS FEATURE AS A BROAD LOW-LATITUDE PERTURBATION WITHIN THE ITCZ. DISORGANIZED SCATTERED SHOWERS ARE WITHIN 150 NM EITHER SIDE OF THE WAVE AXIS. 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. MINIMAL SHOWER ACTIVITY IS NOTED. ...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. WIDELY SCATTERED MODERATE CONVECTION IS FROM 5N-11N E OF 19W TO THE COAST OF AFRICA. DISCUSSION... GULF OF MEXICO... ATTENTION REMAINS FOCUSED ON THE DEEP LAYER LOW IN THE ERN GULF LOCATED NEAR 28N85W. DOPPLER RADAR INDICATES THAT THE ASSOCIATED DISORGANIZED SHOWER AND TSTM ACTIVITY IS GENERALLY N OF 25N E OF 87W. SEE SPECIAL FEATURE SECTION FOR 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 THEN E TO NE ACROSS THE WRN TIP OF CUBA AND THE SE GULF. A NARROW DRY SLOT CONTINUES NWD ACROSS THE E PART OF THE FL PENINSULA. 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. 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 ARE OVER THE WESTERN CARIBBEAN WEST OF 78W. THIS ACTIVITY IS ASSOCIATED WITH A SFC TROUGH THAT RUNS FROM 17N83W TO 9N78W AND A DIFFLUENT PATTERN ALOFT RELATED TO AN UPPER RIDGE THAT COVERS MOST OF THE WEST AND CENTRAL CARIBBEAN...ANCHORED ON A HIGH OVER NICARAGUA. THIS RIDGE...COUPLED WITH THE ITCZ 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 SE PORTION OF THE CARIBBEAN SEA. 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. LOOKING AHEAD...LIGHT TO MODERATE TRADES ARE EXPECTED TO PERSIST TODAY AND SHOWER ACTIVITY WILL REMAIN FOCUSED IN THE WRN CARIB. ATLANTIC OCEAN... SCATTERED SHOWERS AND TSTMS CONTINUE OVER THE WRN ATLC AND THE NW BAHAMAS W OF 75W 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 THROUGH N FLORIDA. UPPER DIFFLUENCE BETWEEN THE UPPER LOW OVER THE ERN GULF AND AN UPPER HIGH NEAR 29N72W IS ALSO HELPING TO INDUCE THIS CONVECTIVE ACTIVITY. A WEAK SFC TROUGH ASSOCIATED WITH THE REMNANTS OF INGRID EXTENDS ALONG 67W/68W FROM 20N-26N. SCATTERED SHOWERS AND ISOLATED TSTMS ARE RELATED TO THE TROUGH MAINLY ON THE NORTHERN END. THIS FEATURE IS INTERACTING WITH THE UPPER LOW LOCATED JUST N OF HISPANIOLA. THE CENTRAL ATLC SFC PATTERN IS DOMINATED BY A 1011 MB LOW NEAR 33N46W 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 24N52W 15N56W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE FOUND MAINLY EAST AND WITHIN 150 NM OF THE TROUGH AXIS. THE REMAINDER OF THE E ATLC IS DOMINATED BY TYPICAL SFC RIDGING S OF A 1027 MB HIGH NE OF THE AZORES NEAR 39N22W. THIS IS PRODUCING MODERATE NE TRADES E OF 35W...STRONGER NEAR THE COAST OF NW AFRICA WHERE A TIGHTER PRES GRADIENT EXISTS. A WEAK SFC TROUGH IS ALONG 28W/29W ASSOCIATED WITH A BENIGN UPPER LOW NEAR 29N27W WHILE UPPER RIDGING GENERALLY DOMINATES THE REMAINDER OF THE TROPICAL ATLC. $$ GR