[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 231809
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT JUL 23 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 FRANKLIN IS CENTERED NEAR 29.4N 75.0W...OR ABOUT
550 NM SSW OF BERMUDA...AT 23/1500 UTC MOVING NE 8 KT. MAXIMUM
SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT.  ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1001 MB. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE
DETAILS. FRANKLIN HAS BECOME BETTER ORGANIZED IN THE LAST
SEVERAL HOURS WITH BANDING FEATURES MORE PRONOUNCED IN THE S AND
SW QUADRANTS. THE LOW LEVEL CIRCULATION APPEARS TO HAVE
TIGHTENED UP ON HIGH RESOLUTION SATELLITE IMAGERY...WITH THE
CENTER LOCATED NEAR THE N EDGE OF THE CENTRAL DENSE OVERCAST
REGION. UPPER LEVEL OUTFLOW REMAINS GOOD IN THE ERN
SEMICIRCLE...BUT RESTRICTED ELSEWHERE...PARTICULARLY IN THE N
QUADRANT...DUE TO NORTHERLY FLOW ON THE BACK SIDE OF A MID/UPPER
LEVEL TROUGH MOVING OFF THE EASTERN U.S. SEABOARD. NUMEROUS
MODERATE TO STRONG CONVECTION IS WITHIN 120-150 NM OF THE CENTER
IN THE S SEMICIRCLE.

A STRONG TROPICAL WAVE IN THE GULF OF MEXICO ALONG 92W/93W HAS A
SURFACE LOW NEAR 19.5N93W 1012 MB...MOVING WNW 10-15 KT. HIGH
RESOLUTION SATELLITE IMAGERY INDICATES A WELL-DEFINED LOW LEVEL
CIRCULATION WITH A SMALL CLUSTER OF MODERATE CONVECTION JUST NW
OF THE LOW. FARTHER W...A LINE OF SCATTERED MODERATE CONVECTION
MAY BE DEVELOPING INTO A BROAD CURVED BAND WITHIN 30 NM OF THE
EAST COAST OF MEXICO FROM S OF TAMPICO SWD TO COATZACOALCOS.
SYSTEM IS UNDERNEATH UPPER LEVEL SE-S WINDS OF 15-25
KT...HOWEVER CONDITIONS ARE FAVORABLE FOR TROPICAL CYCLONE
DEVELOPMENT DURING THE NEXT 24 HOURS AS THE LOW MOVES WNW
UNDERNEATH STRONGER UPPER LEVEL DIFFLUENCE NEAR THE EAST COAST
OF MEXICO.

...TROPICAL WAVES...

EAST ATLANTIC TROPICAL WAVE ALONG 42W/43W S OF 22N MOVING W
15-20 KT. EARLY MORNING QUIKSCAT DATA AND SATELLITE IMAGERY
INDICATE THAT A SURFACE LOW IS ALONG THE WAVE NEAR 11N43W 1012
MB. WAVE REMAINS LARGE IN AMPLITUDE AND EMBEDDED IN AN AREA OF
DUST. WATER VAPOR IMAGERY INDICATES SUBSIDENCE AND DRY AIR ALONG
AND W OF THE WAVE...KEEPING DEEP CONVECTION TO A MINIMUM ALONG
AND W OF WAVE. E OF THE WAVE...SLY SURGE OF MOISTURE IS
PRODUCING SCATTERED MODERATE CONVECTION ALONG THE ITCZ BETWEEN
35W-39W.

EAST CARIBBEAN TROPICAL WAVE ALONG 67W/68W S OF 21N MOVING W
15-20 KT. SATELLITE SIGNATURE NOT AS EVIDENT AS 24 HOURS
AGO...HOWEVER 1200 UTC UPPER-AIR SOUNDING AT SAN JUAN INDICATED
A SHIFT IN THE LOW LEVEL WINDS TO THE SE...INDICATIVE OF A WAVE
PASSAGE ACROSS PUERTO RICO THIS MORNING. DUST IS EVIDENT ON
VISIBLE SATELLITE IMAGERY ALONG AND E OF WAVE...ALTHOUGH SURFACE
STATIONS ACROSS THE E CARIBBEAN ARE NOT REPORTING REDUCTIONS IN
VISIBILITIES. ONLY ASSOCIATED DEEP CONVECTION IS A SMALL AREA OF
SHOWERS AND TSTMS ABOUT 90-120 NM N OF PUERTO RICO.

WEAK TROPICAL WAVE ALONG CENTRAL COLOMBIA NEAR 76W/77W S OF 13N
MOVING W 20 KT. LOW-AMPLITUDE WAVE REMAINS DIFFICULT TO LOCATE
ON SATELLITE IMAGERY AND SURFACE OBSERVATIONS...ALTHOUGH SMALL
AREA OF SHOWERS/TSTMS OVER SW CARIBBEAN NEAR 11N78W MAY BE A
POSSIBLE INDICATOR OF WAVE POSITION.

SEE SPECIAL FEATURES FOR DISCUSSION ON TROPICAL WAVE AND LOW
PRESSURE OVER BAY OF CAMPECHE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 11N17W 8N30W 9N39W 7N45W TO 5N53W
OVER GUYANA. SCATTERED MODERATE/ISOLATED STRONG CONVECTION HAS
MOSTLY MOVED OFF THE COAST OF AFRICA AND IS LOCATED WITHIN 120
NM OF AXIS BETWEEN 17W-30W. DISSIPATING SCATTERED MODERATE
CONVECTION IS WITHIN 60 NM OF AXIS BETWEEN 36W-39W...AND WITHIN
30 NM OF AXIS BETWEEN 44W-47W. SCATTERED STRONG CONVECTION S OF
THE ITCZ FROM 2N-4N BETWEEN 38W-40W IS ASSOCIATED WITH A
LOW-LEVEL SURGE OF SE WINDS FROM THE SOUTHERN HEMISPHERE.

...DISCUSSION...

GULF OF MEXICO AND FLORIDA...
LARGE MID/UPPER LEVEL HIGH CENTERED OVER THE SOUTHERN GULF NEAR
22N89W IS CONTROLLING THE FLOW ACROSS THE AREA. THIS IS CAUSING
THE SE-S FLOW ACROSS THE LOW OVER THE BAY OF CAMPECHE. SEE
SPECIAL FEATURES FOR FURTHER DISCUSSION. AT THE SURFACE...A WEAK
AND NEARLY STATIONARY HIGH 1020 MB IS JUST S OF LOUISIANA NEAR
28N91W. NORTHERN EDGE OF PRECIPITATION AREA ASSOCIATED WITH THE
BAY OF CAMPECHE LOW IS NEAR 26N94W...ABOUT 180 NM E OF THE SOUTH
TEXAS COAST. A CLUSTER OF STRONG CONVECTION IS MOVING NW ACROSS
THE YUCATAN PENINSULA...A RESULT OF THE EASTERN END OF THE
CYCLONIC CIRCULATION AND A SURGE OF STRONGER SURFACE SE WINDS
OVER THE FAR W CARIBBEAN SEA. A WEAK LOW LEVEL TROUGH EXTENDS
FROM NEAR THE ALABAMA/MISSISSIPPI COAST ESE TO THE FLORIDA BIG
BEND AND NORTH CENTRAL FLORIDA. ISOLATED SHOWERS/TSTMS ARE ALONG
THIS TROUGH...MOVING SE-S. SHOWERS AND TSTMS ARE MORE NUMEROUS
OVER THE NORTH CENTRAL FLORIDA PENINSULA DUE TO COLD AIR
ALOFT/INSTABILITY FROM A MID/UPPER LOW CENTERED NEAR CAPE
CANAVERAL. THE HIGH WILL SHIFT NW ACROSS THE CENTRAL AND NW GULF
DURING THE NEXT 24 HOURS...WHILE THE MID/UPPER LOW OVER FLORIDA
MOVES S. SHOWERS AND TSTMS WILL SPREAD ACROSS EASTERN MEXICO AND
S TEXAS FROM THE LOW/POSSIBLE TROPICAL CYCLONE...WITH SHOWERS
AND TSTMS ALSO SPREADING SWD OVER THE SOUTHERN HALF OF FLORIDA
AND THE SE GULF.

CARIBBEAN...
DRY AIR IN THE MID/UPPER LEVELS CONTINUES TO SPREAD WESTWARD
ACROSS THE CENTRAL AND W CARIBBEAN DUE TO SUBSIDENCE IN THE NE
FLOW ON THE E SIDE OF THE GULF OF MEXICO MID/UPPER HIGH. WEAK
UPPER LEVEL TROUGH EXTENDS FROM THE DOMINICAN REPUBLIC SW TO A
SMALL CYCLONIC CIRCULATION ON THE NORTHERN COAST OF PANAMA NEAR
10N80W. E OF THE TROUGH...THE FLOW BECOMES MORE DIFFLUENT AS A
RIDGE FROM THE ATLC EXTENDS W INTO THE E CARIBBEAN. SCATTERED
SHOWERS AND TSTMS ARE S OF HISPANIOLA NEAR 17N72W...MOVING W
15-20 KT. HAZY CONDITIONS WILL SPREAD SLOWLY W ACROSS THE
CARIBBEAN AND GREATER ANTILLES DURING THE NEXT FEW DAYS.

WEST ATLANTIC...
TROPICAL STORM FRANKLIN IS MOVING NE AWAY FROM THE NRN BAHAMAS
AND THE SE UNITED STATES COAST AS A MID/UPPER LEVEL LONGWAVE
TROUGH MOVES OFF THE U.S. EASTERN SEABOARD. MID/UPPER LOW NEAR
THE FLORIDA E COAST IS PROVIDING ADDITIONAL OUTFLOW ON THE W
SEMICIRCLE OF FRANKLIN. OTHERWISE...THE WESTERN ATLANTIC IS
DOMINATED BY DEEP LAYERED HIGH PRES WITH A SURFACE RIDGE
EXTENDING FROM 26N60W-25N80W.

CENTRAL/EAST ATLANTIC...
MID-OCEANIC TROUGH EXTENDS FROM 32N48W-22N60W TO THE DOMINICAN
REPUBLIC. WEAK SURFACE TROUGH FROM 30N58W-28N62W IS
INTERACTING WITH A WEAK SHORTWAVE TROUGH JUST N OF AREA TO
PRODUCE SCATTERED SHOWERS/TSTMS WITHIN 60 NM OF THE SURFACE
TROUGH. REST OF CENTRAL AND EASTERN ATLANTIC IS DOMINATED BY
HIGH PRES ALOFT...WITH THE MAIN MID/UPPER LEVEL HIGH CENTERED
NEAR 15N50W...AND A SECOND HIGH LOCATED W OF THE CANARY ISLANDS
NEAR 26N21W. SUBSIDENCE ASSOCIATED WITH HIGH NEAR 15N50W IS
SUPPORTING THE WESTWARD TRANSLATION OF THE SAHARAN DUST LAYER
WHICH IS CONCENTRATED S OF 24N W OF 35W. ANOTHER LAYER OF
DUST IS BETWEEN THE CAPE VERDE AND CANARY ISLANDS ASSOCIATED
WITH THE HIGH W OF THE CANARIES. EASTERLY MID/UPPER LEVEL FLOW S
OF 15N FROM AFRICA TO NEAR 40W IS ADVECTING DEEPER MOISTURE INTO
THE REGION AND SUPPORTING TSTMS ALONG THE ITCZ. UPPER-AIR
SOUNDING DATA FROM DAKAR AND SATELLITE IMAGERY INDICATE THAT A
TROPICAL WAVE MAY HAVE MOVED OFF THE W COAST OF AFRICA LATE LAST
NIGHT. AS A RESULT...A NEW TROPICAL WAVE MAY BE INTRODUCED IN
THE VICINITY OF 20W LATER TODAY OR TONIGHT.

$$
MOLLEDA


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