[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 291806
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT JUN 29 2013

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE EXTENDS ROUGHLY ALONG 29W FROM 17N TO 09N MOVING
W AT 5-10 KT. ONLY SUBTLE MID-LEVEL CYCLONIC CIRCULATION IS
EVIDENT NEAR 13N. OTHERWISE...THE WAVE REMAINS ILL-DEFINED AT
THE SURFACE...BUT SHOWS UP NICELY IN THE LATEST GFS 700 MB MODEL
STREAMLINE ANALYSIS...AND IS HINTED AT ON POTENTIAL VORTICITY
ANALYSIS.

A WELL-DEFINED TROPICAL WAVE FOR THIS EARLY IN THE SEASON HAS
ENTERED THE EASTERN CARIBBEAN SEA...AND IS VIVIDLY OBSERVED
ALONG A POSITION FROM JUST W OF GAUDELOUPE TO WEAKENING LOW PRES
OF 1012 MB AT 12N64W...AND TO INLAND VENEZUELA TO 09N65W. THE
WAVE WAS PLACED AT THIS POSITION BASED ON ISLAND SURFACE
OBSERVATIONS AS WELL NEARBY BUOY REPORTS. IT IS MOVING IN A
GENERAL WESTWARD DIRECTION AT ABOUT 15-20 KT. THE WAVE CONTINUES
TO COINCIDES WITH A LARGE SURGE OF DEEP LAYER MOISTURE PRESENT
IN TOTAL PRECIPITABLE COMPOSITE WATER IMAGERY...WITH THE
EXCEPTION OF THE NRN PORTION WHICH APPEARS TO BE DIMINISHING IN
MOISTURE CONTENT. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS NOTED FROM 09N-15N BETWEEN 55W-62W. SIMILAR ACTIVITY IS
SHEARING OFF TO THE NE FROM 15N-20N BETWEEN 54W-58W. THE 1012 MB
LOW ALONG THE WAVE IS FORECAST TO DISSIPATE OVER THE NEXT 24
HOURS.

A TROPICAL WAVE IS MOVING THROUGH THE WESTERN CARIBBEAN ALONG
81W FROM 10N TO 20N. IT IS MOVING W AT AN ESTIMATED SPEED OF 16
KT. THE TOTAL PRECIPITABLE COMPOSITE WATER IMAGERY SHOWS A
RATHER BROAD SURGE OF DEEP LAYER MOISTURE ALONG AND TO WITHIN
300 NM E OF THE WAVE AXIS...WITH LESSER PRONOUNCED DEEP LAYER
MOISTURE TO ITS E. THE WAVE IS ENHANCING SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION OVER S CENTRAL CUBA. SCATTERED
MODERATE TO STRONG CONVECTION IN CLUSTERS ARE WITHIN 180 NM E OF
THE WAVE AXIS FROM 15N TO 19N.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE COAST OF GUINEA-BISSAU NEAR
12N16W TO 9N20W TO 7N26W. THE ITCZ BEGINS NEAR 07N26W...AND
CONTINUES TO 06N30W TO 3N38W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 60 NM OF THE MONSOON TROUGH AXIS BETWEEN
19W-26W. SIMILAR CONVECTION IS S OF THE MONSOON TROUGH WITHIN 60
NM OF LINE 9N14W TO 09N19W. SCATTERED MODERATE CONVECTION IS
WITHIN 60 NM OF THE ITCZ AXIS BETWEEN 26W-28W.

...DISCUSSION...

GULF OF MEXICO...
THE WESTERN EXTENSION OF ATLANTIC SURFACE RIDGING HAS SHIFTED S
OVER THE PAST 12-24 HRS...AND IS CURRENTLY ANALYZED FROM THE
STRAITS OF FLORIDA TO EASTERN BAY OF CAMPECHE. TO THE N OF THIS
RIDGE...LIGHT SW-W WINDS ARE BEING REPORTED BY BUOYS AND
PLATFORMS ACROSS THE AREA. IN THE UPPER LEVELS...A LONGWAVE
TROUGH APPROACHING THE EASTERN U.S EXTENDS SSW TO THE FAR
N/CENTRAL GULF. A SHORTWAVE TROUGH ROUNDING THE BASE OF THIS
LONGWAVE TROUGH IS MOVING SEWD ACROSS THE N FLORIDA AND SE
GEORGIA. TO THE SW OF THE LONGWAVE TROUGH...A MID/UPPER TROUGH
EXTENDS FROM NEAR 28N90W SW TO A SMALL UPPER LOW AT 24N94W. A
SOMEWHAT DIFFLUENT FLOW BETWEEN THE UPPER LOW AND TROUGHS TO THE
N IS ALLOWING FOR SCATTERED MODERATE TO AT TIMES STRONG
THUNDERSTORMS WITH GUSTY WINDS CONFINED TO THE NORTHERN PORTION
N OF 27N AND E OF 93W. ONLY ISOLATED SHOWERS AND WEAK
THUNDERSTORMS ARE NOTED S OF 27N E OF 93W. WITH LITTLE EWD
PROGRESSION EXPECTED WITH THE AFOREMENTIONED LONGWAVE TROUGH AS
SHORTWAVE ENERGY CONTINUES TO ROUND ITS BASE OVER THE 24-48
HOURS...EXPECT THE UNSETTLED WEATHER IN THE NORTHERN GULF TO
LAST THROUGH THE NEXT COUPLE OF DAYS. THE SURFACE RIDGE WILL
SINK A LITTLE TO THE S THROUGH SUN...THEN REFORM OVER THE
EASTERN GULF MON.

CARIBBEAN SEA...
THE TROPICAL WAVE POSITIONED ALONG 81W IS ONE OF THE MAIN
WEATHER PRODUCERS FEATURES IMPACTING THE CARIBBEAN. IN ADDITION
TO ITS ASSOCIATED CONVECTION AS DESCRIBED ABOVE...SCATTERED
SHOWERS AND ISOLATED TSTMS ARE RAPIDLY DEVELOPING TO ITS W OVER
THE FAR WESTERN CARIBBEAN S OF 16N...AND ARE BEING FURTHER
FUELED BY THE EASTERN SEGMENT OF THE PACIFIC MONSOON TROUGH THAT
EXTENDS FROM SOUTHERN NICARAGUA SW TO NORTHERN COLOMBIA. THE
WAVE WILL MOVE THROUGH MOST OF THE WESTERN CARIBBEAN AND ACROSS
HONDURAS AND NICARAGUA THROUGH THE NEXT 48 HRS. ISOLATED SHOWERS
AND WEAK THUNDERSTORMS ARE OVER PORTIONS OF THE NW CARIBBEAN.
ISOLATED SHOWERS AND WEAK THUNDERSTORMS ARE ALSO OVER MUCH OF
CENTRAL AMERICA EARLY THIS AFTERNOON. EXPECT THIS ACTIVITY TO
POSSIBLY INCREASE DURING THE COURSE OF THE AFTERNOON AND EVENING
AS RIDGING IN THE UPPER LEVELS PREVAILS FROM CENTRAL AMERICA E
TO CENTRAL CARIBBEAN.

TO THE E OF THE WAVE...SATELLITE IMAGERY AND STATION
OBSERVATIONS INDICATE MOSTLY FAIR TO PARTLY CLOUDY SKIES WITH
SOME TRACES OF HAZE OVER THE NE PART OF THE CARIBBEAN. THE
OBSERVATIONS SHOW GENERAL TRADES WITH SPEEDS OF 10-15 KT...
EXCEPT 15-20 KT E OF THE WAVE AND LIGHTER WINDS...SE-S AT 5 KT
IN THE NW CARIBBEAN SECTION.

SATELLITE WATER VAPOR IMAGERY SHOWS AN UPPER TROUGH OVER THE
EASTERN CARIBBEAN THAT EXTENDS FROM AN UPPER LOW OVER THE
ATLANTIC AT 22N565W SW TO THE VICINITY OF PUERTO RICO AND TO
NEAR 11N68W. THIS FEATURE IS ADVERSELY IMPACTING THE EASTERN
CARIBBEAN TROPICAL WAVE DESCRIBED ABOVE BY SHEARING IT. VISIBLE
SATELLITE IMAGERY SHOWS CURVED LINES OF LOW CLOUDS WITH ISOLATED
SHOWERS RACING WESTWARD OUT AHEAD OF THE WEAK 1012 MB LOW ON THE
WAVE. THESE CLOUDS REACH TO NEAR 67W. THE WAVE IS FORECAST TO
REACH THE CENTRAL CARIBBEAN BY EARLY MON.

HISPANIOLA...
ISOLATED SHOWERS AND THUNDERSTORMS ARE DEVELOPING OVER THE
INTERIOR PORTIONS OF HISPANIOLA. IT APPEARS THIS ACTIVITY WILL
LIKELY CONTINUE TO INCREASE THROUGH THE REST OF THE DAY. MID TO
UPPER LEVEL NW FLOW IS ACROSS THE ISLAND AS UPPER RIDGING IS
SITUATED ACROSS THE WESTERN CARIBBEAN. SHOWERS AND THUNDERSTORMS
ARE AGAIN EXPECTED TO FORM OVER THE INTERIOR OF HISPANIOLA ON
SUN...THEN DEPENDING ON HOW MUCH MOISTURE REMAINS FROM THE
EASTERN CARIBBEAN WAVE ONCE IT PASSES S OF THE ISLAND IN ABOUT
48 HRS...THE SHOWER/THUNDERSTORM MAY INCREASE IN COVERAGE OR
STAY ABOUT THE SAME AS IT IS EXPECTED FOR THE REST OF TODAY AND
ON SUN.

ATLANTIC OCEAN...
BROAD SURFACE RIDGING COVERS THE WEST ATLC AROUND A 1031 MB HIGH
CENTERED N OF THE AREA AT 42N30W. IN THE UPPER LEVELS...A LOW IS
NOTED AT 22N65W...AND ANOTHER MUCH SMALLER ONE NEAR THE NORTHERN
BAHAMAS. ACTIVE THUNDERSTORM ACTIVITY OF MODERATE INTENSITY IS S
OF THE THIS LOW OVER MUCH OF THE CENTRAL AND SE BAHAMAS. AN
UPPER TROUGH EXTENDS FROM THE LOW AT 22N65W SW TO THE NE
CARIBBEAN SEA. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS HAVE
MOVED INTO THE FAR NW PORTION OF THE BASIN AHEAD OF THE E COAST
UPPER TROUGH.

THE REMAINDER OF THE BASIN IS CONTINUES UNDER THE DOMINANCE OF
BROAD SURFACE RIDGING ASSOCIATED WITH 1031 MB HIGH...AND THIS
PATTERN CONTROLS THE GENERAL WIND REGIME THROUGHOUT.
ALOFT...UPPER RIDGING COVERS MOST OF THE AREA WITH AN AXIS
EXTENDING FROM THE TROPICAL ATLANTIC NEAR 12N48W TO NEAR 30N22W.
AN UPPER LOW IS TO THE NE OF THE AREA NEAR 31N41W. ISOLATED
THUNDERSTORMS ARE WITHIN 120 NM OF THE LOW IN THE SE AND S
QUADRANTS. VISIBLE SATELLITE IMAGERY AND SATELLITE DUST DATA
SHOWS A LARGE AREA OF SAHARAN DUST EXTENDING FROM THE COAST OF
AFRICA TO NEAR 49W AROUND THE TROPICAL WAVE IN THE EASTERN
ATLANTIC.

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

$$
AGUIRRE


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