[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 071759
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU JUL 07 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 CENTERED NEAR 18.6N 76.1W OR ABOUT 65 MILES NE
OF KINGSTON JAMAICA...AND 105 MILES SSW OF GUANTANAMO CUBA...
MOVING NW 13 KT. MAXIMUM SUSTAINED WIND 95 KT GUSTS TO 115
KT...MAKING DENNIS A STRONG CATEGORY 2 HURRICANE ON THE
SAFFIR-SIMPSON SCALE. ESTIMATED MINIMUM CENTRAL PRESSURE
REPORTED BY AN AIR FORCE HURRICANE HUNTER IS 962 MB. SEE 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. A SMALL EYE DEVELOPED
WITH DENNIS THIS MORNING AS THE SYSTEM STRENGTHENED TO CATEGORY
2 STATUS. MORE RECENTLY...THE EYE HAS CLOSED UP A BIT AS CIRRUS
BEGAN OBSCURING THE EYE AND THE INNER CORE CONVECTION CLOSED IN.
THE CENTER I LOCATED ABOUT 30 NM OFF THE NE TIP OF JAMAICA WITH
NUMEROUS STRONG CONVECTION EXTENDING OUT ABOUT 75 NM OF THE
CENTER. A SPIRAL BAND OF SCATTERED MODERATE/STRONG ALSO EXTENDS
AROUND THE E AND S SIDE OF THE HURRICANE ELSEWHERE FROM 14N-21N
BETWEEN 71W-78W. HEAVY FLOODING RAINS HAVE BEEN PUMMELING PARTS
OF HAITI SINCE DENNIS APPROACHED YESTERDAY AND THIS IS EXPECTED
TO CONTINUE UNTIL THE OUTER BAND SHIFTS W LATER TONIGHT. HEAVY
RAINS ACCOMPANIED BY STRONG WINDS TO HURRICANE FORCE ARE ALSO
BEGINNING TO SPREAD OVER JAMAICA...AND THEN INTO SE CUBA LATER
TODAY.

...TROPICAL WAVES...

LOW PRES CENTERED ALONG THE ITCZ S OF THE CAPE VERDES APPEARS TO
HAVE DISSIPATED AT THE SURFACE...REMAINING AS A BROAD MID-LEVEL
CIRCULATION WHICH DEVELOPED FROM STRONG CONVECTION MOVING OFF
THE AFRICAN COAST YESTERDAY. QUIKSCAT IMAGERY FROM THIS MORNING
SHOWED FAIRLY STRONG 20-25 KT SWLY FLOW NEAR THE ALLEGED
CENTER...AND THIS FEATURE APPEARS TO BE ASSOCIATED WITH A
LOW-LEVEL PERTURBATION WHICH PASSED DAKAR YESTERDAY. IT LOOKS
LIKE A DEEP-LAYERED TROPICAL WAVE IS JUST ABOUT TO MOVE OFF THE
COAST SINCE THE WINDS HAD A STRONG N/NW COMPONENT IN THE DAKAR
SOUNDING FROM THIS MORNING. THIS AREA WILL BE MONITORED TO SEE
IF THESE TWO SEPARATE FEATURES CONSOLIDATE OVER THE NEXT FEW
DAYS. CONVECTION IS ALIGNED ALONG THE ITCZ.

EAST ATLANTIC TROPICAL WAVE ALONG 5N36W 23N32W MOVING W 10-15
KT. VISIBLE IMAGERY INDICATES A FAINT NOTCH IN THE STRATOCU
FIELD ALONG 35W/36W AND A NWD SURGE OF SAHARAN DUST TO THE E OF
THE AXIS. THIS POSITION MATCHES WELL WITH THE GFS 700 MB
WIND/VORTICITY FIELD. WIDELY SCATTERED MODERATE CONVECTION FROM
8N-11N BETWEEN 33W-35W.

CENTRAL ATLANTIC TROPICAL WAVE ALONG 55W S OF 20N MOVING W 15
KT. THE CAYENNE UPPER AIR SOUNDING SHOWS A WELL-DEFINED WAVE
PASSAGE DURING THE NIGHT...SO IT SEEMS WE FINALLY HAVE A BETTER
HANDLE ON ITS POSITION. IT ALSO HELPS THAT SCATTERED MODERATE
CONVECTION HAS BROKEN OUT N OF THE GUIANAS FROM 6N-12N BETWEEN
53W-60W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 20N13W 14N17W 4N40W 5N54W. WIDELY
SCATTERED MODERATE CONVECTION WITHIN 150 NM N AND 250 NM S OF
THE AXIS BETWEEN 20W-32W. WIDELY SCATTERED MODERATE 180 NM N OF
THE AXIS BETWEEN 37W-47W.

...DISCUSSION...

GULF OF MEXICO...
SFC HIGH PRES CENTERED OVER THE CNTRL GULF AND DRY AIR ALOFT
ASSOCIATED WITH A SHORTWAVE TROF MOVING OFF THE TEXAS COAST ARE
PROVIDING A CLEAR AND ALMOST CLOUDLESS DAY OVER THE REGION. AN
OUTFLOW BOUNDARY WHICH MOVED OFF THE TEXAS/LOUISIANA COAST THIS
MORNING IS PRODUCING SCATTERED SHOWERS/TSTMS WITHIN 120 NM OF
THE COAST BETWEEN 91W-95W BUT SHOULD FIZZLE LATER THIS
AFTERNOON. IN ADDITION...ISOLATED SHOWERS HAVE DECREASED IN
COVERAGE AND INTENSITY ALONG THE SFC TROF TRAILING SW FROM T.D.
CINDY ALONG 30N85W 26N90W. CONDITIONS WILL BEGIN TO DETERIORATE
OVER THE SE GULF ON FRI AS WINDS INCREASE TO TROPICAL STORM
STRENGTH DURING THE AFTERNOON WITH NUMEROUS SHOWERS/TSTMS
SPIRALING FROM E TO W IN THE OUTER SQUALLS OF HURRICANE DENNIS.
HURRICANE CONDITIONS ARE EXPECTED TO SPREAD ACROSS THE E/CNTRL
GULF WATERS FRI EVENING THROUGH SUN...WITH A POTENTIAL LANDFALL
ALONG THE NE/CNTRL GULF COAST.

CARIBBEAN...
SEE SPECIAL FEATURES FOR DISCUSSION ON HURRICANE DENNIS. AN
UPPER LEVEL RIDGE HAS BUILT TO THE E OF DENNIS OVER THE E
CARIBBEAN AS HIGH LEVEL CIRRUS SPREADS FROM NW TO SE OVER THE
NRN LEEWARD ISLANDS. MOISTURE IS RELATIVELY SCARCE E OF ABOUT
70W AS DRY SAHARAN AIR HAS SPREAD W OF THE LESSER ANTILLES IN
THE WAKE OF DENNIS. CURRENTLY ONLY ISOLATED TSTMS ARE LOCATED
ABOUT 150 NM NE OF BONAIRE...BUT MORE SCATTERED CONVECTION WILL
BEGIN TO SPREAD OVER THE WINDWARD ISLANDS TONIGHT WITH THE
APPROACH OF A TROPICAL WAVE. DRY CONDITIONS ALSO EXTEND OUT
AHEAD OF DENNIS OVER THE NW CARIBBEAN WITH A FEW MORE HIGH
CLOUDS OVER THE SW CARIBBEAN DUE TO A STRONG OUTFLOW JET
EMANATING AWAY FROM THE HURRICANE. A SMALL AREA OF SCATTERED
SHOWERS/TSTMS HAVE DEVELOPED WITHIN 90 NM OF THE NICARAGUAN
COAST ALONG A LOW-LEVEL CONVERGENCE LINE.

ATLANTIC...
A WEAK UPPER LOW HAS DEVELOPED NEAR 30N66W FROM THE SHORTWAVE
TROF WHICH DUG S OF BERMUDA YESTERDAY...AND THE NEARLY
STATIONARY MOVEMENT HAS CAUSED THE ASSOCIATED FRONTAL BOUNDARY
TO BECOME STATIONARY ALONG 32N54W 26N64W. SCATTERED MODERATE
CONVECTION IS S OF THE FRONT FROM 26N-29N BETWEEN 56W-61W. THE
REST OF THE W ATLC IS DRY UNDER THE SUBSIDENCE SURROUNDING
HURRICANE DENNIS IN THE CARIBBEAN...BUT WINDS HAVE INCREASED
NEAR THE SRN BAHAMAS WITH THE POTENTIAL FOR TROPICAL STORM FORCE
WINDS AND NUMEROUS SQUALLS TO DEVELOP OVER THE SRN BAHAMAS AND W
OF THE BAHAMAS TONIGHT THROUGH SAT. FARTHER E...A MID-OCEANIC
UPPER LOW IS CENTERED 500 NM NE OF THE NRN LEEWARD ISLANDS NEAR
22N55W BUT IS SURROUNDED BY EXTENSIVE DRY AIR AND IS CAUSING NO
SIGNIFICANT WEATHER. A LARGE UPPER HIGH IS CENTERED OVER THE E
ATLC NEAR 21N26W WITH RIDGE EXTENDING W TO 16N50W. A SWATH OF
DRY SAHARAN AIR AND WIDESPREAD DUST EXTENDS S OF A LINE FROM
25N15W 17N40W 16N50W TO THE ITCZ.

$$
BERG




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