[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121118
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT OCT 12 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...
A 1006 MB LOW IS CENTERED NEAR 11N41W AND REMAINS EMBEDDED
WITHIN THE MONSOON TROUGH AXIS. BROAD LOW-LEVEL CYCLONIC FLOW
SURROUNDS THE LOW FROM 08N-16N BETWEEN 28W-46W WITH A RELATIVE
VORTICITY MAXIMUM INDICATED ON THE GLOBAL MODEL 700 MB LEVEL
NEAR 12N40W. SCATTERED MODERATE CONVECTION IS FROM 09N-14N
BETWEEN 35W-47W. THE LOW PRESSURE AREA REMAINS IN A FAVORABLE
AREA OF TROPICAL CYCLONE FORMATION...HOWEVER WITHIN THE NEXT 24
TO 36 HOURS SOUTHWESTERLY UPPER LEVEL WIND SHEAR WILL INCREASE
OVER THE LOW AS IT MOVES W-NW AT 10 KT.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 14N62W TO 21N62W MOVING W AT 10-15
KT. THE WAVE LIES BENEATH THE WESTERN PERIPHERY OF AN UPPER
LEVEL LOW CENTERED TO THE EAST NEAR 16N56W. WATER VAPOR IMAGERY
INDICATES VERY DRY AIR ALOFT ON THE WESTERN SIDE OF THIS UPPER
LOW RESULTING IN AN OVERALL LACK OF SIGNIFICANT DEEP CONVECTION
IN THE VICINITY OF THE WAVE AXIS. ISOLATED MODERATE CONVECTION
IS HOWEVER OCCURRING FROM 17N-21N BETWEEN 56W-60W AND IS LIKELY
MORE ASSOCIATED WITH THE UPPER LEVEL LOW DYNAMICS.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 18N16W TO
08N25W TO 06N30W TO 11N41W TO 08N48W. THE INTERTROPICAL
CONVERGENCE ZONE AXIS EXTENDS FROM 08N48W TO 07N58W. ASIDE FROM
CONVECTION ASSOCIATED WITH THE SPECIAL FEATURES LOW...SCATTERED
MODERATE CONVECTION IS FROM 08N-12N BETWEEN 22W-28W...AND
ISOLATED MODERATE CONVECTION IS FROM 03N-08N BETWEEN 23W-31W.

...DISCUSSION...

GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED
OVER CENTRAL MEXICO NEAR 20N100W THAT IS PROVIDING THE GULF
BASIN WITH NORTHWEST TO NORTHERLY FLOW ALOFT THIS MORNING. WATER
VAPOR IMAGERY INDICATES THE FLOW IS MOSTLY DRY AIR AND VERY
STABLE RESULTING IN MOSTLY CLEAR SKIES AND FAIR CONDITIONS AT
THE SURFACE. A 1018 MB HIGH CENTERED ALONG THE FLORIDA PANHANDLE
COAST NEAR 30N87W FURTHER PROMOTES THE FAIR CONDITIONS WITH ONLY
A FEW ISOLATED SHOWERS OCCURRING ACROSS THE NW GULF FROM 26N-28N
BETWEEN 91W-96W AS SOUTHEASTERLY RETURN FLOW CONTINUES TO
CONVERGE ACROSS THIS AREA. SURFACE RIDGING IS EXPECTED TO REMAIN
ACROSS THE GULF THROUGH LATE WEDNESDAY WHEN THE NEXT FRONTAL
BOUNDARY IS FORECAST TO EMERGE OFF THE TEXAS GULF COAST.

CARIBBEAN SEA...
AN UPPER LEVEL LOW IS CENTERED NEAR 18N79W AND EXTENDS A TROUGH
AXIS SOUTHWARD ALONG 80W TO A BASE OVER THE SW CARIBBEAN NEAR
11N81W. WEST OF THE TROUGH AXIS...WATER VAPOR IMAGERY INDICATES
VERY DRY AND STABLE AIR WITHIN NORTHERLY FLOW PROVIDING FOR
RELATIVELY QUIET CONDITIONS THIS MORNING N OF 17N W OF 78W.
HOWEVER S OF 17N...THE UPPER LEVEL LIFTING DYNAMICS CONTINUE TO
GENERATE SCATTERED SHOWERS AND ISOLATED TSTMS OFF THE HONDURAS
AND NICARAGUA COASTS FROM 13N-17N BETWEEN 82W-86W. WITH A
RELATIVELY STRONG UPPER LEVEL LOW CENTERED OVER THE REMAINDER OF
THE WESTERN CARIBBEAN...ISOLATED SHOWERS AND TSTMS ARE OCCURRING
NEAR THE BASE OF THE UPPER LEVEL TROUGH AND IN THE AREA OF
MAXIMUM MIDDLE TO UPPER LEVEL DIFFLUENCE EAST OF THE TROUGH
AXIS. ISOLATED SHOWERS AND TSTMS ARE OCCURRING WITHIN 240 NM
EITHER SIDE OF A LINE FROM 11N79W TO 20N74W. FINALLY...A WEAK
TROPICAL WAVE IS ANALYZED ALONG 62W IMPACTING THE LESSER
ANTILLES THIS MORNING WITH MUCH OF THE PRECIPITATION ASSOCIATED
WITH THE WAVE REMAINING TO THE EAST-NORTHEAST OF THE LEEWARD
ISLANDS AT THIS TIME. AS THE WAVE MOVES WESTWARD...INCREASED LOW-
LEVEL MOISTURE...CLOUDINESS...AND PRECIPITATION IS EXPECTED FOR
THE ISLANDS DURING THE NEXT 24 TO 36 HOURS.

HISPANIOLA...
CURRENTLY THE ISLAND FALLS WITHIN AN AREA OF MIDDLE TO UPPER
LEVEL DIFFLUENCE NOTED TO THE EAST OF AN UPPER LEVEL TROUGH
ALONG 80W. THE ADVECTION OF MOISTURE FROM THE EAST PACIFIC NEAR
THE BASE OF THE TROUGH AND MOISTURE FROM NORTHERN SOUTH AMERICA
NORTHWARD ACROSS THE CENTRAL CARIBBEAN SEA AND SW NORTH ATLC IS
PROVIDING FOR ISOLATED SHOWERS AND TSTMS THIS MORNING. AS THE
TROUGH ALONG 80W IS FORECAST TO EVENTUALLY MOVE SOUTHWEST BY
LATE SUNDAY INTO MONDAY...UNTIL THEN HISPANIOLA WILL LIKELY
REMAIN IN AN UPPER LEVEL DIFFLUENT PATTERN WITH INCREASED
PROBABILITY OF ISOLATED SHOWERS AND TSTMS. OF COURSE AS ALWAYS
WITH PEAK DAYTIME HEATING AND INSTABILITY...MAXIMUM AREAL
COVERAGE OF CONVECTION IS LIKELY TO OCCUR IN THE AFTERNOON AND
EVENING HOURS.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL LOW IS CENTERED OVER THE MID-ATLC STATES
NEAR 37N76W THAT SUPPORTS AN OCCLUDED 1011 MB LOW CENTERED
OFFSHORE NEAR 38N75W. A STATIONARY FRONT EXTENDS FROM THE LOW
PRESSURE SYSTEM INTO THE DISCUSSION AREA NEAR 32N69W TO 26N74W
AND BECOMES SURFACE TROUGHING FROM 27N73W TO 21N74W. PLENTY OF
MIDDLE TO UPPER LEVEL MOISTURE ADVECTION IS NOTED ON WATER VAPOR
IMAGERY EAST OF THE UPPER LEVEL TROUGH AXIS WITH WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS OCCURRING FROM 18N-32N
BETWEEN 62W-77W...FOCUSED IN THE VICINITY OF THE SURFACE
BOUNDARIES. FARTHER EAST...THE REMAINDER OF THE CENTRAL AND
EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED
BY A 1023 MB HIGH CENTERED NEAR 35N37W AND A 1020 MB HIGH
CENTERED NEAR 31N18W. BRIDGING BOTH OF THESE HIGH CENTERS IS A
DISSIPATING STATIONARY FRONT ANALYZED FROM 32N27W TO 29N40W.
ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE
FRONT.

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

$$
HUFFMAN


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