[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT OCT 20 2012

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
1715 UTC.

...SPECIAL FEATURES...

TROPICAL WAVE EXTENDS FROM 12N71W TO 19N73W MOVING W AT 5-10 KT.
LOW-LEVEL CYCLONIC FLOW IS EVIDENT ON VISIBLE SATELLITE IMAGERY
WITH TOTAL PRECIPITABLE WATER IMAGERY ALSO INDICATING MAXIMUM
VALUES OF DEEP LAYER MOISTURE ACROSS THE CENTRAL CARIBBEAN
BETWEEN 69W-77W. UNORGANIZED SCATTERED MODERATE CONVECTION
ACCOMPANIES THE WAVE OVER A LARGE AREA FROM 11N-19N BETWEEN
64W-76W. WITH AN UPPER LEVEL ANTICYCLONIC CENTERED OVER THIS
TROPICAL WAVE...ENVIRONMENTAL CONDITIONS ARE FORECAST TO BECOME
MORE FAVORABLE FOR DEVELOPMENT DURING THE NEXT DAY OR TWO AS THE
DISTURBANCE MOVES WESTWARD. THIS SYSTEM HAS A HIGH CHANCE OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 15N45W TO 23N47W MOVING W AT 10-15
KT. A 1012 MB LOW IS CENTERED ALONG THE WAVE AXIS NEAR 17N46W AS
NOTED ON METEOSAT-9 VISIBLE SATELLITE IMAGERY...HOWEVER A
20/1228 UTC ASCAT PASS SHOWED A STRONG WIND FIELD...NE TO E
WINDS IN THE RANGE OF 20 TO 25 KT...FROM 21N-23N BETWEEN
44W-47W. THIS AREA CLOSELY MIRRORS AN AREA OF SCATTERED MODERATE
CONVECTION FROM 20N-24N BETWEEN 42W-48W AND IS LIKELY ENHANCED
BY UPPER LEVEL DIFFLUENCE DUE TO AN UPPER LEVEL LOW CENTERED
NEAR 19N51W.

TROPICAL WAVE EXTENDS FROM 13N56W TO 21N57W MOVING W AT 10-15
KT. THE WAVE REMAINS DIFFICULT TO DISCERN ON SATELLITE
IMAGERY...HOWEVER DOES COINCIDE WITH VERY WEAK LOW-LEVEL
CYCLONIC STREAMLINES ON RECENT GLOBAL MODEL DATA ALONG 57W. NO
SIGNIFICANT CONVECTION IS NOTED WITH THE WAVE AT THIS TIME.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N17W TO
09N21W TO 11N30W TO 07N38W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 07N38W TO 05N42W TO 01N50W. SCATTERED MODERATE
AND ISOLATED STRONG CONVECTION IS FROM 04N-13N BETWEEN 16W-25W.
WIDELY SCATTERED MODERATE CONVECTION IS FROM 09N-13N BETWEEN
25W-30W...AND FROM 06N-12N BETWEEN 30W-36W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYERED LOW IS CENTERED OVER THE GREAT LAKES REGION AND
PROVIDES MIDDLE TO UPPER LEVEL TROUGHING OVER MUCH OF THE
EASTERN CONUS. THIS TROUGHING DIPS SOUTHWARD INFLUENCING THE
GULF BASIN WITH MOSTLY DRY AND STABLE NW WINDS ALOFT. THE TROUGH
HOWEVER DOES SUPPORT A VERY SHALLOW COLD FRONT ANALYZED FROM
27N81W TO 24N89W. WHILE MOST OF THE STRONGER MIDDLE TO UPPER
LEVEL DYNAMICS ARE LOCATED EAST OVER THE SW NORTH ATLC...THE
FRONT IS EXPECTED TO CONTINUE BECOMING MORE DIFFUSE USHERING IN
A RELATIVELY DRIER AIRMASS IN ITS WAKE ACROSS THE SOUTHERN
FLORIDA PENINSULA THIS AFTERNOON. WITH THE NW FLOW ALOFT...THE
REMAINDER OF THE GULF IS UNDER THE INFLUENCE OF SURFACE HIGH
PRESSURE SETTLING IN OVER THE SE CONUS AND NORTHERN GULF
PROVIDING FOR CLEAR SKIES AND FAIR WEATHER CONDITIONS.

CARIBBEAN SEA...
WITH AN UPPER LEVEL TROUGH OVER THE EASTERN GULF OF MEXICO AND
WEAK MIDDLE TO UPPER LEVEL RIDGING OVER THE NW CARIBBEAN SEA...
THE WESTERN CARIBBEAN IS MOSTLY UNDER THE INFLUENCE OF A SURFACE
TROUGH ANALYZED ALONG 12N82W TO 15N83W TO 18N87W. LOW-LEVEL
MOISTURE CONVERGENCE IS MAXIMIZED ALONG THIS BOUNDARY WITH
SCATTERED SHOWERS AND TSTMS OCCURRING FROM 12N-20N W OF 82W.
MOST OF THIS ACTIVITY IS LOCATED OVER THE OPEN WATERS OF THE
WESTERN CARIBBEAN SEA...HOWEVER A FEW COASTAL SHOWERS ARE NOTED
ALONG THE NICARAGUA AND HONDURAS COASTS. FARTHER EAST...AN UPPER
LEVEL ANTICYCLONIC IS CENTERED NEAR 17N72W AND IS PROVIDING AN
OVERALL DIFFLUENCE ENVIRONMENT FOR THE TROPICAL WAVE ALONG 73W
TO FLOURISH CONVECTIVELY THIS AFTERNOON. A LARGE AREA OF
SCATTERED SHOWERS AND TSTMS ARE FOCUSED IN THE VICINITY OF THE
TROPICAL WAVE AS IT IMPACTS MUCH OF THE CENTRAL CARIBBEAN...
INCLUDING PORTIONS OF THE ABC ISLANDS AND SOUTHERN HISPANIOLA.
DEVELOPMENT OF ORGANIZED DEEP CONVECTION AND THE FORMATION OF A
CONSOLIDATED LOW LEVEL CIRCULATION CENTER WILL BE SLOW TO OCCUR
OVER THE NEXT FEW DAYS AS MANY OF THE GLOBAL MODELS SUGGEST A
RATHER BROAD AREA OF LOW PRESSURE ACROSS THE CENTRAL AND WESTERN
CARIBBEAN INTO MID-WEEK.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH IS OVER THE EASTERN CONUS THAT
SUPPORTS A COLD FRONT EXTENDING INTO THE DISCUSSION AREA NEAR
32N75W SW TO THE FLORIDA PENINSULA NEAR 28N80W AND INTO THE SE
GULF OF MEXICO. WATER VAPOR IMAGERY INDICATES THE STRONGEST
DYNAMIC ENERGY HAS PUSHED OFFSHORE INTO THE SW NORTH ATLC AND
ALONG WITH THE COLD FRONT CONTINUES TO SUPPORT SCATTERED SHOWERS
AND TSTMS FROM 26N TO BEYOND 32N BETWEEN 68W AND THE FRONT.
ISOLATED SHOWERS LINGER TO THE SOUTH OF THIS AREA FROM 22N-26N
BETWEEN 73W-79W AS A PRE-FRONTAL SURFACE TROUGH EXTENDS FROM THE
NW BAHAMAS TO WESTERN CUBA. FARTHER EAST...MOST OF THE REMAINDER
OF THE CENTRAL AND EASTERN ATLC...OUTSIDE OF THE TROPICAL WAVES
MENTIONED ABOVE...IS INFLUENCED BY A SURFACE RIDGE THAT IS
STRETCHED THIN IN AN EAST-WEST ORIENTATION AND ANCHORED BY A
1021 MB HIGH CENTERED NEAR 30N34W. A FRONTAL BOUNDARY IS LOCATED
TO THE NORTH OF THIS RIDGE ALONG 34N/35N AND IS EXPECTED TO
CONTINUE A GRADUAL SOUTHWARD MOVEMENT AS AN UPPER LEVEL
SHORTWAVE TROUGH CURRENTLY NEAR 33N42W PROGRESSES E-SE OVER THE
NE ATLC DISCUSSION WATERS DURING THE NEXT 24 TO 36 HOURS.

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

$$
HUFFMAN




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