[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 041804
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN SEP 04 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 FEATURE...

THE CENTER OF HURRICANE MARIA AT 04/1500 UTC WAS NEAR
28.8N 55.5W OR ABOUT 605 MILES/970 KM EAST-SOUTHEAST OF BERMUDA.
IT WAS MOVING NORTH-NORTHWEST 11 KT. THE ESTIMATED MINIMUM
CENTRAL PRESSURE WAS 987 MB. THE MAXIMUM SUSTAINED WIND SPEEDS
WERE 65 KT WITH GUSTS TO 80 KT. PLEASE REFER TO THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
AND THE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/
WTNT34 KNHC FOR MORE DETAILS.  MARIA HAS FAIRLY WELL-ESTABLISHED
UPPER-LEVEL OUTFLOW...PARTICULARLY IN CHANNELS TO THE NORTHWEST
AND SOUTHEAST. IT IS LIKELY THAT MARIA WILL CONTINUE TO CROSS
WARM ATLANTIC OCEAN WATERS. THIS MEANS THAT STRENGTHENING
IS LIKELY UNTIL WESTERLY VERTICAL SHEAR INCREASES SIGNIFICANTLY.
THIS INCREASE IS EXPECTED TO OCCUR IN 48 HOURS OR SO. THE
GUIDANCE FROM GLOBAL MODELS SUGGESTS THAT MARIA WILL BE
TRANSFORMING INTO A VIGOROUS EXTRATROPICAL CYCLONE IN FOUR
TO FIVE DAYS. NUMEROUS STRONG SHOWERS AND THUNDERSTORMS FROM
28N TO 30N BETWEEN 54W AND 57W. ISOLATED MODERATE SHOWERS AND
THUNDERSTORMS ELSEWHERE FROM 26N TO 31N BETWEEN 52W AND 58W.

...TROPICAL WAVES...

EASTERN ATLANTIC OCEAN TROPICAL WAVE ALONG 18W/19W SOUTH OF 25N
MOVING WEST 10 KT. A 1011 MB LOW PRESSURE CENTER IS ALONG THIS
WAVE NEAR 14N. A BROAD CYCLONIC CIRCULATION IS DETECTED IN THE
LATEST VISIBLE SATELLITE IMAGERY FROM 11N TO 12N ALONG 22W/23W.
ISOLATED MODERATE SHOWERS AND LOCALLY STRONG THUNDERSTORMS...
WITH SOME AREAS OF WARMING CLOUD TOP TEMPERATURES...FROM 10N TO
16N BETWEEN 18W AND 22W. SIMILAR PRECIPITATION AND CLOUDS ARE
FOUND FROM 4N TO 10N BETWEEN 16W AND 31W...PROBABLY MORE RELATED
TO THE ITCZ THAN TO THIS WAVE.

EAST CENTRAL ATLANTIC OCEAN TROPICAL WAVE IS ALONG 31W/32W
SOUTH OF 18N MOVING WEST 10 KT. ISOLATED MODERATE SHOWERS
FROM 5N TO 14N BETWEEN 30W AND 35W. THIS WAVE IS THE WEAKEST OF
THE THREE WHICH ARE EAST OF THE LESSER ANTILLES. IT IS FORECAST
BY THE GFS MODEL TO MOVE WESTWARD WITHOUT MUCH PRECIPITATION
DURING THE NEXT SEVERAL DAYS...POSSIBLY ENTERING THE LESSER
ANTILLES LATE IN THE WEEK.

ATLANTIC OCEAN TROPICAL WAVE IS ALONG 48W SOUTH OF 18N MOVING
WEST 10-15 KT. A 1014 MB LOW IS ALONG THE WAVE NEAR 11N.
WIDELY SCATTERED TO SCATTERED MODERATE SHOWERS/ISOLATED STRONG
THUNDERSTORMS FROM 8N TO 11N BETWEEN 49W AND 55W...BECOMING
ISOLATED MODERATE TO LOCALLY STRONG FROM 12N TO 15N BETWEEN 49W
AND 52W. SIGNIFICANT DEVELOPMENT OF THIS SYSTEM INTO A TROPICAL
CYCLONE IS NOT EXPECTED OVER THE NEXT COUPLE OF DAYS. THE
WESTERN FRINGE OF INCREASED MOISTURE SHOULD REACH THE LESSER
ANTILLES ON MONDAY PROBABLY INCREASING THE CHANCE OF RAIN
THROUGH TUESDAY.

A CENTRAL CARIBBEAN SEA TROPICAL WAVE IS ALONG 78W/79W SOUTH
OF 17N AND JAMAICA MOVING WEST 15 KT. THIS POSITION IS BASED
ON EXTRAPOLATION. A MIDDLE TO UPPER LEVEL TROUGH REACHES THE
NORTHWESTERN CORNER OF THE CARIBBEAN SEA. UPPER LEVEL
ANTICYCLONIC FLOW GOES THROUGH THIS TROUGH AND SHOOTS OUT
EASTWARD AND CURVES ANTICYCLONICALLY SOUTHEASTWARD OVER THE
TOP OF THIS WAVE. SHOWERS AND THUNDERSTORMS IN ONE CLUSTER
WITHIN 15 NM RADIUS OF 12N78.5W.

...THE ITCZ...

ITCZ 10N20W 11N30W...12N34W 12N46W...9N50W 6N60W. ISOLATED
MODERATE SHOWERS AND LOCALLY STRONG THUNDERSTORMS...WITH SOME
AREAS OF WARMING CLOUD TOP TEMPERATURES...FROM 4N TO 10N BETWEEN
16W AND 31W. WIDELY SCATTERED TO SCATTERED MODERATE SHOWERS/
ISOLATED STRONG THUNDERSTORMS FROM 8N TO 11N BETWEEN 49W AND
55W...MAY BE RELATED TO THE INTERACTION BETWEEN THE WAVE AND
THE ITCZ.

...DISCUSSION...

THE GULF OF MEXICO...
MIDDLE TO UPPER LEVEL IS ON A LINE FROM THE BAHAMAS ACROSS
SOUTH FLORIDA INTO THE SOUTHEASTERN GULF WATERS. UPPER LEVEL
SOUTHWESTERLY WINDS START TO CUT INTO THE PURE ANTICYCLONIC
FLOW OF THIS RIDGE...FROM THE CENTRAL GULF TOWARD THE
SOUTHEASTERN SECTION. THIS IS HAPPENING IN ADVANCE OF A MIDDLE
TO UPPER LEVEL TROUGH...WHICH IS MOVING FROM TEXAS SOUTHEASTWARD
INTO THE NORTHWESTERN AND NORTH CENTRAL GULF. AN UPPER LEVEL
TROUGH CONTINUES FROM THE NORTHWESTERN CARIBBEAN SEA ACROSS THE
YUCATAN PENINSULA INTO THE SOUTHWESTERN CORNER OF THE GULF.
WIDELY SCATTERED TO SCATTERED MODERATE SHOWERS/ISOLATED STRONG
THUNDERSTORMS ARE SOUTH OF 24N WEST OF 90W. SLIGHTLY MORE
SCATTERED PRECIPITATION IS MAKING ITS WAY WESTWARD FROM THE
BAHAMAS TOWARD CUBA AND FLORIDA...FROM CUBA TO 28N BETWEEN
76W AND 83W IN THE EASTERN GULF WATERS/SHORES.

THE CARIBBEAN SEA...
UPPER TROUGH IS LOCATED OVER THE NW CARIBBEAN EXTENDING FROM
WESTERN HAITI INTO A LOW NEAR 19N86W THEN WEST-SOUTHWEST INTO
BELIZE. THE WEATHER IS RATHER QUIET OVER THE OPEN WATERS WITH
DRY AIR ALOFT EAST OF 75W. WIDELY SCATTERED TO SCATTERED
MODERATE SHOWERS/ISOLATED STRONG THUNDERSTORMS FROM 15N TO 17N
BETWEEN 81W AND 86W...AND OTHER ISOLATED MODERATE SHOWERS FROM
12N TO 15N BETWEEN 80W AND CENTRAL AMERICA...IN AN AREA OF
SOME UPPER LEVEL DIFFLUENT FLOW. UPPER LEVEL ANTICYCLONIC FLOW
COVERS THE REST OF THE WESTERN AND SOUTHWESTERN SECTIONS.
THE WINDWARD ISLANDS LOOK QUITE DRY TODAY BEFORE INCREASING
TROPICAL MOISTURE COMES ON MONDAY...WITH SEASONABLE CONDITIONS
IN THE LEEWARD ISLANDS FOR THE NEXT COUPLE OF DAYS...THOUGH
WINDS LOOK FAIRLY LIGHT.

THE WESTERN ATLANTIC OCEAN...
A SURFACE TROUGH CONNECTS A 1011 MB SURFACE LOW PRESSURE CENTER
NEAR 32N66W TO A 1010 MB LOW CENTER NEAR 29N67W...CONTINUING TO
24N70W AND THE BAHAMAS NEAR 24N78W. SCATTERED MODERATE SHOWERS
TO ISOLATED STRONG THUNDERSTORMS FROM CUBA TO 28N BETWEEN 76W
AND 83W IN THE EASTERN GULF WATERS/SHORES...AND IN THE ATLANTIC
WATERS FROM 22N TO 27N BETWEEN 63W AND 70W. ISOLATED MODERATE
SHOWERS AND LOCALLY STRONG THUNDERSTORMS FROM 28N TO 32N BETWEEN
67W AND 69W. AN UPPER TROUGH REMAINS GOES FROM 31N64W TO 25N70W
ASSISTING TSTM DEVELOPMENT.  THIS TROUGH HAS BEEN WEAKENING WITH
TIME AND COUPLED WITH THE BUILDING UPPER HIGH OVER THE W ATLC
NEAR 28N75W... COULD ALLOW SLOW TROPICAL CYCLONE DEVELOPMENT.
COMPUTER MODELS ALSO SUGGEST THIS POSSIBILITY THOUGH THEY DO NOT
AGREE ON EXACTLY WHERE IT WILL OCCUR ALONG THE SURFACE TROUGH.

THE EASTERN AND CENTRAL ATLANTIC OCEAN...
ALMOST ALL OF THE TSTMS IN THE SUBTROPICAL ATLC E OF 60W ARE
CONCENTRATED AROUND MARIA WHICH SITS BENEATH AN UPPER HIGH
HELPING TO EXPAND ITS OUTFLOW GREATLY TO THE N.  FARTHER E...
DEEP LOW IS NEAR THE AZORES WITH A DISSIPATED COLD FRONT STILL
PRODUCING OVERCAST LOW CLOUDS N OF 26N BETWEEN 25W-31W.
ASSOCIATED UPPER TROUGH IS STRONG FOR EARLY SEPT WITH A COLD LOW
FORMING NEAR 31N34W TROUGHING S TO 22N36W.  THE ATLC UPPER RIDGE
IS SPLIT INTO TWO BY THIS TROUGH IN COMBINATION WITH AN INVERTED
TROUGH FROM 9N39W TO 20N35W WITH ONE HIGH NEAR 19N53W AND THE
OTHER OVER W AFRICA. SURFACE WINDS HAVE INCREASED TO NEAR
AVERAGE LEVELS EAST OF 50W AS THE ATLC RIDGE BUILDS IN A BIT
OVER THE EASTERN ATLANTIC OCEAN. BELOW AVERAGE PRESSURES IN THE
DEEP TROPICS RECENTLY HAVE REVERSED INTO BEING SLIGHTLY ABOVE
AVERAGE...PERHAPS INDICATIVE THAT THE ACTIVE CONVECTION PHASE OF
THE MADDEN-JULIAN OSCILLATION HAS LEFT THE REGION.

$$
MT





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