[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 241800
TWDAT

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

...SPECIAL FEATURES...

TROPICAL STORM GERT IS CENTERED NEAR 21.4N 96.6W AT 24/1800 UTC
OR ABOUT 90 NM SE OF TAMPICO MEXICO MOVING WNW AT 8 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. AIR FORCE HURRICANE HUNTERS WERE UNABLE
TO LOCATE A DEFINITE CENTER THIS MORNING...WHICH SUPPORTS THE
SATELLITE PRESENTATION OF A BROAD AND ELONGATED SYSTEM ORIENTED
NNW-SSE. CONVECTION HAS INTENSIFIED...WITH NUMEROUS
MODERATE/STRONG CONVECTION IN BANDS EXTENDING ALONG AND JUST OFF
THE MEXICAN COAST FROM COATZACOALCOS NORTH TO NEAR 25N. UPPER
LEVEL HIGH OVER THE NW GULF OF MEXICO IS PROVIDING FOR GOOD
OUTFLOW IN ALL QUADRANTS... AND THE SYSTEM HAS THE POTENTIAL FOR
STRENGTHENING BEFORE MAKING LANDFALL ALONG THE E COAST OF
MEXICO...LATER TODAY OR THIS EVENING...ESPECIALLY IF THE CENTER
CONSOLIDATES BEFORE LANDFALL.

TROPICAL STORM FRANKLIN IS CENTERED NEAR 30.9N 71.4W AT 24/1500
UTC MOVING ENE AT 9 KT. MAXIMUM SUSTAINED WIND SPEED IS 55 KT
WITH GUSTS TO 65 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1001
MB. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. NORTHERLY SHEAR
CONTINUES TO TAKE ITS TOLL ON FRANKLIN AS SATELLITE IMAGES
REVEAL A FULLY-EXPOSED LOW-LEVEL CIRCULATION N OF THE MAIN
CLUSTER OF DEEP CONVECTION WHICH EXTENDS TO 150 NM IN THE SE AND
S QUADRANTS FROM THE CENTER. A BROKEN BAND OF SCATTERED
SHOWERS/TSTMS EXTENDING WELL SW FROM THE CENTER FROM 27.5N72W-
27N76W TO JUST N OF THE NW BAHAMAS AND E OF FLORIDA COAST IS
ASSOCIATED WITH A WEAK SURFACE LOW AND TROUGH NOT DIRECTLY
ASSOCIATED WITH THE TROPICAL STORM. WATER VAPOR IMAGERY
INDICATES NORTHERLY UPPER LEVEL FLOW OF 30-50 KT MOVING OFF THE
COAST OF THE CAROLINAS IMPINGING ON FRANKLIN. FURTHER WEAKENING
IS EXPECTED AS THE STORM MOVES NE AND CONTINUES UNDER NORTHERLY
SHEAR AND COOLER WATER. FRANKLIN IS FORECAST TO PASS JUST NORTH
OF BERMUDA IN ABOUT 48 HOURS.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE IS ALONG 24W/25W S OF 15N MOVING W 10-15
KT. SATELLITE IMAGERY INDICATES THAT A LOW LEVEL CIRCULATION MAY
BE FORMING NEAR 11N25W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION N OF THE POSSIBLE CIRCULATION FROM 11N-13N BETWEEN
25W-27W IS DISORGANIZED AT THE PRESENT TIME. ITCZ CONVECTION TO
THE SW APPEARS TO BE CONNECTED TO THE OVERALL CIRCULATION.
BROKEN/OVERCAST LOW/MID CLOUDS ARE SURGING NORTHWARD ON THE E
SIDE OF THE WAVE AND MOVING OVER THE SOUTHERN CAPE VERDE
ISLANDS. SHOWERS AND TSTMS WILL INCREASE NEAR OR OVER THE ISLAND
CHAIN OVER THE NEXT 24 HOURS AS THE WAVE CONTINUES WESTWARD.

CENTRAL ATLC TROPICAL WAVE FROM 20N50W-13N53W-6N56W MOVING W
NEAR 20 KT. WAVE WAS REPOSITIONED SLIGHTLY TO THE W BASED ON
1200 UTC UPPER AIR DATA FROM GUYANA AND EARLY MORNING QUIKSCAT
DATA. LEADING EDGE OF WAVE IS ABOUT 100-150 NM E OF BARBADOS AND
THE REMAINDER OF THE WINDWARD ISLANDS. CIRCULATION ASSOCIATED
WITH THE WAVE CONTINUES TO BE QUITE BROAD...EXTENDING E TO 45W
AND W TO THE WINDWARD ISLANDS. EARLIER SURFACE LOW HAD
DISSIPATED... ALTHOUGH A LOW-LEVEL CIRCULATION MAY STILL BE
EVIDENT NEAR 12N51W. AN AREA OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS W OF THE AXIS FROM 10N-13N BETWEEN 58W-62W.
THIS CONVECTION WILL AFFECT THE WINDWARD ISLANDS DURING THE NEXT
SEVERAL HOURS AS THE WAVE MOVES THROUGH THE AREA.

W CARIBBEAN TROPICAL WAVE FROM SE COAST OF CUBA TO ACROSS
JAMAICA ALONG 77W/78W S OF 20N MOVING W 20 KT. 1200 UTC UPPER
AIR DATA FROM KINGSTON JAMAICA INDICATED THAT THE WAVE HAD
PASSED THROUGH THE STATION DURING THE OVERNIGHT HOURS. WIDELY
SCATTERED MODERATE CONVECTION IS N OF 15N WITHIN 120 NM EITHER
SIDE OF AXIS AS IT APPROACHES THE CAYMAN ISLANDS. THIS WAVE
MARKS THE LEADING EDGE OF THE AFRICAN DUST SURGE...BUT THE
CONCENTRATIONS APPEAR THINER AS IT MOVES ACROSS THE CARIBBEAN.

CENTRAL AMERICA TROPICAL WAVE IS OVER NICARAGUA AND EASTERN
HONDURAS ALONG 84W MOVING W 15-20 KT. SCATTERED MODERATE/STRONG
CONVECTION COVERS MUCH OF NICARAGUA AND EASTERN PORTIONS OF
HONDURAS...WITH ISOLATED CELLS TRAILING BACK OVER SW CARIBBEAN S
OF SAN ANDRES ISLAND.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 13N16W 12N23W 8N28W 10N40W 11N51W
9N61W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM OF THE AXIS
ALONG AND JUST OFF THE AFRICAN COAST NEAR 13N16W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM OF THE AXIS
BETWEEN 29W-38W. ISOLATED MODERATE CONVECTION IS WITHIN 60 NM OF
AXIS BETWEEN 40W-45W.

...DISCUSSION...

GULF OF MEXICO AND FLORIDA...
MID/UPPER HIGH OVER THE NW GULF DOMINATES THE LARGE SCALE
PATTERN ACROSS THE AREA. DIFFLUENT SE FLOW ON THE SW SIDE OF THE
HIGH CONTINUES TO PROVIDE GOOD OUTFLOW OVER TROPICAL STORM GERT.
ANTICYCLONIC FLOW COVERS MOST OF GULF...EXCEPT OVER THE SE GULF
AND S FLORIDA WHERE A SMALL MID/UPPER LEVEL LOW IS OVER THE FAR
SE GULF NEAR THE LOWER KEYS. AT THE SURFACE...HIGH PRES 1019 MB
IS NEAR 28N91W AND LOW PRES 1014 MB IS JUST E OF CAPE CANAVERAL.
A TROUGH EXTENDING W FROM THE LOW ACROSS THE CENTRAL FLORIDA
PENINSULA TO JUST S OF MOBILE NEAR 30N88W. N-NE MID/UPPER FLOW
IS ADVECTING DRIER AIR OVER THE NE GULF AND N FLORIDA PENINSULA.
A WELL DEFINED MOISTURE GRADIENT EXISTS ACROSS CENTRAL FLORIDA
NEAR THE SURFACE TROUGH AXIS...WITH SCATTERED SHOWERS/TSTMS
CONCENTRATED ALONG AND S OF THE BOUNDARY. THE SURFACE LOW AND
TROUGH ARE EXPECTED TO MOVE SLOWLY S OVER THE NEXT 24
HOURS...WITH HIGHER RAIN CHANCES OVER THE SOUTHERN HALF OF
THE FLORIDA PENINSULA.

CARIBBEAN...
WATER VAPOR IMAGERY SHOWS VERY LITTLE DEEP MOISTURE OVER MOST OF
THE CARIBBEAN WITH ONLY SHOWERS/CONVECTION ASSOCIATED WITH THE
TROPICAL WAVES. DRY AIR WITH SUSPENDED AFRICAN DUST IS SPREADING
W INTO THE WESTERN CARIBBEAN. MAIN UPPER LEVEL FEATURE IS A
TROUGH AXIS EXTENDING FROM THE EASTERN DOMINICAN REPUBLIC TO THE
SW CARIBBEAN NEAR 11N79W. THE TROUGH DIVIDES NE FLOW OVER THE W
CARIBBEAN FROM SW FLOW OVER THE CENTRAL/E CARIBBEAN. SHOWERS AND
TSTMS WILL SPREAD OVER THE FAR SE CARIBBEAN OVER THE NEXT 24
HOURS AS THE WAVE APPROACHING THE ISLANDS MOVES INTO THE REGION.

ATLANTIC...
MID/UPPER LEVEL TROUGH MOVING SE EXTENDS FROM 32N68W TO THE NE
FLORIDA COAST NEAR 30N81W. NORTHERLY FLOW N OF THE TROUGH IS
PRODUCING THE SHEAR AND RESULTING HOSTILE ENVIRONMENT OVER
TROPICAL STORM FRANKLIN. REST OF WESTERN ATLANTIC IS DOMINATED
BY DEEP LAYERED HIGH PRESSURE AND SUBSIDENCE ALOFT. NARROW
MID-OCEANIC TROUGH LIES ALONG 32N51W-23N58W...WITH SMALL
CYCLONIC CIRCULATION JUST N OF DOMINICAN REPUBLIC NEAR 20N69W
SPLITTING OFF FROM THE TROUGH. WEAK LOW LEVEL CONVERGENCE N OF
RIDGE AXIS FROM 32N35W-26N53W-24N70W IS INTERACTING WITH THE
UPPER TROUGH TO PRODUCE SCATTERED MODERATE CONVECTION WITHIN 60
NM OF LINE 32N51W-27N58W. EASTERN ATLANTIC IS DOMINATED BY RIDGE
ALOFT ALONG 16N...WITH MAIN HIGH CENTER NEAR 14N54W. DIFFLUENCE
SW OF THE HIGH CENTER IS AIDING IN DEVELOPMENT OF CONVECTION W
OF WAVE APPROACHING THE WINDWARD ISLANDS. DEEP EASTERLY FLOW S
OF THE RIDGE HAS ENOUGH UPPER DIFFLUENCE AND AVAILABLE MOISTURE
TO SUPPORT CONVECTION NEAR THE ITCZ AND E ATLC TROPICAL WAVE.
LARGE AREA OF SAHARAN DUST COVERS MOST OF EASTERN ATLANTIC...
WITH MAIN CONCENTRATIONS S OF 23N W OF 40W AND N OF 17N E OF 40W
TO THE AFRICAN COAST.

$$
MOLLEDA


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