[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 241209
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN JUL 24 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...SPECIAL FEATURES...

TROPICAL STORM GERT AND IS CENTERED NEAR 21.1N 95.8W AT 24/1200
UTC MOVING WNW AT 9 KT. MAXIMUM SUSTAINED WIND SPEED IS 35 KT
WITH GUSTS TO 45 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009
MB. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT2/WTNT22 KNHC AND THE PUBLIC ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. NOAA RESEARCH
AIRCRAFT PREVIOUSLY FOUND A NEW LOW LEVEL CENTER 60 NM N OF THE
PREVIOUS CENTER...HOWEVER LATEST RECONNAISSANCE DATA SUGGESTS
THAT THE CENTER IS BROAD AND POORLY-DEFINED. NUMEROUS STRONG
CONVECTION IS EXPANDING AROUND THE CENTER...AND IS NOW WITHIN
150 NM IN THE S QUADRANT...120 NM IN THE N QUADRANT...AND WITHIN
60-90 NM ELSEWHERE. SOME FURTHER INTENSIFICATION IS EXPECTED...
BUT IT REMAINS UNLIKELY THAT GERT WILL MAKE HURRICANE BEFORE
LANDFALL ALONG THE CENTRAL MEXICAN COAST LATER TODAY INTO MON
MORNING.

TROPICAL STORM FRANKLIN IS CENTERED NEAR 30.5N 72.3W AT 24/0900
UTC MOVING ENE AT 8 KT. MAXIMUM SUSTAINED WIND SPEED IS 55 KT
WITH GUSTS TO 65 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002
MB. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. NW SHEAR REMAINS OVER
FRANKLIN BUT LITTLE CHANGE IN INTENSIFICATION IS INDICATED.
SATELLITE IMAGERY SHOWS A PARTIALLY EXPOSED LOW LEVEL
CENTER...INDICATION OF POSSIBLE WEAKENING. CONVECTION IS
DISPLACED TO THE S AND W WITH SCATTERED MODERATE/ISOLATED STRONG
CONVECTION WITHIN 60/75 NM OF LINE FROM 31N71W SW ALONG 27N74W
THEN WNW TO 28N79W. THE FORECAST TRACK TAKES FRANKLIN NW OF
BERMUDA ON TUE INTO WED.

...TROPICAL WAVES...

FAR E ATLC TROPICAL WAVE IS ALONG 23W/24W S OF 16N MOVING W
10-15 KT. BROAD MID LEVEL TURNING IS OBSERVED ON VISIBLE
SATELLITE IMAGERY. CONVECTION IS CONFINED TO WITH THE ITCZ.

CENTRAL ATLC TROPICAL WAVE IS FROM 22N47W THROUGH A 1011 MB LOW
NEAR 11N50W TO 7N51W MOVING W 15-20 KT. WELL-DEFINED...
PERSISTENT BROAD CURVATURE IS OBSERVED ON INFRARED SATELLITE
IMAGERY WITH A WEAK LOW LEVEL CIRCULATION. WAVE REMAINS EMBEDDED
BROAD AREA OF AFRICAN DUST COUPLED WITH DRY AIR ARE LIMITING
DEEP CONVECTION.

CENTRAL CARIBBEAN TROPICAL WAVE IS ALONG 75W/76W S OF 20N MOVING
W 15-20 KT. THIS WAVE MARKS THE LEADING EDGE OF THE AFRICAN DUST
SURGE...BUT THE CONCENTRATIONS APPEAR THINER AS IT MOVES ACROSS
THE CARIBBEAN. SCATTERED MODERATE/STRONG CONVECTION IS W OF THE
WAVE AXIS S OF 11N FROM 76W-78.5W TO INLAND OVER N COLOMBIA AND
THE COAST OF PANAMA.

SW CARIBBEAN TROPICAL WAVE IS ALONG 82W/83W S OF 15N MOVING W
10-15 KT. THE WAVE CONTINUES TO HAVE A POOR SIGNATURE BUT IS
STILL TRIGGERING SCATTERED MODERATE/STRONG CONVECTION INLAND AND
WITHIN 60 NM ALONG THE COAST OF NICARAGUA AND COSTA RICA S OF
13N W OF 82W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 14N16W 12N21W 10N28W 12N38W 13N48W
...THEN ALONG 11N53W 10N57W 11N64W. SCATTERED MODERATE/STRONG
CONVECTION IS WITHIN 200 NM OF N OF THE AXIS FROM 56W-60W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-11N
BETWEEN 29W-34W. CLUSTERS OF SIMILAR CONVECTION ARE WITHIN 180
NM OF THE AXIS FROM 20W-29W. CLUSTERS OF SCATTERED MODERATE
CONVECTION ARE WELL S OF THE AXIS FROM 1N-7N BETWEEN 34W-46W.

...DISCUSSION...

GULF OF MEXICO...
MID/UPPER HIGH IS LOCATED OVER THE SW GULF NE OF T.S. GERT NEAR
22N92W WITH A RIDGE EXTENDING N OFF THE COAST OF MEXICO TO
INLAND OVER TEXAS GIVING THE FAR NW GULF CLEAR WEATHER.
MID/UPPER LOW OFF THE SE COAST OF FLORIDA NEAR 25N81W COVERS THE
E GULF E OF 89W TO JUST OVER FLORIDA. ASSOCIATED SURFACE TROUGH
EXTENDS ACROSS N FLORIDA NEAR 29N83W ALONG 29N86W TO INLAND OVER
LOUISIANA NEAR 30N90W. DIFFLUENCE OVER THE N GULF COAST AND THE
SURFACE TROUGH ARE GENERATING CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION N OF 27N E OF 89W. ALSO AT
THE SURFACE...A WEAK 1019 MB HIGH IS OVER THE NORTH CENTRAL GULF
NEAR 27N88W.

CARIBBEAN...
WATER VAPOR IMAGERY SHOWS VERY LITTLE DEEP MOISTURE OVER THE
CARIBBEAN AT THE MOMENT WITH ONLY SHOWERS/CONVECTION ASSOCIATED
WITH THE TROPICAL WAVES. DRY AIR WITH SUSPENDED AFRICAN DUST HAS
MOVED INTO THE CENTRAL CARIBBEAN ESSENTIALLY PRECLUDING THE
DEVELOPMENT OF DEEP CONVECTION. THE DUST CAN PRODUCE HAZY SKIES
OVER THE AREA AS IT CONTINUES MARCHING WEST.

ATLANTIC...
MID/UPPER LOW IS OFF THE SE COAST OF FLORIDA NEAR 25N81W COVERS
THE W ATLC W OF 79W INTO THE GULF OF MEXICO. A MID/UPPER LEVEL
HIGH IS CENTERED SW OF FRANKLIN 28N75W WITH RIDGE EXTENDING E TO
28N67W. ANTICYCLONIC FLOW COVERS THE AREA N OF 20N FROM 68W-79W.
THIS HIGH/RIDGE BUTTS UP AGAINST THE NARROWING MID-OCEANIC
TROUGH WHICH LIES ALONG 30N47W TO A WEAK UPPER LOW NEAR 24N57W
TO A SECOND UPPER LOW N OF HISPANIOLA NEAR 20N69W. SURFACE
TROUGH LIES ALONG 32N57W TO 27N61W AND IS PRODUCING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS WITHIN 175 NM OF LINE 27N60W TO
BEYOND 32N54W...BUT THE NE SHEAR IS PROHIBITING ANY ORGANIZED
ACTIVITY. ALTHOUGH THE W ATLC THROUGH THE CENTRAL CARIBBEAN IS
UNDER STRONG SUBSIDENCE...COUPLED WITH THE DRY AIR/AFRICAN DUST
ESSENTIALLY HAVE CAPPED THE AREA LIMITING MOST OF THE SHOWER
ACTIVITY. THE BACK END OF THE MOST CONCENTRATED DUST IS NEAR 38W
BUT A LESS DENSE AREA OF DUST HAS MOVED OFF AFRICA LINGERING N
OF THE CAPE VERDE ISLANDS. FARTHER S...DEEP EASTERLY FLOW
EXTENDS ACROSS THE E/CNTRL ATLC S OF 16N WITH JUST ENOUGH UPPER
DIFFLUENCE CENTERED OVER THE ITCZ TO SUPPORT SOME AREAS OF
CONVECTION.

$$
WALLACE



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