000 AXNT20 KNHC 172358 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE OCT 17 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN 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...WEATHER OBSERVATIONS...RADAR... AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2345 UTC. ...TROPICAL WAVES... AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 37W SOUTH OF 18N MOVING WEST NEAR 10 KT. CYCLONIC TURNING REMAINS EVIDENT IN THE LOW TO MID CLOUD FIELD ESPECIALLY FROM 11N-18N BETWEEN 34W-40W. ISOLATED SHOWERS/TSTMS NOTED WITHIN 150NM OF THE WAVE AXIS...WITH DISTINCT UPPER SW FLOW OVER THE AREA IS STRETCHING THE ASSOCIATED HIGH CLOUDS TO THE NE. A TROPICAL WAVE IS ALONG 66W/67W MOVING W 10 TO 15 KT. NUMEROUS MODERATE/ISOLATED STRONG CONVECTION IS FROM 12N-16N BETWEEN 62W-69W...THOUGH IT IS UNCLEAR WHAT IS ASSOCIATED WITH THE WAVE AND WHAT IS ASSOCIATED WITH THE SURFACE TROUGH EXTENDING S FROM THE LOW JUST N OF PUERTO RICO. THIS IS ALSO A REGION OF UPPER DIFFLUENCE WHICH IS HELPING SUPPORT THE CONVECTION. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 10N13W 10N25W 12N34W 8N43W 5N53W. SCATTERED MODERATE TO STRONG CONVECTION IS OVER THE W COAST OF AFRICA AND ADJACENT ATLC WATERS FROM 7N-13N BETWEEN 10W-16W. ISOLATED MODERATE CONVECTION NOTED FROM 4N-15N BETWEEN 25W-34W. SMALL PATCH OF MODERATE CONVECTION NEAR 10N42W...WITH SIMILAR CLUSTERS OFF THE COAST OF FRENCH GUIANA AND SURINAME. ...DISCUSSION... GULF OF MEXICO... MAIN FEATURE IN THE GULF THIS EVENING IS THE SQUALL LINE EXTENDING NE THROUGH THE NRN GULF BETWEEN NEW ORLEANS AND FORT WALTON BEACH FLORIDA. THIS IS ASSOCIATED WITH A COMPLEX SURFACE PRESSURE PATTERN OVER THE SE STATES THAT CONSISTS OF A 1006MB LOW OVER NRN ALABAMA...THAT HAS A WARM FRONT EXTENDING TO THE SE TO WRN GEORGIA AND THEN NE THROUGH THE CAROLINAS...AND A DYING STATIONARY FRONT EXTENDING TO THE SW FROM THE LOW TO LOUISIANA. THE REMAINDER OF THE GULF REMAINS DOMINATED BY 10-20 KT SLY FLOW AT THE SURFACE BETWEEN HIGH PRESSURE WELL NE OF THE AREA AND LOWER PRESSURE OVER MEXICO. THE UPPER LEVEL PATTERN OVER THE GULF REMAINS DOMINATED BY A MID TO UPPER HIGH WITH AN ESTIMATED CENTER NEAR 24N92W. LOOK FOR THE SQUALL LINE TO CONTINUE MOVING SLOWLY E THOUGH THE N/NE GULF THOUGH WILL LIKELY BECOME LESS PRONOUNCED WITH MOST OF THE UPPER ENERGY WELL NE OF THE AREA. SW PORTION OF AN ATLC SFC RIDGE ALSO LOOKS TO BUILD INTO TOMORROW ACROSS THE ERN GULF SO WINDS SHALL DIMINISH A NOTCH...EXCEPT FAR WRN GULF WHERE GRADIENT WILL BE TIGHTER WITH LOWER PRESSURE OVER MEXICO. CARIBBEAN SEA... MID TO UPPER LEVEL ANTICYCLONIC FLOW PERSISTS OVER THE CARIBBEAN W OF 67W...AROUND THE LARGE HIGH OVER THE WRN GULF. MUCH OF THIS PORTION OF THE CARIBBEAN ALSO UNDER THE INFLUENCE OF DRY MID TO UPPER AIR AND FAIR WEATHER..ASIDE FROM A FEW ISOLATED SHOWERS/TSTMS BETWEEN COLOMBIA AND HISPANIOLA. A VERY ELONGATED UPPER TROUGH FROM THE ATLC EXTENDS S THROUGH THE ERN CARIBBEAN E OF 67W. UPPER DIFFLUENCE BETWEEN THIS FEATURE AND THE UPPER HIGH FROM THE GULF IS HELPING SUPPORT THE CONVECTION NEAR THE TROPICAL WAVE ALONG 67W...ALONG WITH THE SFC TROUGH EXTENDING S FROM THE LOW JUST N OF PUERTO RICO. LOW LEVEL FLOW LIGHT FAIRLY LIGHT AND CYCLONIC AROUND THE SFC FEATURES IN THE ERN CARIBBEAN. LIGHT/VARIABLE FLOW IN THE SW CARIBBEAN WITH SE FLOW 5-15KT IN THE NW CARIBBEAN AROUND HIGH PRESSURE TO THE NE. SIMILAR CONDITIONS EXPECTED THROUGH TOMORROW. ATLANTIC OCEAN... MID TO UPPER ANTICYCLONIC FLOW DOMINATES THE SW NORTH ATLC AROUND ITS ORIGIN IN THE WRN GULF. THIS IS HELPING TO PUSH ABUNDANT MID TO UPPER MOISTURE WITH SCATTERED SHOWERS SOUTH OFF THE FL AND SE US COAST. SURFACE HIGH PRESSURE AND 10-20KT SE FLOW ALSO UNDER CONTROL HERE...SW OF THE 1026MB CENTER NEAR THE CANADIAN MARITIMES. LOW LEVEL CONFLUENCE BETWEEN THIS HIGH AND THE 1018 MB SFC HIGH IN THE CENTRAL ATLC NEAR 30N38W IS SUPPORTING THE TROUGH EXTENDING NE FROM THE LOW JUST N OF PUERTO RICO TO 26N57W...ALONG WITH THE COLD FRONT THAT EXTENDS NE FROM THIS POINT TO THE SFC LOW OUT OF THE AREA NEAR 39N46W. ASSOCIATED ISOLATED MODERATE CONVECTION FROM 18N-28W BETWEEN 50W-67W...WITH THE MOST PRONOUNCED CLUSTER JUST E OF THE SFC LOW N OF PUERTO RICO. THIS LOW EXPECTED TO DRIFT SLOWLY TO THE E THROUGH 24 HRS. A VERY ELONGATED UPPER TROUGH EXTENDS S THROUGH THE AREA BETWEEN 54W-65W. A SHORTWAVE UPPER RIDGE IS FROM 13N-27N ALONG 50W/51W. WEAK UPPER LOW NEAR 22N44W WITH AN UPPER HIGH NEAR 32N41W. UPPER TROUGHING EXTENDS SW FROM THE DEEP LAYER LOW OFF PORTUGAL. UPPER SW FLOW BETWEEN THIS FEATURE AND THE UPPER HIGH OVER WRN AFRICA IS PRODUCING SW SHEAR OVER THE TROPICAL WAVE ALONG 37W AND THE SURROUNDING AREA. $$ WILLIS