[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 210554
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED AUG 21 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 10N34W TO 16N32W TO 21N28W MOVING W
AT 10 KT. A 1010 MB LOW IS CENTERED ON THE SOUTHERN EXTENT OF
THE WAVE AXIS NEAR 11N34W AND REMAINS THE FOCAL POINT FOR A
BROAD AND ENLONGATED MONSOONAL GYRE INFLUENCING THE TROPICAL
ATLC FROM 08N-19N BETWEEN 22W-47W. NO SIGNIFICANT DEEP
CONVECTION IS OCCURRING IN THE VICINITY OF THE WAVE.

TROPICAL WAVE EXTENDS FROM 11N72W TO 20N72W MOVING W AT 10 KT.
THE WAVE REMAINS WITHIN LOW-LEVEL...700 MB...TROUGHING LOCATED
ACROSS THE CENTRAL CARIBBEAN SEA WITH TOTAL PRECIPITABLE WATER
IMAGERY INDICATING A LOCAL MAXIMUM FROM 11N-20N BETWEEN 66W-73W.
ISOLATED MODERATE CONVECTION IS FROM 13N-19N BETWEEN 67W-72W.

TROPICAL WAVE EXTENDS FROM 18N93W TO 27N92W MOVING W AT 15 KT.
THE WAVE CONTINUES ITS WESTWARD MOVEMENT ON THE SOUTHWESTERN
PERIPHERY OF A RIDGE ANCHORED IN THE SW NORTH ATLC REGION. WHILE
SOME ENERGY ASSOCIATED WITH THE WAVE CONTINUE TO SHAVE NORTH-
NORTHEASTWARD OVER THE NORTH-CENTRAL GULF OF MEXICO...THE WAVE
IS EXPECTED TO DISSIPATED IN THE NEXT 24 TO 36 HOURS AS IT MOVES
INLAND OVER INTERIOR MEXICO. ISOLATED MODERATE CONVECTION IS
FROM 26N-29N BETWEEN 88W-91W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 16N17W TO
16N21W TO 09N34W TO 06N44W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 06N44W TO 06N54W. ISOLATED MODERATE CONVECTION
IS FROM 11N-14N BETWEEN 21W-24W...AND FROM 07N-09N BETWEEN 33W-
40W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL LOW IS CENTERED OVER NORTHERN MEXICO NEAR 25N102W
AND IS PROVIDING ADVECTION OF MOISTURE ACROSS CENTRAL MEXICO AND
INTO THE WESTERN GULF. WHILE NO SURFACE FORCING FEATURE IS
PRESENT...AMPLE MIDDLE TO UPPER LEVEL DYNAMICS ARE IN PLACE TO
GENERATE A ISOLATED SHOWERS AND TSTMS S OF 26N W OF 95W THIS
EVENING. TO THE EAST...A TROPICAL WAVE IS ALONG 92W AND EXTENDS
WEAK SURFACE TROUGHING FROM SOUTHEASTERN LOUISIANA ALONG THE
WAVE AXIS TO SOUTHERN MEXICO. THIS RELATIVELY NARROW AREA OF
CYCLONIC TURNING IN THE LOWER LEVELS OF THE ATMOSPHERE IS
GENERATING ISOLATED SHOWERS AND TSTMS ACROSS THE WESTERN YUCATAN
PENINSULA AND OVER THE NORTH-CENTRAL GULF WATERS FROM 22N-30N
BETWEEN 87W-92W. FINALLY...OVER THE EASTERN GULF...NORTHERLY
UPPER LEVEL FLOW DOMINATES ON THE WESTERN PERIPHERY OF AN UPPER
LEVEL LOW CENTERED OVER THE NW CARIBBEAN SEA NEAR 20N84W THAT
EXTENDS A TROUGH AXIS NORTHWARD OVER THE SOUTHERN FLORIDA
PENINSULA TO 28N80W. OVERALL UPPER LEVEL CYCLONIC TURNING...A
MID-LEVEL VORTICITY MAXIMUM IN THE VICINITY OF 25N85W...AND LACK
OF ANY STRONG PRESSURE GRADIENT AT THE SURFACE IS GENERATING
WIDELY SCATTERED SHOWERS AND ISOLATED SHOWERS THIS EVENING E OF
87W...INCLUDING THE FLORIDA STRAITS. LOOKING AHEAD...GENERALLY
EAST-SOUTHEAST WINDS ARE EXPECTED TO PREVAIL THROUGH THE
REMAINDER OF THE WEEK AS A SURFACE RIDGE CONTINUES TO ANCHOR
ITSELF IN THE SW NORTH ATLC WATERS NEAR 32N72W.

CARIBBEAN SEA...
AN UPPER LEVEL LOW IS CENTERED OVER THE NW CARIBBEAN NEAR 20N84W
THAT CONTINUES TO GENERATE ISOLATED SHOWERS AND TSTMS N OF 19N
BETWEEN 75W-86W...INCLUDING THE CAYMAN ISLANDS AND CUBA THIS
EVENING. OTHERWISE...TO THE SOUTHEAST OF THE UPPER LEVEL
LOW...SOUTH-SOUTHWESTERLY FLOW ALOFT DOMINATES ACROSS THE SW
CARIBBEAN. LOW-LEVEL MOISTURE CONVERGENCE ALONG WITH THE
DIFFLUENT ENVIRONMENT PRESENT OVER THE REGION IS GENERATING
WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS S OF 15N BETWEEN 79W-
84W. CONVECTION STRETCHES SOUTH OF THIS AREA ACROSS PORTIONS OF
PANAMA AND COSTA RICO AS THE MONSOON TROUGH AXIS EXTENDS ALONG
09N FROM NORTHERN COLOMBIA INTO THE EAST PACIFIC REGION. ACROSS
THE CENTRAL CARIBBEAN...A TROPICAL WAVE IS ALONG 72W AND REMAINS
EMBEDDED WITHIN BROAD LOW-LEVEL TROUGHING. WITH DEEP TROPICAL
MOISTURE NOTED ON TOTAL PRECIPITABLE WATER IMAGERY...ISOLATED
SHOWERS AND TSTMS ARE OCCURRING S OF 20N BETWEEN 65W-73W...AND S
OF 12N BETWEEN 69W-75W. THE WAVE IS EXPECTED TO CONTINUE MOVING
WESTWARD AND INCREASE PRECIPITATION CHANCES FOR THE WESTERN
CARIBBEAN OVER THE NEXT 24 TO 48 HOURS. FINALLY...A WEAK SURFACE
TROUGH FROM 10N-15N ALONG 57W CONTINUES TO PROVIDE ISOLATED
SHOWERS AND TSTMS FOR THE LESSER ANTILLES S OF 16N. THIS AREA OF
CONVECTION IS LIKELY ENHANCED DUE TO MARGINAL MIDDLE TO UPPER
LEVEL DIFFLUENCE LOCATED OVER THE TROPICAL ATLC AND EASTERN
CARIBBEAN.

HISPANIOLA...
CURRENTLY EARLIER EVENING CONVECTION CONTINUES TO DIMINISH WITH
ONLY A FEW REMAINING ISOLATED SHOWERS OCCURRING ACROSS THE
ISLAND. WESTERLY FLOW ALOFT REMAINS OVER THE ISLAND ON THE
NORTHERN PERIPHERY OF AN UPPER LEVEL ANTICYCLONIC CIRCULATION
CENTERED OVER THE CENTRAL CARIBBEAN THIS EVENING. WITH MARGINAL
MIDDLE TO UPPER LEVEL LIFT PRESENT AND A TROPICAL WAVE ALONG
72W...ISOLATED SHOWERS AND TSTMS ARE EXPECTED OVER THE NEXT 24
TO 36 HOURS WITH STRONGER SCATTERED CONVECTION EXPECTED TO
INITIATE DURING THE AFTERNOON HOURS DUE TO PEAK DAYTIME HEATING
AND INSTABILITY. ANY ACTIVITY THAT FORMS WILL LIKELY LAST INTO
THE EVENING HOURS AND DIMINISH THEREAFTER.

ATLANTIC OCEAN...
A WEAK UPPER LEVEL LOW IS CENTERED OVER THE SOUTHERN FLORIDA
PENINSULA NEAR 28N81W THAT CONTINUES TO PRODUCE ENHANCEMENT FOR
WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS OCCURRING S OF 29N W
OF 74W ACROSS PORTIONS OF THE SW NORTH ATLC. THIS ACTIVITY
REMAINS ON THE SOUTHWESTERN PERIPHERY OF A SURFACE RIDGE
ANCHORED BY A 1021 MB HIGH CENTERED WEST OF BERMUDA NEAR 32N69W.
THE SURFACE HIGH IS LARGELY SUPPORTED BY A MIDDLE TO UPPER LEVEL
ANTICYCLONIC CIRCULATION CENTERED NEARLY OVERHEAD NEAR 31N69W.
FARTHER EAST...AN UPPER LEVEL LOW IS CENTERED NEAR 27N55W WITH A
TROUGH AXIS EXTENDING NORTHEAST TO BEYOND 32N51W AND SOUTHWEST
TO A BASE NEAR 20N67W. MID-LATITUDE MOISTURE CONTINUES TO ADVECT
SOUTHWARD ON THE WESTERN PERIPHERY OF THE LOW PRODUCING ISOLATED
SHOWERES WITHIN 120 NM EITHER SIDE OF A LINE FROM 32N54W TO
28N64W. OTHERWISE...THE REMAINDER OF THE CENTRAL AND EASTERN
ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A
1022 MB HIGH CENTERED SOUTH OF THE AZORES NEAR 35N29W. THE RIDGE
AXIS EXTENDS SOUTHWEST FROM THE HIGH TO NEAR 28N50W.

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

$$
HUFFMAN


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