[Tropical] Tropical Weather Discussion

[EMWIN Server]

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




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