[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 280604
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU JUL 28 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 0000 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 0515 UTC.

...SPECIAL FEATURE...

TROPICAL STORM FRANKLIN CENTER NEAR 34.3N 69.4W...OR ABOUT
300 MILES/480 KM WEST-NORTHWEST OF BERMUDA...AT 28/0300 UTC
MOVING NORTH 5 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS
1000 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 45 KT GUSTS 55 KT.
SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/ WTNT21 KNHC FOR MORE DETAILS. THE CENTER OF FRANKLIN
IS EXPOSED UNDER THE CIRRUS OUTFLOW. NUMEROUS STRONG SHOWERS AND
THUNDERSTORMS WERE FOUND FROM 32N TO 34N BETWEEN 69W AND
71W AT 27/2345 UTC. THAT PRECIPITATION DIED AND EVERYTHING HAS
RE-DEVELOPED JUST TO THE NORTH FROM 33N TO 35N BETWEEN 68W AND
70W. FRANKLIN STILL HAS ABOUT 24 TO 36 HOURS OF RELATIVELY LIGHT
SHEAR IN ORDER TO INTENSIFY BEFORE AN UPPER TROUGH OVER NORTH
AMERICA BEGINS TO IMPACT STRONG SHEAR ON THE SYSTEM.

...TROPICAL WAVES...

EASTERN ATLANTIC OCEAN TROPICAL WAVE IS ON THE MAP FOR THE FIRST
TIME ALONG 22W/23W SOUTH OF 15N MOVING WEST 15 KT. WIDELY
SCATTERED MODERATE TO ISOLATED STRONG SHOWERS AND THUNDERSTORMS
CURVE FROM 10N23W TO 11N27W TO 9N28W TO 6N27W.

EASTERN ATLANTIC OCEAN TROPICAL WAVE ALONG 33W/34W SOUTH OF 18N
MOVING WEST 15 KT. ISOLATED MODERATE TO LOCALLY STRONG SHOWERS
AND THUNDERSTORMS FROM 7N TO 14N BETWEEN 34W AND 40W.

CENTRAL ATLANTIC TROPICAL WAVE ALONG 21N48W 16N51W TO A 1013 MB
LOW PRESSURE CENTER NEAR 13N52W TO 7N53W...MOVING WEST 20 KT.
NUMEROUS STRONG SHOWERS AND THUNDERSTORMS FROM 17N TO 20N
BETWEEN 47W AND 50W. ISOLATED MODERATE TO LOCALLY STRONG SHOWERS
AND THUNDERSTORMS ELSEWHERE FROM 16N TO 20N BETWEEN 50W AND 55W.
THIS WAVE SHOWS UP QUITE WELL IN SATELLITE IMAGERY. IT MAY
REACH THE EASTERN CARIBBEAN SEA ISLANDS DURING THE NEXT 24 TO
36 HOURS...OR AT LEAST POSSIBLY SOME OF THE SHOWERS TRAVELING
WITH IT MAY REACH THE ISLANDS BEFORE THE ACTUAL WAVE ARRIVES.
THE WAVE CONTINUES TO GAIN PRECIPITATION AS COMPARED TO
YESTERDAY...THOUGH MOST OF IT IS FAR AWAY FROM ANY LOW-LEVEL
CENTER IN THE NORTHERN PART OF THE WAVE ENHANCED BY SHEAR FROM
AN UPPER TROUGH. COMPUTER MODELS SUGGEST THAT THE NORTHERN END
OF THE WAVE EVENTUALLY MAY BECOME THE MORE DOMINANT PART WITH
THE GREATEST POTENTIAL FOR ANY TROPICAL CYCLONE DEVELOPMENT...
THOUGH VERTICAL WIND SHEAR IS MARGINAL. AN INITIAL SURGE OF
MOISTURE IS MOVING THRU THE WINDWARD ISLANDS TONIGHT...WITH
THE MOST SIGNIFICANT MOISTURE TO REACH THE LEEWARD ISLANDS
LATE THURSDAY...OVERSPREADING THE REST OF THE LESSER ANTILLES
ON FRIDAY INTO PUERTO RICO POSSIBLY LATE FRIDAY. THE GFS MODEL
THOUGH SUGGESTS THAT THE HEAVIEST RAINFALL WILL STAY NORTH
OF THE ISLANDS.

WESTERN CARIBBEAN SEA TROPICAL WAVE ALONG 83W SOUTH OF 16N
MOVING WEST ABOUT 20 KT. VERY FAST LOW-LEVEL FLOW AND DRY AIR
ARE MASKING ANY TYPICAL WAVE SIGNALS. ITCZ SHOWERS AND
THUNDERSTORMS OVER LAND AREAS FROM NORTHWESTERN COLOMBIA
TO PANAMA TO THE COASTAL WATERS OF NORTHERN PANAMA TO THE
WATERS NEAR ITS BORDER WITH COSTA RICA.

...THE ITCZ...

ITCZ 13N16W 12N19W 12N22W...11N24W 10N27W 12N32W...11N36W
15N43W 18N48W...9N55W 10N59W. ISOLATED MODERATE SHOWERS...
SOME WEAKENING AND SOME DEVELOPING RECENTLY...FROM 5N TO 9N
BETWEEN 15W AND 23W. SHOWERS AND THUNDERSTORMS FROM 10N TO 12N
BETWEEN 58W AND 59W HAVE BEEN WEAKENING AND/OR HAVE WEAKENED
COMPLETELY DURING THE LAST FEW HOURS. ISOLATED MODERATE SHOWERS
AND LOCALLY STRONG THUNDERSTORMS FROM 1N TO 6N BETWEEN 44W AND
51W IN EXTREME NORTHEASTERN BRAZIL.

...DISCUSSION...

THE GULF OF MEXICO...
ISOLATED MODERATE SHOWERS FROM 24N TO 26N BETWEEN 90S AND THE
COAST OF SOUTH TEXAS/MEXICO...AND FROM 26N TO 28N BETWEEN 84W
AND 93W. MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS
IN INTERIOR NORTHEASTERN MEXICO NEAR 25N101W. BROAD EAST TO
NORTHEAST FLOW ACROSS THE EASTERN GULF WATERS BECOMES CYCLONIC
WITH A MIDDLE TO UPPER LEVEL INVERTED TROUGH WHICH RUNS FROM
THE NORTHWESTERN GULF WATERS TOWARD THE SOUTHWESTERN CORNER OF
THE AREA/YUCATAN PENINSULA. MIDDLE TO UPPER LEVEL DRY AIR IS
IN PLACE PRETTY MUCH EVERYWHERE. 1017 MB SURFACE HIGH PRESSURE
CENTER IS NEAR 24N87W WITH A RIDGE RUNNING FROM IT TOWARD THE
MIDDLE TEXAS COAST. A SURFACE COLD FRONT OVER CENTRAL TEXAS AND
NORTHERN MEXICO WILL APPROACH THE NORTHWESTERN GULF COAST
THROUGHOUT THE REST OF TODAY AND WILL INCREASE THE CHANCE OF
WIDELY SCATTERED SHOWERS AND THUNDERSTORMS IN THE NORTHERN GULF
WATERS THROUGH THE WEEKEND.

THE CARIBBEAN SEA...
MIDDLE TO UPPER LEVEL DRY AIR COVERS MOST OF THE AREA...EXCEPT
FOR THE EXTREME NORTHEASTERN CORNER AND THE EXTREME SOUTHEASTERN
CORNER. MIDDLE TO UPPER LEVEL NORTHEASTERLY WIND FLOW IS PUSHING
SOME UPPER LEVEL MOISTURE INTO THE EXTREME NORTHEASTERN CORNER
AND UPPER LEVEL MOISTURE WITH SOME BITS OF ITCZ CONVECTIVE
ACTIVITY ARE TRYING TO PUSH THEIR WAY INTO THE EXTREME
SOUTHEASTERN CORNER. BROAD UPPER LEVEL ANTICYCLONIC FLOW COVERS
THE AREA FROM 10N TO 20N BETWEEN 70W AND 80W. MIDDLE TO UPPER
LEVEL CYCLONIC FLOW STRETCHES INTO THE NORTHWESTERN CORNER OF
THE AREA FROM THE INVERTED GULF OF MEXICO TROUGH.

THE WESTERN AND CENTRAL ATLANTIC OCEAN...
T.S. FRANKLIN IS JUST NORTH OF THE AREA. CYCLONIC FLOW IS
CENTERED
NEAR 27N58W...ABOUT 700 NM EAST-SOUTHEAST OF FRANKLIN. ANOTHER
CYCLONIC CIRCULATION CENTER IS NEAR 26N75W...ABOUT 580 NM SOUTH-
SOUTHWEST OF FRANKLIN. A SURFACE TROUGH RUNS FROM 28N75W TO THE
BAHAMAS NEAR 25N76W TO 23N77W. ISOLATED MODERATE SHOWERS FROM
23N TO 26N BETWEEN 73W AND 76W. UPPER LEVEL ANTICYCLONIC FLOW
WITH A SHORTWAVE RIDGE IS JUST EAST OF THIS 26N75W CYCLONIC
CENTER. A SURFACE TROUGH CONTINUES FROM 24N65W TO THE EASTERN
DOMINICAN REPUBLIC NEAR 19N62W. ISOLATED MODERATE SHOWERS ARE
WITHIN 15 TO 30 NM ON EITHER SIDE OF 28N55W 25N58W 22N68W...AND
FROM THE EASTERN DOMINICAN TO 20N BETWEEN 67W AND 70W. THE
MID-OCEANIC TROUGH LIES FROM 30N50W TO 20N54W AND IS SHEARING
THE NORTHERN END OF THE TROPICAL WAVE APPROACHING 50W.

THE EASTERN ATLANTIC OCEAN...
A 1026 MB HIGH PRESSURE CENTER IS NEAR 31N50W...WITH THE
SUBTROPICAL RIDGE CONTINUING EAST-SOUTHEAST TO THE SOUTHERN
SECTION OF THE WESTERN SAHARA. AN UPPER HIGH IS CENTERED FARTHER
S NEAR 16N40W WITH RIDGE EXTENDING NW TO 30N44W...AND THIS IS
KEEPING THE DEEPEST ELY FLOW S OF ABOUT 16N. THE 21N48W TO 7N53W
TROPICAL WAVE IS A RATHER DEEP FEATURE...HIGHLIGHTED BY THE
INVERTED TROF NOTED IN THE UPPER LEVELS ALONG 52W. IN THE NE
ATLC...MID-LATITUDE TROUGH HAS DIPPED INTO THE AREA LONG 34N16W
TO 26N21W WITH THE ASSOCIATED COLD FRONT NOW DISSIPATED IN THE
AREA.  THE MOST NOTICEABLE EFFECT IS THE SIGNIFICANT WIND
DIRECTION CHANGE IN THE NE ATLC FROM STRONG NE TO WEAK NW NEAR
THE CANARY ISLANDS BECAUSE OF THE COMPLETE ABSENCE OF THE
SUBTROPICAL RIDGE TYPICALLY NEAR THE AZORES. WATER VAPOR
SUGGESTS THE TROPICAL ATLC IS MUCH MORE MOIST ALOFT THAN EARLIER
WITH LESS SUBSIDENCE NOTED ESPECIALLY E OF 50W. TRADE WINDS
REMAIN WEAK IN THE E ATLC WITH THE ONLY ENHANCEMENT OF TRADES
NEAR THE NORTHERN PART OF THE TROPICAL WAVE APPROACHING 50W.

$$
MT


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