[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 091756
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT JUL 09 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND 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...
HURRICANE DENNIS WAS CENTERED NEAR 25.3N 84.2W AT 1800 UTC
MOVING NW 12 KT.  THIS POSITION IS ABOUT 310 MILES SOUTH OF
APALACHICOLA FLORIDA AND ABOUT 445 MILES SOUTHEAST OF PASCAGOULA
MISSISSIPPI.  MAXIMUM SUSTAINED WINDS ARE 85 KT GUSTING TO 105
KT WITH A MINIMUM CENTRAL PRESSURE OF 964 MB.  SEE THE LATEST
NHC PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34
KNHC AND THE FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.  DENNIS HAS REDEVELOPED
AN EYE ON SATELLITE PICTURES WITH DATA FROM RECONNAISSANCE
AIRCRAFT SUGGESTING A SLOW INTENSIFICATION.  THERE IS A LARGE
AREA OF SHOWERS/TSTMS TO THE SE OF THE CENTER WITH SCATTERED
MODERATE CONVECTION FROM S FLORIDA TO 20N BETWEEN 79W-82W.
RELATIVELY LIGHT SHEAR AND WARM WATER SHOULD ALLOW THE STORM TO
CONTINUE TO INTENSIFY FOR THE SHORT-TERM.  A FEW SQUALLS ARE
ALREADY AFFECTING THE FLORIDA PANHANDLE DUE TO THE RELATIVELY
LARGE SIZE OF THE HURRICANE.

...TROPICAL WAVES...

CENTRAL ATLC TROPICAL WAVE ALONG 36W S OF 18N MOVING W 10-15 KT
WITH A 1013 MB LOW ON THE WAVE NEAR 10.5N.  THIS LOW HAS BECOME
A LITTLE BETTER-ORGANIZED THAN YESTERDAY WITH BANDING FEATURES
COMING ON THE N SIDE AND QUIKSCAT INDICATING A CLOSED SURFACE
CIRCULATION.  HOWEVER CONVECTION REMAINS MEAGER AS THE SYSTEM IS
ENTANGLED WITH A LOT OF MID/UPPER DRY AIR.  A 1014 MB LOW WAS
SPAWNED OFF THIS WAVE A FEW DAYS AGO AND IS NOW DRIFTING
EASTWARD IN THE ITCZ NEAR 10.5N24.5W WITHOUT ANY DEEP
CONVECTION.  THE LEADING EDGE OF MOISTURE ASSOCIATED WITH THE
WAVE COULD REACH THE WINDWARD ISLANDS BY WED.  WIDELY SCATTERED
MODERATE CONVECTION IS WITHIN 90 NM OF THE LOW CENTER IN THE
WESTERN SEMICIRCLE.

E CARIBBEAN TROPICAL WAVE ALONG 63W S OF 15N MOVING W 10-15 KT.
THE WAVE IS COMBINING WITH A MID/UPPER LEVEL TROUGH TO ITS WEST
TO PRODUCE WIDELY SCATTERED TSTMS BETWEEN GUADELOUPE AND
N-CENTRAL VENEZUELA FROM 60W-66W.

...ITCZ...

ITCZ AXIS IS ALONG 11N16W 6N45W 9N61W.  WIDELY SCATTERED
MODERATE S OF 10N W OF 55W.  SIMILAR CONVECTION IS WITHIN 120 NM
OF 7N35W.  SCATTERED MODERATE CONVECTION IS FROM THE COAST OF
AFRICA TO 20W BETWEEN 7N-12N.

...DISCUSSION...

GULF OF MEXICO...
HURRICANE DENNIS DOMINATES THE WEATHER STORY FOR THE EASTERN
GULF OF MEXICO WHILE THE WESTERN GULF HAS A MID/UPPER TROUGH
FROM SW LOUISIANA SOUTHWARD INTO THE BAY OF CAMPECHE.  VERY DRY
AIR ALOFT IS W OF 90W WITH A LITTLE COLD-AIR INSTABILITY IN THE
TROUGH AXIS N OF 27N CONTRIBUTING TO A FEW SHOWERS/TSTMS NEAR
THE SE TEXAS/SW LOUISIANA COASTS.  ANTICYCLONIC FLOW COVERS THE
E GULF AROUND DENNIS WITH A FAVORABLE ENVIRONMENT FOR
REINTENSIFICATION SEEN ALOFT.  BANDS OF SHOWERS/TSTMS ARE
SPREADING ACROSS THE FLORIDA PENINSULA WITH ISOLATED TORNADOES
POSSIBLE.  DENNIS SHOULD CONTINUE MOVING IN A GENERAL NW TO NNW
DIRECTION TOWARD THE CENTRAL GULF COAST BETWEEN THE TROUGH OVER
THE W GULF AND A MID/UPPER RIDGE OVER THE W ATLC INTO NW
FLORIDA.  BANDS OF RAIN SHOULD BE REACHING THE EASTERN PART OF
THE HURRICANE WARNING AREA BY SUN MORNING.

CARIBBEAN SEA...
EFFECTS FROM DENNIS ARE WANING AS THE CYCLONE PULLS FARTHER AWAY
FROM THE AREA.  HOWEVER VERY HEAVY RAIN CONTINUES FOR CUBA W OF
79W CONTINUING SOUTHWARD THRU THE CAYMAN ISLANDS.  THE HEAVIEST
RAIN SHOULD SHIFT INTO EXTREME W CUBA OVERNIGHT THEN LIFT NORTH
BY SUN BRINGING MUCH DRIER CONDITIONS BY LATE IN THE WEEKEND.
ANTICYCLONIC FLOW ALOFT COVERS THE W AND CENTRAL CARIBEAN WITH
PLENTIFUL HIGH CLOUDS W OF 70W DUE TO CIRRUS OUTFLOW FROM THE
HURRICANE.  FARTHER E... A MID/UPPER TROUGH IS ALONG 23N59W TO
11N67W (JUST E OF THE ABC ISLANDS) AND IS BRINGING VERY DRY AIR
ALOFT OVER THE LEEWARD ISLANDS INTO PUERTO RICO.  HOWEVER SW
WINDS TO THE E OF THE TROUGH AXIS ARE CAUSING WIDELY SCATTERED
TSTMS IN THE SE CARIBBEAN DUE TO INTERACTION WITH A TROPICAL
WAVE.  MOST OF THIS MOISTURE SHOULD BYPASS PUERTO RICO BUT A
SLIGHTLY ENHANCED CHANCE OF RAIN COULD MOVE IN BY LATE SUN...
INTO HISPANIOLA BY MON.

ATLANTIC OCEAN...
LITTLE CHANGE FROM YESTERDAY WITH MID/UPPER RIDGING EXTENDING
FROM NE FLORIDA TO JUST NW OF BERMUDA WITH A WEAK TROUGH BENEATH
THE RIDGE FROM PUERTO RICO TO 26N71W. OUTFLOW FROM DENNIS COVERS
THE BAHAMAS AND THE REST OF THE SW ATLC SW OF A LINE FROM
HISPANIOLA TO SE GEORGIA.  A MID/UPPER TROUGH IS ALONG26N57W
THRU THE VIRGIN ISLANDS.  MODERATE/STRONG SUBSIDENCE COVERS THE
CENTRAL ATLC W OF 40W TO THE TROUGH AXIS BETWEEN 10N-30N.  A
BROAD TROUGH IS AT THE NORTHERN FRINGE OF THE CENTRAL ATLC FROM
25N45W TO 31N30W THOUGH NOT PRODUCING ANY SIGNIFICANT WEATHER.
THE TYPICAL AFRICAN ANTICYCLONE IS OVER WESTERN SAHARA NEAR
22N16W WITH RIDGE AXIS WSW TO 14N52W.  INVERTED TROUGH IS ALONG
40W S OF 18N CREATING A SMALL BREAK IN THE RIDGE.  ELY FLOW IS A
BIT DIFFLUENT S OF THE RIDGE.. SUPPORTING TSTMS NEAR THE TROICAL
WAVE AND THE FAR E ATLC ITCZ.  PRESSURES ARE A LITTLE
HIGHER-THAN-AVERAGE IN THE DEEP TROPICAL ATLC THOUGH THEY ARE A
BIT LESS-THAN-AVERAGE IN THE SUBTROPICS... SUPPORTING A PRESSURE
GRADIENT WEAKER THAN AVERAGE AND ANOTHER DAY OF WEAK TRADEWINDS.

$$
BLAKE


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