[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 292349
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU AUG 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...
TROPICAL WAVE EXTENDS FROM 09N16W TO 20N13W MOVING W AT 10-15
KT. A 1008 MB LOW IS CENTERED ALONG THE WAVE AXIS NEAR 15N15W.
ALTHOUGH THIS WAVE HAS YET TO FULLY EMERGE OFF THE COAST OF WEST
AFRICA...IT DISPLAYS PLENTY OF SURFACE TO 700 MB VORTICITY WITH
A MAXIMUM IN THE VICINITY OF THE SURFACE LOW AND AREAS TO THE
SOUTH ALONG THE WAVE AXIS. SCATTERED MODERATE CONVECTION IS
OCCURRING FROM 10N-12N BETWEEN 14W-18W...WITH ISOLATED MODERATE
CONVECTION ELSEWHERE FROM 09N-18N BETWEEN 10W-19W.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 11N46W TO 19N45W MOVING W AT 10-15
KT. BROAD LOW-LEVEL CYCLONIC TURNING IS EVIDENT IN SATELLITE
IMAGERY ABOUT THE WAVE AXIS WITH A 700 MB RELATIVE VORTICITY
MAXIMUM CENTERED IN THE VICINITY OF 15N46W. TOTAL PRECIPITABLE
WATER IMAGERY ALSO SHOWS MAXIMUM VALUES SURROUNDING THE AXIS
FROM 13N-20N BETWEEN 37W-51W. CONVECTION WITH THE WAVE HAS
INCREASED OVER THE PAST 24 HOURS WITH WIDELY SCATTERED MODERATE
CONVECTION OCCURRING WITHIN 90 NM EITHER SIDE OF A LINE FROM
13N33W TO 18N45W NEAR THE NORTHERN EXTENT OF THE WAVE AXIS.

TROPICAL WAVE EXTENDS FROM 15N64W TO 22N61W MOVING W-NW AT 15-20
KT. OVERALL THE WAVE COINCIDES WITH WEAK SURFACE TO 700 MB LOW-
LEVEL TROUGHING...HOWEVER SOME OF THE VORTICITY LOCATED NEAR THE
SOUTHERN EXTENT OF THE WAVE AXIS 24 HOURS AGO HAS BEEN LEFT
BEHIND TO THE SOUTHEAST AS THE WAVE CONTINUES ITS W-NW MOVEMENT.
WHILE A FEW SHOWERS AND TSTMS REMAIN TO THE EAST OF THE LESSER
ANTILLES...ISOLATED MODERATE CONVECTION IS OCCURRING FROM 19N-
23N BETWEEN 57W-65W.

TROPICAL WAVE EXTENDS FROM 08N96W TO 19N94W MOVING W AT 10-15
KT. WHILE MOST OF THE WAVE LIES IN THE EAST PACIFIC REGION...
OVERALL THE WAVE AXIS COINCIDES WITH BROAD 700 MB TROUGHING S OF
23N BETWEEN 89W-98W. WIDELY SCATTERED MODERATE CONVECTION IS
FROM 15N-19N BETWEEN 92W-96W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 14N17W TO
11N29W TO 10N34W TO 11N43W. ISOLATED MODERATE CONVECTION IS FROM
05N-12N BETWEEN 21W-33W.

...DISCUSSION...

GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL LOW IS CENTERED OVER THE FLORIDA KEYS
NEAR 25N82W THAT IS PROVIDING FOR A FEW ISOLATED SHOWERS THIS
EVENING OVER THE FLORIDA PENINSULA AND ADJACENT COASTAL WATERS
IN THE VICINITY OF 27N83W. WATER VAPOR IMAGERY INDICATES MOST OF
THE GULF IS HOWEVER UNDER A FAIRLY DRY AND STABLEE AIRMASS. THIS
IS FURTHER SUPPORTED BY OVERALL SURFACE RIDGING MAINLY NOTED N
OF 22N. ONE COMPROMISE TO THE RIDGE IS A WEAK SURFACE TROUGH
ANALYZED FROM 24N90W TO 28N90W. WHILE NO SIGNIFICANT DEEP
CONVECTION IS NOTED WITH THE TROUGH...A SUBTLE WIND SHIFT ACROSS
THE CENTRAL GULF IS APPARENT IN SHIP OBSERVATIONS...BUOYS...AND
A FEW OF THE OFFSHORE OIL PLATFORMS. ACROSS THE SW GULF..THE
NORTHERN EXTENT OF A TROPICAL WAVE IS ALONG 94W AND CONTINUES TO
PROVIDE FOCUS FOR ISOLATED SHOWERS AND TSTMS S OF 19N BETWEEN
93W-95W. LOOKING AHEAD...THE GULF IS EXPECTED TO REMAIN FAIRLY
TRANQUIL WITH DRY AIR AND STABILITY ALOFT...AND A SURFACE RIDGE
ANCHORED OVER EASTERN PORTIONS THROUGH THE UPCOMING WEEKEND. THE
RIDGE AXIS IS FORECAST ALONG 26N/27N WITH GENERALLY LIGHT E-SE
WINDS SOUTH OF THE AXIS.

CARIBBEAN SEA...
AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER THE
WESTERN CARIBBEAN NEAR 18N78W THAT IS PROVIDING PRIMARILY A
MOIST AND DIFFLUENT AIRMASS W OF 80W AND A DRY AND SUBSIDENT
AIRMASS FOR THE CENTRAL AND EASTERN CARIBBEAN THIS EVENING.
WHILE THE SURFACE PRESSURE GRADIENT REMAINS RELATIVELY WEAK
ACROSS THE WESTERN CARIBBEAN...THE UPPER LEVEL RIDGE AXIS
EXTENDS WEST-NORTHWEST TO OVER THE YUCATAN PENINSULA AND IS
GENERATING SCATTERED SHOWERS AND TSTMS NW OF A LINE FROM COASTAL
NICARAGUA NEAR 12N84W TO JAMAICA NEAR 18N77W TO THE WINDWARD
PASSAGE NEAR 20N74W. PORTIONS OF THIS CONVECTION ARE OCCURRING
OVER INTERIOR AREAS OF CUBA...NICARAGUA...HONDURAS...AND THE
YUCATAN PENINSULA THIS EVENING AND ARE LIKELY ENHANCED DUE TO
THE UPPER LEVEL RIDGING AND ASSOCIATED DIFFLUENCE ALOFT. OVER
THE EASTERN CARIBBEAN...DRY AIR ALOFT DOMINATES S OF 17N E OF
80W WITH VERY LITTLE SIGNIFICANT WEATHER OCCURRING THIS EVENING
OVER THIS AREA. A TROPICAL WAVE CLIPS THE NE CARIBBEAN FROM
15N64W TO 22N61W AND IS PROVIDING FOCUS FOR ISOLATED SHOWERS
FROM 15N-19N BETWEEN 60W-72W...INCLUDING PUERTO RICO...AND
PORTIONS OF HISPANIOLA. THE TROPICAL WAVE IS FORECAST TO
CONTINUE W-NW INCREASING PROBABILITY FOR PRECIPITATION OVER THE
NEXT 24 TO 36 HOURS ACROSS THE GREATER ANTILLES AND ADJACENT
COASTAL WATERS.

HISPANIOLA...
CURRENTLY A FEW ISOLATED SHOWERS AND TSTMS REMAIN ACROSS
PORTIONS OF THE ISLAND AND THIS ACTIVITY IS EXPECTED TO
GRADUALLY DIMINISH OVER THE NEXT FEW HOURS. WATER VAPOR IMAGERY
INDICATES AN UPPER LEVEL ANTICYCLONE IS CENTERED WEST OF THE
ISLAND NEAR 18N78W THAT IS PROVIDING THE CENTRAL AND EASTERN
CARIBBEAN WITH RELATIVELY DRY AND STABLE AIR ALOFT. HOWEVER
MOISTURE CONTINUES TO ADVECT SOUTHEASTWARD FROM THE SW NORTH
ATLC ACROSS THE GREATER ANTILLES AND THE APPROACH OF A TROPICAL
WAVE OVER THE NEXT 24 TO 48 HOURS WILL INCREASE MOISTURE AND
CONVECTIVE ACTIVITY ACROSS HISPANIOLA ON FRIDAY AND SATURDAY.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL LOW IS CENTERED OVER THE FLORIDA KEYS
NEAR 25N82W THAT SUPPORTS A SURFACE TROUGH EXTENDING FROM 21N79W
TO 25N78W WITH ISOLATED SHOWERS OCCURRING FROM 23N-28N BETWEEN
74W-78W. STRONGER CONVECTION IS LOCATED OVER INTERIOR PORTIONS
OF CUBA E OF 80W THIS EVENING. FARTHER EAST...OVER THE REMAINDER
OF THE SW NORTH ATLC...MID-LEVEL TROUGHING IS NOTED ON WATER
VAPOR IMAGERY BETWEEN 60W-80W AND IS PROVIDING AN OVERALL
UNSTABLE ENVIRONMENT. WITH A COLD FRONT EXTENDING ALONG 34N
PROGRESSING OFF THE CAROLINA COAST AND THE ASSOCIATED SURFACE
TROUGHING DIPPING SOUTHWARD TO 30N AND A TROPICAL WAVE ALONG 63W
NE OF PUERTO RICO...WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS
COVER THE AREA FROM 20N-32N BETWEEN 57W-74W. THE MORE INTENSE
CONVECTION IS LOCATED GENERALLY N OF 30N IN AN AREA OF MAXIMUM
MIDDLE TO UPPER LEVEL DIFFLUENCE SOUTHEAST OF THE COLD FRONT.
ASIDE FROM THE TROPICAL WAVE PROGRESSING WESTWARD S OF 20N ALONG
46W...A SURFACE RIDGE INFLUENCES THE REMAINDER OF THE CENTRAL
AND EASTERN ATLC ANCHORED BY A 1025 MB HIGH CENTERED NEAR
34N44W. THE ONLY COMPROMISE TO THE RIDGE IS A SURFACE TROUGH
ANALYZED FROM 34N35W TO A 1020 MB LOW CENTERED NEAR 30N38W. THIS
WEAK LOW REMAINS A SURFACE REFLECTION OF AN UPPER LEVEL LOW
CENTERED NEAR 29N36W. ISOLATED SHOWERS ARE OCCURRING FROM 29N-
32N BETWEEN 35W-38W.

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

$$
HUFFMAN


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