[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 031803
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU AUG 03 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

TROPICAL STORM CHRIS IS EXPECTED TO WEAKEN TO A DEPRESSION LATER
TODAY...WITH LOW TO MID LEVEL DRY AIR AND SHEAR HAVEN TAKEN ITS
TOLL. THE CENTER OF TROPICAL STORM CHRIS WAS LOCATED NEAR 20.7
NORTH 67.7 WEST OR ABOUT 225 NM EAST-SOUTHEAST OF GRAND TURK
ISLAND AT 03/1800 UTC. CHRIS IS MOVING TOWARD THE WEST-NORTHWEST
NEAR 10 KT.  THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1012 MB.
THE MAXIMUM SUSTAINED WINDS REMAIN 35 KT WITH HIGHER GUSTS.
PLEASE REFER TO THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT3/ WTNT23 KNHC AND THE PUBLIC ADVISORY
MIATCPAT3/WTNT33 KNHC FOR MORE DETAILS. CHRIS  IS EXPECTED TO
PRODUCE TOTAL RAINFALL AMOUNTS OF 1 TO 3 INCHES WITH ISOLATED
TOTALS OF UP TO 5 INCHES OVER THE HIGHER TERRAIN OF PUERTO
RICO...THE U.S. AND BRITISH VIRGIN ISLANDS...AND THE DOMINICAN
REPUBLIC.  RAINFALL AMOUNTS OF 1 TO 2 INCHES ARE POSSIBLE OVER
THE SOUTHEAST BAHAMAS...THE TURKS AND CAICOS ISLANDS...AND
NORTHERN HAITI THROUGH FRIDAY. THE CLOUD TOPS ASSOCIATED WITH
CHRIS REMAIN MUCH WARMER THAN THEY WERE YESTERDAY AND EVEN LAST
NIGHT. DISPLACED...SCATTERED SHOWER AND THUNDERSTORM ACTIVITY IS
GENERALLY CONFINED TO THE REGION S AND SE OF THE CENTER FROM
17.5N N TO 19.5N BETWEEN 65.3W AND 67.8W. HE UW-CIMMS SHEAR
ANALYSIS DEPICTS 20 TO 30 KTS OF NORTHERLY SHEAR AFFECTING THESE
SHOWERS AND THUNDERSTORMS...ASSOCIATED WITH AN UPPER LEVEL LOW
TO THE NE OF CHRIS CENTERED NEAR 24N55W AND ITS INTERACTION WITH
AN UPPER RIDGE WHOSE AXIS EXTENDS EAST THROUGH HISPANIOLA.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE ALONG 43W/44W S OF 17N...OR
ABOUT 1000NM E OF THE LESSER ANTILLES...IS MOVING WEST 15-20 KT.
VISIBILE IMAGERY THIS AFTERNOON DEPICTS SOME BROAD CYCLONIC
CURVATURE BUT THE SIGNAL IS A BIT NOISY DUE TO ITCZ ACTIVITY
ALONG WITH BROAD UPPER EASTERLY FLOW OVER THE AREA. MOST OF THE
SHOWER AND TSTM ACTIVITY IN THE VICINITY LIES EAST OF THE
WAVE...MORE ASSOCIATED WITH THE ITCZ/MONSOON TROUGH. ONLY
ISOLATED SHOWERS AND TSTMS ARE NOTED WITHIN 250NM OF EITHER SIDE
OF THE WAVE AXIS.

A TROPICAL WAVE IS MOVING W NEAR 15 KT THROUGH THE SW CARIBBEAN
SEA ALONG 79W S OF 13N. SHIP AND SURFACE OBSERVATIONS SHOW A
CLEAR CYCLONIC CURVATURE ABOUT THE WAVE AXIS...THOUGH THERE IS
VERY LITTLE SIGNIFICANT CONVECTION NEAR THE WAVE. THE CARIBBEAN
PORTION OF THE WAVE IS DOMINATED BY DRY AIR AND FAIR
WEATHER...WITH JUST A SMALL PATCH OF MODERATE CONVECTION NOTED
IN THE GULF OF PANAMA NEAR 4N81W.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N12W 9N40W 7N46W AND INLAND THROUGH
SOUTH AMERICAN TO NEAR 8N77W.  SCATTERED MODERATE/ISOLATED
STRONG CONVECTION LIES FROM 3N TO 14N BETWEEN 10W AND 25W WHICH
COVERS A PORTION OF THE W AFRICAN COAST. ANOTHER AREA OF
SCATTERED SHOWERS AND THUNDERSTORMS WITH EMBEDDED ISOLATED
MODERATE CONVECTION LIES FROM 5N TO 13N BETWEEN 27W AND 41W.

...DISCUSSION...
THE GULF OF MEXICO...
THE MOST ACTIVE WEATHER IN THE GULF THIS AFTERNOON LIES IN THE
WESTERN BAY OF CAMPECHE...WHERE A CLUSTER OF MODERATE CONVECTION
LIES FROM 18N TO 24N BETWEEN 92W AND 98W. THIS IS ASSOCIATED
WITH UPPER DIFFLUENCE BETWEEN AN UPPER LOW CENTERED NEAR DEL RIO
TEXAS AND UPPER RIDGING TO ITS SOUTH. JUST EAST OF THIS REGION
LIES A SWATH OF DRY AIR FROM 21N TO 30N BETWEEN 88W AND 94W.
ISOLATED SHOWER AND THUNDERSTORM ACTIVITY IS DOTTING THE AREA
BETWEEN THE YUCATAN CHANNEL AND THE CENTRAL GULF COAST...IN A
REGION OF WEAK UPPER DIFFLUENCE BETWEEN AN UPPER TROF AXIS
EXTENDING WSW FROM ITS CENTER OVER THE BAHAMAS AND UPPER RIDGING
OVER MUCH OF THE SE/MID ATLANTIC STATES. THE SURFACE PATTERN IN
THE GULF REMAINS FAIRLY BENIGN WITH A 1019MB SURFACE HIGH
PRESSURE CENTER ANALYZED JUST SOUTH OF PENSACOLA...AND WINDS
GENERALLY BELOW 15KT/SEAS BELOW 4 FT. SIMILAR CONDITIONS
EXPECTED THROUGH THE NEXT 48 HOURS.

THE CARIBBEAN SEA...
DESPITE THERE BEING A TROPICAL STORM JUST NORTH OF PUERTO
RICO...THE MOST ACTIVE CONVECTION IN THE CARIBBEAN THIS
AFTERNOON LIES IN THE NW PORTION BETWEEN THE YUCATAN PENINSULA
AND WRN CUBA...WHERE SCATTERED MODERATE CONVECTION LIES FROM 18N
TO 23N BETWEEN 80W AND 87W. THIS IS ASSOCIATED WITH UPPER
DIFFLUENT FLOW BETWEEN UPPER RIDGING EXTENDING EAST THROUGH THE
YUCATAN/BELIZE/NW CARIBBEAN AND THE WELL-DEFINED UPPER LOW
CENTERED OVER THE NW BAHAMAS. MUCH OF THE REMAINDER OF THE
CARIBBEAN SEA IS DOMINATED BY ANTICYCLONIC TURNING...DRY
AIR...AND FAIR WEATHER. THE EXCEPTION IS THE MOISTURE AND
SHEARED SHOWERS/THUNDERSTORMS FROM TS CHRIS SPREADING N TO S
INTO THE NE CARIBBEAN WATERS S OF PUERTO RICO AND THE NORTHERN
LEEWARD ISLANDS. AT THE SURFACE 10 TO 25 KT E TO SE TRADE WINDS
ARE DOMINATING ON THE SW SIDE OF THE ATLANTIC HIGH. THE
STRONGEST SWATH OF TRADE WINDS ARE NOTED IN THE CENTRAL
CARIBBEAN BETWEEN 70W AND 80W...AS THE HIGH INTERACTS WITH THE
COLOMBIAN LOW.

THE ATLANTIC OCEAN...
A RATHER LARGE UPPER LEVEL LOW CONTINUES TO DRIFT WESTWARD NOW
CENTERED OVER THE WRN BAHAMAS NEAR 26N78W. THIS LOW IS AIDING IN
THE DEVELOPMENT OF A FEW SHOWERS OVER THE BAHAMAS AND SOUTH
FLORIDA. A BROAD FLAT UPPER RIDGE LIES TO THE N OF THE UPPER LOW
EXTENDING FROM THE MID-ATLANTIC U.S. TO BERMUDA. A MID-UPPER
LEVEL TROUGH DIGS INTO THE CENTRAL ATLC BEYOND 32N44W TO ANOTHER
UPPER LOW LOCATED TO THE NE OF TROPICAL STORM CHRIS CENTERED
NEAR 24N55W. THIS IS THE FEATURE THAT IS PROVIDING NORTHERLY
VERTICAL WIND SHEAR ACROSS CHRIS'S CICRULATION SHEARING MUCH OF
IT'S PREVIOUS DEEP CONVECTION...REMOVING IT WELL S OF THE
EXPOSED LOW LEVEL CENTER. SEE THE SPECIAL FEATURE SECTION FOR
MORE DETAILS. THE REMAINDER OF THE ATLC IS DOMINATED BY A LARGE
SCALE UPPER RIDGE ANCHORED BY A HIGH CENTER NEAR 21N36W. PLENTY
OF DRY/STABLE UPPER LEVEL AIR EXISTS IN THE ATLC UNDER THE
INFLUNECE OF THIS RIDGING E OF 55W. AN AREA OF UPPER DIFFFLUENCE
ON THE W PERIPHERY OF THE LARGE SCALE RIDGE IS PRODUCING
SCATTERED SHOWERS AND TSTRMS FROM THE NRN LEEWARD ISLANDS TO 36N
BETWEEN 53W-63W. AT THE SURFACE...BESIDES FOR THE TROPICAL STORM
AND THE TROPICAL WAVE...HIGH PRES RIDGING IS THE THEME SUPPORTED
BY A 1026 MB HIGH ABOUT 200 NM ENE OF THE AZORES. A WEAKENING
COLD FRONT AND SFC TROUGH ASSOCIATED WITH THE MID-UPPER TROUGH
IN THE CENTRAL ATLC ARE JUST N OF THE DISCUSSION AREA.
OVERALL...NO BIG SURFACE PATTERN CHANGES ARE EXPECTED OVER THE
NEXT DAY OR TWO.

$$
WILLIS/CANGIALOSI


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