[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 111146
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT JUNE 11 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...SPECIAL FEATURE...
TROPICAL STORM ARLENE IS CENTERED NEAR 29.0N 87.2W AT 11/1200
UTC...OR ABOUT 115 MILES EAST OF THE MOUTH OF THE MISSISSIPPI
RIVER...MOVING NNW AT 13 KT. MAXIMUM SUSTAINED WIND SPEED 60 KT
GUSTING TO 75 KT. MINIMUM CENTRAL PRESSURE 990 MB. SEE LATEST
NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21
KNHC AND/OR MIATCPAT1/WTNT31 FOR MORE DETAILS. BURST OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS JUST NW OF THE
CENTER OF ARLENE WHILE THE REMAINDER OF THE DEEP CONVECTION HAS
SLOWLY DISSIPATED OVER THE LAST 6 HOURS. HEAVY RAIN AND
THUNDERSTORMS  REMAIN N AND E OF THE CENTER THIS MORNING. ARLENE
REMAINS ALONG THE NW PERIPHERY OF AN UPPER RIDGE AXIS EXTENDING
FROM OVER THE NW CARIBBEAN. THIS POSITION IS FAVORABLE FOR
INTENSIFICATION WITH MORE OF A S FLOW AFFECTING THE TROPICAL
CYCLONE. DRY AIR ALOFT IS BEING ENTRAINED INTO ARLENE BUT DOES
NOT APPEAR TO BE IMPEDING FURTHER DEVELOPMENT. THE CYCLONE IS
VERY CLOSE TO HURRICANE STRENGTH AND FURTHER INTENSIFICATION
COULD BE EXPECTED BEFORE ARLENE MAKES LANDFALL LATER TODAY.
HEAVY RAINS/ THUNDERSTORMS THAT HAVE BEEN AFFECTING FLORIDA HAVE
DECREASED S OF LAKE OKEECHOBEE AND THIS TREND WILL CONTINUE
THROUGH THE DAY FROM SOUTH TO NORTH.

...TROPICAL WAVES...

CENTRAL ATLC TROPICAL WAVE IS ALONG 38W S OF 16N MOVING W 10 KT.
WAVE REMAINS ALONG THE LEADING EDGE OF AFRICAN DUST WITH A
SLIGHT CURVATURE NOTED ON INFRARED SATELLITE IMAGERY. NO
ASSOCIATED DEEP CONVECTION.

W ATLC TROPICAL WAVE IS ALONG 57W/58W S OF 16N MOVING W 10 KT.
WAVE IS BENEATH A COL BETWEEN UPPER RIDGES ACROSS THE TROPICAL
ATLC. THIS SCENARIO IS ENHANCING CONVECTION ASSOCIATED WITH THIS
WAVE. LARGE AREA OF SCATTERED MODERATE/STRONG CONVECTION IS FROM
10N-21N BETWEEN 48W-57W.

CARIBBEAN TROPICAL WAVE IS ALONG 79W S OF 18N MOVING W 10 KT.
STRONG N UPPER FLOW OVER THE AREA IS MASKING THE EXACT POSITION
BUT THERE IS SOME HINT IN THE LOW CLOUDS THAT COULD BE THE
WAVE'S LOCATION. WAVE COUPLED WITH A WEAK 1008 MB LOW OVER
COLOMBIA ARE ENHANCING SCATTERED/NUMEROUS STRONG CONVECTION
COVERING THE AREA S OF 11N BETWEEN 74W-78W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 13N14W 8N24W 6N36W 11N63W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 90/120 NM OF THE
AXIS FROM 45W-57W...WITHIN 75 NM OF LINE COAST OF AFRICA NEAR
10N14W-7N18W...AND WITHIN 60 NM OF LINE FROM 5N28W-3N34W.
SCATTERED CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM
5N-10N BETWEEN 21W-46W.

...DISCUSSION...

GULF OF MEXICO...
ARLENE DOMINATES THE WEATHER PICTURE IN THE GULF WITH OVERCAST
MULTILAYERED CLOUDS WITH SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS COVERING THE REMAINDER OF THE AREA N OF 27N E OF
89W AND N OF 26N E OF 83W. BROAD MID/UPPER TROUGH EXTENDS FROM
THE CENTRAL UNITED STATES S ALONG THE TEXAS/MEXICAN COAST TO THE
W BAY OF CAMPECHE WITH ARLENE EMBEDDED WITHIN THIS FLOW. THIS IS
PRODUCING SW UPPER FLOW ACROSS THE ENTIRE GULF. THE WET PATTERN
COULD CONTINUE FOR THE WEEKEND OVER FLORIDA AS THE UPPER LEVEL
RIDGE REMAINS OFF THE E COAST OF FLORIDA AND THE HEATING OF THE
DAY COULD GENERATE SHOWERS AND THUNDERSTORMS EVEN THOUGH ARLENE
WILL BE MOVING INLAND. REMAINDER OF THE GULF IS UNDER STRONG
SUBSIDENCE AND DRY AIR...RESULTING IN CLEAR SKIES THAT WILL
GRADUALLY SPREAD TO W COAST OF FLORIDA WITH THE PASSAGE OF
ARLENE LATER TODAY.

CARIBBEAN SEA...
UNSETTLED WEATHER PATTERN CONTINUES OVER THE CARIBBEAN WITH A
MID/UPPER LEVEL HIGH OVER THE W CARIBBEAN JUST W OF JAMAICA NEAR
18N79W AND A RIDGE AXIS EXTENDING NE ACROSS CUBA THEN N INTO THE
W ATLC. A MID/UPPER TROUGH FROM THE CENTRAL ATLC CONTINUES TO
CLIP THE NE CARIBBEAN FROM HISPANIOLA TO THE LEEWARD ISLANDS.
UPPER LEVEL S TO SW FLOW COVERS THE REMAINDER OF THE AREA.
DIFFLUENCE OVER THE GREATER ANTILLES CONTINUES TO GENERATE
SCATTERED MODERATE/ISOLATED STRONG TO SCATTERED STRONG
CONVECTION FROM 14N-20N BETWEEN 58W-70W. A LOWER EXTENT OF A
RAINBAND FROM ARLENE AND TROPICAL WAVE ALONG 79W ARE GENERATING
SCATTERED STRONG CONVECTION N OF 16N TO OVER CUBA FROM 77W-80W.
A WET WEEKEND IS LIKELY FOR THE N PORTION OF THE CARIBBEAN WITH
PLENTY OF UPPER SUPPORT AND DEEP-LEVEL MOISTURE FOR HEAVY
RAIN...ALONG WITH A TROPICAL WAVE MOVING IN FROM THE W TROPICAL
ATLC TO PROVIDE ANOTHER FOCUS FOR RAIN.

ATLANTIC OCEAN...
MID/UPPER LEVEL RIDGE IN THE FAR W ATLC EXTENDS FROM AN UPPER
HIGH IN THE W CARIBBEAN ACROSS CENTRAL CUBA THEN NE ALONG THE E
COAST OF FLORIDA TO INLAND OVER SOUTH CAROLINA. THIS RIDGE IS
FORECASTED TO REMAIN NEARLY STATIONARY FOR THE DAY OR TWO AND
WITH THE LANDFALL OF ARLENE WILL BRING ANOTHER WET WEEKEND TO
FLORIDA AND THE FAR SE UNITED STATES. OVERCAST MULTILAYERED
CLOUDS WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS COVER THE W
ATLC INCLUDING THE N BAHAMAS W OF 75W RESULTS OF THE OUTFLOW
FROM ARLENE. OVER THE CENTRAL ATLC...A MID/UPPER LEVEL LOW
REMAINS CENTERED NEAR 25N62W DRIFTING SW WITH AN UPPER TROUGH
DIPPING AS FAR S AS 16N FROM 55W-70W INCLUDING THE NE CARIBBEAN
ISLANDS FROM HISPANIOLA TO THE LEEWARD ISLANDS. A BUILDING
MID/UPPER LEVEL RIDGE TO THE E OF THIS SYSTEM AND A SURFACE
TROUGH THAT EXTENDS FROM 27N62W THROUGH THE MONA PASSAGE TO
16N70W IN THE N CARIBBEAN ARE RESPONSIBLE FOR A LARGE AREA OF
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 30N FROM 55W-67W
WITH HEAVIEST AREA OF ACTIVITY ENHANCED BY THE TROPICAL WAVE
ALONG 57W/58W. THE UPPER LOW AND SURFACE TROUGH ARE FORECASTED
TO RETROGRADE SLOWLY W OVER THE NEXT COUPLE OF DAYS CONTINUING
THE SHOWER ACTIVITY FOR THE WEEKEND. BROAD UPPER TROUGH COVERS
THE REMAINDER OF THE ATLC E OF 45W...THUS RESULTING IN LITTLE
INTEREST WEATHER-WISE. AT THE SURFACE...BROAD BUT WEAK HIGH
PRESSURE DOMINATES THE ATLC N OF 20N FROM 20W-50W AND N OF 25N W
OF 50W TO THE E COAST OF THE UNITED STATES. FARTHER S IN THE
TROPICAL ATLC...MID/UPPER RIDGE EXTENDS ALONG 11N/12N E OF 50W
THUS SUPPRESSING THE ITCZ AXIS TO THE S. AREA OF AFRICAN DUST
CAN BE SEEN ON THE FIRST VISIBLE SATELLITE IMAGES E OF 34W.

$$
WALLACE



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