[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201733
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI SEP 20 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
1715 UTC.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 10N17W TO 17N18W MOVING W AT 10-15
KT. THE WAVE REMAINS EMBEDDED WITHIN THE MONSOON TROUGH AND
COINCIDES WITH A SURFACE TO 700 MB TROUGH AND 700 MB RELATIVE
VORTICITY MAXIMUM IN THE VICINITY OF 14N18W ALONG THE WAVE AXIS.
WIDELY SCATTERED MODERATE CONVECTION IS FROM 05N-12N BETWEEN 14W-
22W...AND FROM 15N-18N BETWEEN 14W-20W.

TROPICAL WAVE EXTENDS FROM 14N34W TO 24N34W MOVING W AT 10-15
KT. TOTAL PRECIPITABLE WATER IMAGERY INDICATES MOST OF THE WAVE
HAS BEEN UNDERCUT BY A RELATIVELY DRIER AIRMASS WHICH CONTINUES
TO LIMIT CONVECTION AT THIS TIME. ISOLATED MODERATE CONVECTION
IS FROM 21N-24N BETWEEN 29W-35W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N16W TO
11N22W TO A 1012 MB LOW NEAR 11N30W TO 08N35W TO 07N43W. THE
INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N43W TO
05N53W. SCATTERED MODERATE CONVECTION IS FROM 04N-16N BETWEEN
25W-33W...AND FROM 05N-09N BETWEEN 33W-41W.

...DISCUSSION...

GULF OF MEXICO...
NORTHERLY UPPER LEVEL FLOW DOMINATES OVER THE GULF BASIN THIS
AFTERNOON BETWEEN AN UPPER LEVEL ANTICYCLONIC CIRCULATION
CENTERED OVER MEXICO NEAR 23N100W AND AN UPPER LEVEL TROUGH AXIS
EXTENDING FROM OVER THE SW NORTH ATLC NEAR 28N77W TO OVER THE
NORTHERN YUCATAN PENINSULA NEAR 21N87W. WATER VAPOR IMAGERY
INDICATES THE AIRMASS USHERED IN ON THE NORTHERLY FLOW REMAINS
RELATIVELY DRY AND STABLE WITH MOSTLY CLEAR SKIES AND FAIR
CONDITIONS NOTED E OF 91W. THE ONLY EXCEPTION TO THE FAIR SKIES
ARE A FEW ISOLATED SHOWERS AND TSTMS OCCURRING WITHIN 90 NM
EITHER SIDE OF A LINE FROM 29N85W TO 25N83W. OTHERWISE...SURFACE
RIDGING EXTENDS SOUTHWARD FROM THE CAROLINAS ACROSS THE FLORIDA
PENINSULA TO THE NORTHWEST CARIBBEAN SEA. FINALLY...ACROSS THE
WESTERN GULF...A 1002 MB LOW IS CENTERED NEAR 22N97W THAT
CONTINUES TO STRUGGLE IN SUSTAINING ANY ORGANIZED CONVECTION AT
THIS TIME. SCATTERED MODERATE CONVECTION IS PRIMARILY OCCURRING
WITHIN 150 NM OF CENTER WITHIN THE SOUTHERN QUADRANT. THE LACK
OF ORGANIZATION IS DUE TO NORTHWESTERLY SHEAR AND A DRIER
AIRMASS LOCATED OVER PORTIONS OF THE EASTERN AND CENTRAL GULF OF
MEXICO. THE GREATEST IMPACT FROM THIS LOW WILL CONTINUE TO BE
LOCALLY HEAVY RAINFALL AT TIMES OVER PORTIONS OF EASTERN AND
SOUTHERN MEXICO THROUGH THE WEEKEND. SOUTHEAST WINDS IN THE
RANGE OF 15 TO 25 KT ARE FORECAST TO CONTINUE THROUGH EARLY
SATURDAY AS THE LOW DRIFTS NORTHWARD TOWARDS THE TEXAS GULF
COAST. THEREAFTER FOR THE REMAINDER OF THE WEEKEND... GLOBAL
MODELS SUGGEST THE LOW WILL BE POSITIONED ACROSS THE NW GULF
WATERS AT THE TAIL END OF A WEAK FRONTAL BOUNDARY DRAPED ALONG
THE GULF COASTAL PLAINS.

CARIBBEAN SEA...
AN UPPER LEVEL RIDGE AXIS EXTENDS ACROSS THE WESTERN CARIBBEAN
FROM OVER HISPANIOLA NEAR 18N71W WESTWARD TO OVER CENTRAL
AMERICA NEAR 14N87W THAT IS PROVIDING AN OVERALL UPPER LEVEL
DIFFLUENT ENVIRONMENT W OF 70W. THIS UPPER LEVEL REGIME ALONG
WITH THE MONSOON TROUGH AXIS ANALYZED ALONG THE SPINE OF CENTRAL
AMERICA FROM NORTHERN COLOMBIA TO GUATEMALA IS GENERATING WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS W OF 75W. THE REMAINDER OF
THE CENTRAL AND EASTERN CARIBBEAN IS UNDER THE INFLUENCE OF A
RELATIVELY DRIER AIRMASS NOTED ON WATER VAPOR IMAGERY...WHICH IS
KEEPING SKIES MOSTLY CLEAR THIS AFTERNOON. A FEW ISOLATED
SHOWERS ARE NOTED HOWEVER SOUTH OF PUERTO RICO NEAR 17N66W AND
ACROSS THE SOUTHERN WINDWARD ISLANDS S OF 13N E OF 63W. LOOKING
AHEAD...A SURFACE TROUGH IS ANALYZED EAST OF THE LESSER ANTILLES
ALONG 55W AND IS EXPECTED TO BEGIN IMPACTING THE ISLANDS BY
EARLY SUNDAY INTO MONDAY WITH INCREASED CLOUDINESS AND
PRECIPITATION.

HISPANIOLA...
CURRENTLY SKIES REMAIN FAIR THIS AFTERNOON...HOWEVER WITH AN
UPPER LEVEL DIFFLUENT ENVIRONMENT NOTED ON WATER VAPOR IMAGERY
ACROSS THE ISLAND STRETCHING WESTWARD OVER THE WESTERN CARIBBEAN
SEA...SCATTERED SHOWER AND TSTM ACTIVITY IS FORECAST TO INITIATE
LATE THIS AFTERNOON AND CONTINUE THROUGH THE EVENING HOURS. THIS
OVERALL SYNOPTIC PATTERN IS EXPECTED TO CHANGE LITTLE OVER THE
NEXT FEW DAYS WITH AFTERNOON AND EARLY EVENING CONVECTION
ANTICIPATED ACROSS THE ISLAND.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL LOW IS CENTERED OVER THE WESTERN NORTH
ATLC NEAR 36N70W THAT EXTENDS A TROUGH AXIS SOUTHWESTWARD TO
31N73W TO 24N82W. THIS TROUGHING SUPPORTS A STATIONARY FRONT
THAT ENTERS THE DISCUSSION AREA NEAR 32N46W EXTENDING W-SW INTO
A 1010 MB LOW CENTERED NEAR 27N64W. A SURFACE TROUGH THEN
EXTENDS W-SW FROM THE LOW TO THE SE BAHAMAS NEAR 23N74W TO THE
COAST OF CENTRAL CUBA NEAR 22N78W. SCATTERED SHOWERS AND TSTMS
ARE OCCURRING WITHIN 180 NM EITHER SIDE OF A LINE FROM 30N59W TO
22N68W WITH WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS
OCCURRING ELSEWHERE WITHIN 120 NM EITHER SIDE OF THE FRONT E OF
57W...AND FROM 20N-25N BETWEEN 69W-81W. TO THE SOUTHEAST...AN
UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 14N57W AND IS PROVIDING
A FAVORABLE UPPER LEVEL DIFFLUENT ENVIRONMENT FOR A 1014 MB LOW
CENTERED NEAR 14N55W. SCATTERED SHOWERS AND WIDELY SCATTERED
TSTMS ARE OCCURRING IN CLOSE PROXIMITY TO THE LOW CENTER FROM
12N-16N BETWEEN 52W-57W. FINALLY...THE REMAINDER OF THE EASTERN
ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A
1026 MB HIGH CENTERED EAST OF THE AZORES NEAR 40N21W.

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

$$
HUFFMAN


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