[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 102339
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU OCT 10 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...
A 1008 MB LOW IS CENTERED NEAR 10N33W AND REMAINS EMBEDDED
WITHIN THE MONSOON TROUGH. THE LOW IS THE FOCAL POINT OF A
BROADER MONSOONAL GYRE WITH INFLUENCE FROM 08N-15N BETWEEN 29W-
43W. THE GYRE CONTINUES TO LIE BENEATH THE WESTERN PERIPHERY OF
AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED NEAR 12N25W
PROVIDING AMPLE UPPER LEVEL DIFFLUENCE FOR WIDELY SCATTERED
MODERATE CONVECTION FROM 09N-14N BETWEEN 29W-41W...AND ISOLATED
MODERATE CONVECTION ELSEWHERE FROM 06N-16N BETWEEN 28W-41W.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 12N53W TO 21N49W MOVING W AT 10-15
KT. THE WAVE REMAINS WITHIN WEAK SURFACE TO 700 MB TROUGHING
BETWEEN 47W-56W WHILE AT THE SAME TIME INTERACTING WITH AN UPPER
LEVEL TROUGH AXIS EXTENDING FROM 24N41W TO 11N55W. ISOLATED
MODERATE CONVECTION IS WITHIN 90 NM EITHER SIDE OF A LINE FROM
12N43W TO 19N48W.

TROPICAL WAVE EXTENDS FROM 10N77W TO 19N77W MOVING W AT 10 KT.
THE WAVE LIES WITHIN BROAD SURFACE TO 700 MB TROUGHING OVER THE
WESTERN CARIBBEAN SEA AND FALLS BENEATH THE BASE OF AN UPPER
LEVEL TROUGH AXIS NEAR 17N81W. LOW-LEVEL MOISTURE CONVERGENCE
ALONG WITH MAXIMUM UPPER LEVEL DIFFLUENCE IS GENERATING
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION FROM 07N-12N
BETWEEN 75W-80W. SCATTERED MODERATE CONVECTION IS FROM 12N-19N
BETWEEN 76W-84W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 11N15W TO
06N20W TO 11N29W TO 09N42W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 09N42W TO 11N52W TO 09N60W. ASIDE FROM THE
CONVECTION ASSOCIATED WITH THE SPECIAL FEATURES LOW AND TROPICAL
WAVE...ISOLATED MODERATE CONVECTION IS FROM 02N-09N BETWEEN 17W-
29W.

...DISCUSSION...

GULF OF MEXICO...
THE GULF BASIN IS PRIMARILY UNDER THE INFLUENCE OF A MIDDLE TO
UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER EAST-CENTRAL
MEXICO NEAR 21N97W THAT EXTENDS A RIDGE AXIS NORTH-NORTHEASTWARD
OVER THE LOWER AND MIDDLE MISSISSIPPI RIVER VALLEY THIS EVENING.
WATER VAPOR IMAGERY INDICATES A VERY DRY AND STABLE ATMOSPHERE
AS THE RESULT OF WEST TO NORTHWESTERLY FLOW ALOFT. PROJECTING
THESE CONDITIONS TO THE SURFACE...A SURFACE RIDGE ANCHORED OVER
THE SE CONUS STRETCHES SOUTHWARD OVER MUCH OF THE BASIN
PROVIDING LIGHT ANTICYCLONIC WINDS...MOSTLY CLEAR SKIES...AND
FAIR CONDITIONS. AN EXITING AND DISSIPATING COLD FRONT LINGERS
ACROSS THE FLORIDA STRAITS GENERATING A FEW ISOLATED SHOWERS AND
TSTMS S OF 24N E OF 83W. ALSO...W OF 90W...EAST-SOUTHEASTERLY
WINDS IN THE RANGE OF 10-15 KT ARE EXPECTED TO GRADUALLY VEER
MORE SOUTHEASTERLY BY FRIDAY MORNING WITH MOIST LOW-LEVEL RETURN
FLOW GENERATING ISOLATED SHOWERS S OF 26N W OF 92W THROUGH THE
OVERNIGHT PERIOD.

CARIBBEAN SEA...
THE BASE OF AN UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR
IMAGERY OVER A PORTION OF THE NW CARIBBEAN PROVIDING MUCH OF THE
WESTERN CARIBBEAN IN A FAVORABLE UPPER LEVEL DIFFLUENT FLOW
PATTERN THIS EVENING. THIS UPPER LEVEL PATTERN ALONG WITH THE
PRESENCE OF A TROPICAL WAVE ALONG 78W IS GENERATING A LARGE AREA
OF SCATTERED SHOWERS AND TSTMS...SOME STRONG...S OF 20N W OF
76W. THE STRONG CONVECTION IS CURRENTLY OCCURRING ACROSS
NORTHERN COLOMBIA AND EASTERN PANAMA AND LIKELY ENHANCED DUE TO
THE CLOSE PROXIMITY OF THE MONSOON TROUGH AXIS EXTENDING ALONG
09N/10N BETWEEN 75W-86W. FARTHER EAST...THE OVERALL UPPER LEVEL
DIFFLUENT REGIME CONTINUES TO PROVIDE INCREASED CLOUDINESS AND
PRECIPITATION FOR THE EASTERN CARIBBEAN N OF 16N. WHILE DAYTIME
HEATING AND INSTABILITY HAS INITIATED SCATTERED SHOWERS AND
TSTMS ACROSS HISPANIOLA AND PUERTO RICO...ISOLATED SHOWERS AND
TSTMS STRETCH WELL NORTHWARD INTO THE SW NORTH ATLC AHEAD OF A
COLD FRONT CURRENTLY EXTENDING FROM OFFSHORE OF THE CAROLINAS TO
THE BAHAMAS AND FLORIDA STRAITS. A VERY BROAD AND WEAK SURFACE
PRESSURE GRADIENT EXISTS BETWEEN 60W-80W AND LENDS ITSELF ALONG
WITH THE UPPER LEVEL DIFFLUENCE TO OVERALL LIFT...CLOUDINESS...
AND WIDELY SCATTERED SHOWER ACTIVITY. FINALLY...E-SE TRADES
CONTINUE TO USHER IN LOW-LEVEL MOISTURE AND ISOLATED SHOWER
ACTIVITY E OF 70W WITH THE HIGHEST CONCENTRATION IN THE VICINITY
OF 14N65W.

HISPANIOLA...
CURRENTLY MIDDLE TO LOW-LEVEL MOISTURE...PEAK HEATING...AND
INSTABILITY ARE GENERATING SCATTERED SHOWERS AND TSTMS ACROSS
HISPANIOLA IN AN AREA OF OVERALL DIFFLUENCE ALOFT OVER THE
REGION SPANNING THE EASTERN CARIBBEAN AND THE SW NORTH ATLC.
THIS MOISTURE STRETCHES EASTWARD TO 60W AND IS EXPECTED TO
REMAIN IN PLACE OVER THE NEXT FEW DAYS WITH MAXIMUM AREAL
COVERAGE OF CONVECTIVE ACTIVITY OCCURRING DURING THE AFTERNOON
AND EVENING HOURS.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL LOW IS NOTED ON WATER VAPOR IMAGERY
CENTERED OVER THE MID-ATLC STATES NEAR 39N78W. THE TROUGH
SUPPORTS A 1007 MB LOW CENTERED NEAR 36N75W WITH A COLD FRONT
EXTENDING SE FROM THE LOW TO 32N72W THEN SOUTH-SOUTHWEST TO
28N74W TO 24N80W. ASIDE FROM THE LOW AND FRONTAL BOUNDARY...MUCH
OF THE SW NORTH ATLC FALLS UNDER A VERY WEAK SURFACE PRESSURE
GRADIENT WITH LOWER PRESSURE GENERALLY BETWEEN 60W-80W. WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING WITHIN 150 NM
EITHER SIDE OF THE FRONT...BUT ARE ALSO OCCURRING FROM 18N-32N
BETWEEN 58W-80W DUE TO THE OVERALL BROAD SURFACE TROUGHING AND
DIFFLUENCE ALOFT. EVENTUALLY BY EARLY SATURDAY MOST OF THE
SURFACE TROUGHING SHIFTS NORTH OF THE DISCUSSION AREA WITH HIGH
PRESSURE RIDGING BUILDING IN FROM BOTH THE EAST ACROSS THE
CENTRAL ATLC AND THE WEST FROM THE NE GULF OF MEXICO. UNTIL
THEN...CONDITIONS ARE EXPECTED TO REMAIN RATHER UNSETTLED WITH
SHOWER AND TSTM ACTIVITY. FARTHER EAST...A SURFACE RIDGE
INFLUENCES THE CENTRAL ATLC N OF 23N BETWEEN 30W-60W ANCHORED BY
A 1021 MB HIGH CENTERED NEAR 31N48W. THE SURFACE RIDGING
STRETCHES ACROSS THE EASTERN ATLC...HOWEVER IS SLIGHTLY WEAKER
DUE TO A DISSIPATING COLD FRONTAL BOUNDARY EXTENDING FROM 32N25W
TO 28N29W. NO SIGNIFICANT PRECIPITATION IS OCCURRING ALONG THE
FRONT AT THIS TIME.

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

$$
HUFFMAN


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