[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 220011
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU JUL 21 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...SPECIAL FEATURE...

TROPICAL STORM FRANKLIN HAS DEVELOPED NEAR 25.8N 76.0W...OR
ABOUT 45 NM ENE OF ELEUTHERA ISLAND IN THE NW BAHAMAS...AT
22/0000 UTC MOVING NW 12 KT. MAXIMUM SUSTAINED WIND SPEED IS 40
KT WITH GUSTS TO 50 KT. ESTIMATED MINIMUM CENTRAL PRESSURE
REPORTED BY AIR FORCE RECONNAISSANCE IS 1009 MB. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
AND THE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31
KNHC FOR MORE DETAILS. FRANKLIN WAS UPGRADED FROM A TROPICAL
DISTURBANCE TO TROPICAL DEPRESSION SIX AT 21/2100 UTC BUT MORE
RECENTLY AIR FORCE RECONNAISSANCE HAS FOUND WINDS STRONG ENOUGH
TO CLASSIFY THE SYSTEM AS A TROPICAL STORM. FRANKLIN IS
RELATIVELY TINY WITH THE CORE OF THE CLOUDS/CONVECTION EXTENDING
NO MORE THAN 100 NM FROM THE CENTER. STRONG CONVECTION HAD BEEN
WRAPPED ENTIRELY AROUND THE SYSTEM EARLIER IN THE DAY...WHICH
PRODUCED AN EYE-LIKE "SUCKER HOLE"...BUT THE TSTMS ARE NOW
FAVORING THE ERN SEMICIRCLE WITH SCATTERED MODERATE FROM 23N-27N
BETWEEN 74W-76W. MORE RECENTLY...A BURST OF TSTMS HAS DEVELOPED
RIGHT NEAR THE CENTER WHICH MAY SOON INITIATE SOME DEEPENING OF
THE SYSTEM. WINDS ARE RELATIVELY LIGHT ON THE WRN SIDE NEAR THE
BAHAMAS...BUT SHOWERS/TSTMS IN SPIRAL BANDS ARE BRUSHING ACROSS
THE ISLANDS OF RUM CAY...SAN SALVADOR...CAT ISLAND...
ELEUTHERA...AND ABACO ISLAND.

...TROPICAL WAVES...

EAST ATLANTIC TROPICAL WAVE ALONG 28W/29W S OF 26N MOVING W
15-20 KT WITH A BROAD 1010 MB LOW CENTERED NEAR 13N29W. THE LOW
CENTER HAS BEEN MOVING SW AT ABOUT 18 KT AND APPEARS TO BE
BECOMING MORE DIFFUSE AS IT NEARS THE ITCZ. THE WAVE CONTINUES
TO CARRY A LARGE ENVELOPE OF SAHARAN DUST WWD ACROSS THE ATLC
AND THE DRY AIR HAS SQUELCHED ANY DEEP CONVECTION NEAR THE MAIN
PART OF THE WAVE. LOW-LEVEL STRATUS/STRATOCU ARE FROM 13N-22N
BETWEEN 27W-38W AND BROKEN MID-LEVEL CLOUDS HAVE DEVELOPED NEAR
THE APEX OF THE WAVE FROM 23N-28N BETWEEN 23W-31W. DEEPER
MOISTURE IS CURRENTLY LOCATED ON THE BACK SIDE OF THE WAVE
BETWEEN AFRICA AND THE CAPE VERDES...AND WILL CONTINUE SHIFTING
WWD OVER THE ISLANDS TONIGHT AND ON FRI WITH WIDELY SCATTERED
SHOWERS.

CENTRAL ATLANTIC TROPICAL WAVE BENT ALONG 8N52W 15N51W 22N48W
MOVING W 15-20 KT. THE CLASSIC INVERTED-V SIGNATURE HAS BEEN
SOLIDLY MAINTAINED WITH THIS WAVE FOR THE PAST FEW DAYS...AND
APPEARS TO LIE ALONG THE LEADING EDGE OF THE STRONG DUST SURGE
TO THE E. ONLY ISOLATED SHOWERS/TSTMS ARE LOCATED W OF THE WAVE
AXIS FROM 11N-16N BETWEEN 54W-58W...AND WIDESPREAD CONVECTION IS
NOT EXPECTED TO AFFECT THE LESSER ANTILLES AS THE WAVE PASSES
FRI AND SAT.

WEAK TROPICAL WAVE OVER THE SRN CARIBBEAN ALONG 69W S OF 13N
MOVING W 15-20 KT. WEATHER OVER THE ABC ISLANDS REMAINS TRANQUIL
BUT SCATTERED MODERATE CONVECTION HAS DEVELOPED FARTHER S OVER
VENEZUELA FROM 6N-10N BETWEEN 64W-71W.

STRONG WEST CARIBBEAN TROPICAL WAVE EXTENDS FROM W/CNTRL CUBA TO
THE NICARAGUA COAST ROUGHLY ALONG 83W/84W MOVING W NEAR 20 KT.
THE AREA OF STRONG CONVECTION THAT WAS LOCATED OVER THE SW
CARIBBEAN YESTERDAY HAS SHIFTED N/NW WITH THE APPROACH OF THE
WAVE...AND HAS MOVED BENEATH A STRONG UPPER LEVEL ANTICYCLONE
CENTERED NEAR THE CAYMAN ISLANDS. THIS HAS SUPPORTED A LARGE
CLUSTER OF NUMEROUS MODERATE CONVECTION FROM 15N-23N BETWEEN
78W-85W WHICH ARE BRUSHING THE WRN EDGE OF JAMAICA AND SPREADING
NWD OVER THE CAYMAN ISLANDS AND CUBA. SCATTERED MODERATE ALSO
EXTENDS FARTHER S FROM 11N-15N BETWEEN 79W-82W AS WELL AS OVER
PARTS OF HONDURAS AND NICARAGUA. THERE IS NO INDICATION OF A SFC
LOW DEVELOPING AT THE MOMENT...BUT THE ISOBARIC ANALYSIS
SUGGESTS THAT THE WAVE IS BECOMING SHARPER AND A LOW COULD FORM
TONIGHT OR ON FRI. HEAVY RAINFALL IS EXPECTED TO BEGIN SPREADING
OVER BELIZE AND THE YUCATAN PENINSULA LATER TONIGHT AND THEN
INTO THE SW GULF OF MEXICO LATE FRI.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 13N13W 20N24W...THEN ALONG 16N23W
10N29W 7N42W 13N52W...THEN ALONG 11N54W 8N68W 11N80W. NUMEROUS
STRONG CONVECTION OVER SW MAURITANIA...WRN GUINEA...AND SIERRA
LEONE. SCATTERED MODERATE WITHIN 60 NM OF THE AXIS BETWEEN
24W-34W. WIDELY SCATTERED MODERATE WITHIN 75 NM OF THE AXIS
BETWEEN 44W-53W. SCATTERED MODERATE ALONG THE COAST OF COLOMBIA
NEAR BARRANQUILLA AND CARTAGENA.

...DISCUSSION...

GULF OF MEXICO...
THE GULF WATERS ARE ENJOYING A RELATIVELY BENIGN WEATHER PATTERN
THIS EVENING BEFORE SHOWERS/TSTMS BEGIN TO INCREASE FROM THE SE
TONIGHT AND TOMORROW. THE REMNANTS OF EMILY HAVE MOVED ENTIRELY
INTO NRN MEXICO WITH THE MID-LEVEL CENTER LOCATED ABOUT 150 NM
SSE OF CHIHUAHUA. A SHARP MID/UPPER TROF LIES OVER THE ERN BAY
OF CAMPECHE AND IS MOVING W AS THE LEADING EDGE OF A LARGE SLUG
OF MOISTURE CURRENTLY OVER THE NW CARIBBEAN. FOR THE TIME
BEING...HOWEVER...A LARGE AREA OF DRY AIR EXTENDS N AND W OF
THIS TROF AND IS KEEPING SKIES MAINLY CLEAR OVER THE SW...NW...
AND NE GULF. ISOLATED SHOWERS/TSTMS HAVE BEGUN TO DEVELOP OVER
THE SE GULF S OF 26N E OF 90W...AS WELL AS SCATTERED MODERATE
DAYTIME CONVECTION OVER THE YUCATAN PENINSULA.

CARIBBEAN...
SEE TROPICAL WAVES FOR THE LARGE AREA OF CONVECTION OVER THE NW
CARIBBEAN. ELSEWHERE...E/NE UPPER LEVEL FLOW OVER THE E
CARIBBEAN IS ADVECTING A MODEST AREA OF STRONG SUBSIDENCE OVER
AND TO THE W OF THE LESSER ANTILLES AND IS PRODUCING PLEASANT
WEATHER E OF 77W. CIRRUS OUTFLOW FROM THE NW CARIBBEAN
CONVECTION IS BEING PICKED UP BY NLY FLOW AND IS BEING SPREAD
SWD OVER THE CNTRL CARIBBEAN TO THE N COAST OF COLOMBIA.
MOISTURE CONTINUES TO LINGER OVER HISPANIOLA AND THE WINDWARD
PASSAGE AS TROPICAL STORM FRANKLIN MOVES TO THE N WHICH IS
SUPPORTING ISOLATED SHOWERS ESPECIALLY OVER THE MOUNTAINOUS
TERRAIN.

WEST/CENTRAL ATLANTIC...
TROPICAL STORM FRANKLIN HAS FORMED OVER THE FAR W ATLC NEAR THE
NRN BAHAMAS AND IS OVERLAIN BY A RATHER SMALL UPPER LEVEL
HIGH/RIDGE ALONG 28N77W 19N68W WHICH IS KEEPING MOST OF THE
CLOUDINESS CONFINED TO W OF 70W. SEE SPECIAL FEATURES FOR MORE
ON T.S. FRANKLIN. THE SUBTROPICAL RIDGE REMAINS ANCHORED OVER
THE CNTRL ATLC ALONG 26N WITH A 1022 MB HIGH NEAR 27N66W. THE
UPPER LEVEL MID-OCEANIC TROF SNAKES ACROSS THE AREA FROM 30N40W
26N50W 21N55W 25N65W AND IS PRODUCING ENOUGH SUBSIDENCE OVER THE
HIGH TO KEEP THE REGION BETWEEN 40W-70W MAINLY CLEAR. A FEW
MID/HIGH CLOUDS ARE SKIRTING THE AREA N OF 28N BETWEEN 52W-70W
AS A SHORTWAVE MOVES QUICKLY EWD ACROSS THE NW ATLC WATERS. A
TRPCL WAVE IS APPROACHING THE LESSER ANTILLES...ABOUT 500 NM TO
THE E...BUT LIMITED MOISTURE IS REALLY SUBDUING DEEP CONVECTION.

EAST ATLANTIC...
WIDESPREAD DUST COVERS A GOOD CHUNK OF THE E ATLC...ESSENTIALLY
EVERYWHERE N OF THE ITCZ TO A LINE FROM MADEIRA ISLAND SW TO
23N50W. VISIBILITY AT SAL IN THE CAPE VERDES HAS IMPROVED
THROUGH THE DAY TO ABOUT 7 MILES AS THE MOST CONCENTRATED DUST
SHIFTS TO THE W WITH THE TRPCL WAVE. A STRONG UPPER LEVEL HIGH
IS CENTERED NW OF THE ISLANDS NEAR 20N32W AND IS CAPPING THE
ENVIRONMENT TO KEEP THE DUST TRAPPED IN THE LOW/MID LEVELS.
HOWEVER...DEEPER MOISTURE IS LOCATED E OF 27W AND IS MOVING TO
THE W WHICH SHOULD PARTIALLY IMPROVE CONDITIONS.

$$
BERG







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