[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 192349
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED AUG 19 2015

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN 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
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM DANNY CENTERED NEAR 11.5N 42.0W AT 19/2100 UTC OR
1151 NM E OF THE LESSER ANTILLES MOVING W AT 9 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND
SPEED IS 45 KT WITH GUSTS TO 55 KT. SCATTERED MODERATE AND
ISOLATED STRONG CONVECTION IS MAINLY CONFINED TO THE NW HALF OF
THE STORM WITHIN 120 NM IN THE NW SEMICIRCLE. THE OFFICIAL
FORECAST IS FOR DANNY TO STRENGTHEN TO A HURRICANE BY 48 HOURS
AS IT MOVES TO THE W-NW AT A SLIGHTLY SLOWER FORWARD SPEED. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

A TROPICAL WAVE IS MOVING ACROSS THE CAPE VERDE ISLANDS WITH
AXIS EXTENDING FROM 21N22W TO 10N24W MOVING W AT 5-10 KT. ONLY
ISOLATED SHOWERS ARE EVIDENT NEAR THE WAVE AXIS WITH THE
METEOSAT EXPERIMENTAL ENHANCED SATELLITE IMAGERY INDICATING
SAHARAN DRY AIR AND DUST SURROUNDING THE FEATURE. EVEN
SO...TOTAL PRECIPITABLE WATER SATELLITE IMAGERY INDICATES A
LARGE PLUME OF MOISTURE ASSOCIATED WITH THIS WAVE. 700 MB
STREAMLINE ANALYSIS CLEARLY SHOWS THE WAVE AXIS WHILE 850 MB
RELATIVE VORTICITY INDICATES A MAXIMUM ALONG THE WAVE AXIS.

A TROPICAL WAVE IS MOVING ACROSS THE LESSER ANTILLES EXTENDING
FROM NEAR 18N58W TO ACROSS TRINIDAD INTO NE VENEZUELA NEAR
07N62W MOVING W AT 10-15 KT. ISOLATED SHOWERS ARE POSSIBLE ALONG
THE NORTHERN HALF OF THE AXIS WHILE SCATTERED MODERATE
CONVECTION IS ASSOCIATED WITH THE PORTION S OF 12N. TPW
SATELLITE IMAGERY SHOWS A 180-240 NM WIDE POCKET OF MOISTURE
ALONG THE WAVE AXIS. 700 MB STREAMLINE ANALYSIS INDICATES
CURVATURE ALOFT ALONG THE WAVE AXIS WHILE 850 MB VORTICITY
SHOWS A MAXIMUM ACROSS NE VENEZUELA.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS ACROSS WESTERN AFRICA INTO
THE TROPICAL E ATLANTIC NEAR 13N17W TO 14N20W WHERE IT IS
DISRUPTED BY A TROPICAL WAVE THEN RESUMES FROM 13N25W TO 12N34W.
THE ITCZ AXIS EXTENDS FROM 10N46W TO 09N60W. SCATTERED MODERATE
CONVECTION IS WITHIN 90-180 NM S OF THE AXIS BETWEEN 28W-33W...
FROM 10N-13N BETWEEN 35W-39W...FROM 07N-10N BETWEEN 44W-50W...
FROM 11N-13N BETWEEN 45W-48W...AND FROM 10N-12N BETWEEN 50W-54W.

...DISCUSSION...

GULF OF MEXICO...

AN ELONGATED UPPER-LEVEL RIDGE IS OVER THE GULF EXTENDING FROM
THE FLORIDA PANHANDLE NEAR 31N85W TO THE SW THROUGH 26N90W TO SE
MEXICO OVER THE CHIVELA PASS. CONVECTION HAS DEVELOPED ACROSS
THE FLORIDA PENINSULA WITH LATE MORNING AND AFTERNOON SEABREEZE
DEVELOPMENT AND RESULTANT BOUNDARY INTERACTIONS WHILE THIS AREA
IS ALSO UNDER UPPER LEVEL DIFFLUENCE. ADDITIONAL CONVECTION HAS
DEVELOPED ACROSS THE REMAINDER OF THE U.S. GULF COAST STATES
AROUND THE UPPER RIDGE AND AHEAD OF A COLD FRONT WHICH IS
MARCHING TOWARD THE MISSISSIPPI VALLEY REGION. LIGHT TO
MODERATE ANTICYCLONIC FLOW WILL PREVAIL AT THE SURFACE ACROSS
THE NE HALF OF THE GULF THROUGH THE NEXT 48 HOURS...WITH
MODERATE TO STRONG RETURN SE FLOW ACROSS THE SW HALF OF THE
GULF...INCREASING TO FRESH TO STRONG EACH EVENING AND DURING THE
OVERNIGHT HOURS AS SURFACE TROUGHING FORMS OVER THE YUCATAN
PENINSULA BEFORE PUSHING TO THE W INTO THE SW GULF OF MEXICO.
SEAS WILL BE 1-3 FT ACROSS THE NE HALF...AND 4-6 FT ACROSS THE
SW HALF.

CARIBBEAN SEA...

A LARGE UPPER LEVEL CYCLONE LOCATED NEAR 17N82W DOMINATES THE
BASIN W OF 73W. ISOLATED SHOWERS AND TSTMS CONTINUE TO ROTATE
AROUND THE PERIPHERY OF THE LOW. AN UPPER LEVEL ANTICYCLONE IS
LOCATED OVER THE COAST OF NORTHERN VENEZUELA NEAR 10N66W WITH A
RIDGE AXIS EXTENDING OFF TO THE NW-N TO ACROSS CENTRAL
HISPANIOLA. VERY DRY AIR...STABLE CONDITIONS AND SUBSIDENCE ARE
EVIDENT E OF 73W OUTSIDE OF THE INFLUENCE OF THE APPROACHING
TROPICAL WAVE. MAINLY MODERATE TO LOCALLY FRESH TRADES WILL
PREVAIL ACROSS THE BASIN THROUGH THE NEXT 48 HOURS...EXCEPT NEAR
THE COAST OF COLOMBIA AND IN THE GULF OF VENEZUELA WHERE STRONG
TO NEAR GALE FORCE WINDS WILL PERSIST...AND IN THE GULF OF
HONDURAS WHERE WINDS WILL PULSE TO FRESH TO STRONG DURING THE
OVERNIGHT HOURS. SEAS WILL BE MAINLY 3-6 FT...EXCEPT UP TO 13 FT
NEAR THE COAST OF COLOMBIA AND UP TO 7 FT IN THE GULF OF
HONDURAS.

...HISPANIOLA...

MAINLY FAIR WEATHER PREVAILS ACROSS THE ISLAND...EXCEPT FOR A
FEW WIDELY ISOLATED SHOWERS AND TSTMS WHICH HAVE DEVELOPED
WITH THE ASSISTANCE OF DAYTIME HEATING AND OROGRAPHIC LIFTING.
SIMILAR CONDITIONS ARE ANTICIPATED FOR THU HOWEVER PRECIPITATION
CHANCES ARE FORECAST TO INCREASE THU NIGHT THROUGH FRI AS A
TROPICAL WAVE APPROACHES FROM THE E.

ATLANTIC OCEAN...

AN UPPER LEVEL RIDGE IS ACROSS THE SE PART OF THE SW N ATLC
OFFSHORE WATERS EXTENDING FROM THE NORTHERN BAHAMAS TO THE
SE-E NEAR 24N65W...WHILE BROAD MID TO UPPER LEVEL TROUGHING IS
MOVING ACROSS THE NORTHERN PORTION. SCATTERED SHOWERS AND
TSTMS ASSOCIATED WITH THE TROUGHING ARE PASSING THROUGH THE
WATERS N OF 27N...WHILE THE AREA S OF 27N REMAINS MAINLY CLEAR.
1020 MB SURFACE HIGH PRES IS LOCATED NEAR 27N67W WITH A RIDGE
AXIS EXTENDING WESTWARD ALONG 27N. LIGHT TO MODERATE
ANTICYCLONIC WINDS PREVAIL AT THE SURFACE...EXCEPT AROUND THE SW
PERIPHERY OF THE RIDGE WHERE SCATTEROMETER DATA INDICATED
MODERATE TO LOCALLY FRESH WINDS. LITTLE CHANGE IN THESE
CONDITIONS IS EXPECTED DURING THE NEXT 48 HOURS WITH MAINLY 2-4
FT SEAS...EXCEPT 4-6 FT S OF 22N. AN EXCEPTION WILL BE THE
INTRODUCTION OF A SURFACE LOW WHICH WILL DROP IN FROM E OF THE
CAROLINAS INTO THE NE PORTION OF THE SW N ATLC BY EARLY THU
DRAGGING A TRAILING SURFACE TROUGH ACROSS THE AREA. WINDS MAY
INCREASE TO 20-25 KT AHEAD OF THE TROUGH BY THU AFTERNOON TROUGH
FRI. ANOTHER HIGH AT 1022 MB IS LOCATED NEAR 28N50W WITH MAINLY
LIGHT TO MODERATE WINDS N OF 20N ACROSS THE REMAINDER OF THE
BASIN.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
LEWITSKY
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