[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 120547
TWDAT

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

...SPECIAL FEATURES...
A 1008 MB LOW IS CENTERED NEAR 12N40W 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 TO STRONG CONVECTION IS FROM 10N-
14N BETWEEN 35W-45W. 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 ACROSS THE LOW AS IT MOVES W-NW AT 10 KT.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 11N61W TO 22N61W MOVING W AT 15-20
KT. THE WAVE LIES BENEATH THE WESTERN PERIPHERY OF AN UPPER
LEVEL LOW CENTERED TO THE EAST NEAR 17N56W. WATER VAPOR IMAGERY
INDICATES VERY DRY AIR ALOFT ON THE WESTERN SIDE OF THIS UPPER
LOW AND THIS IS RESULTING IN AN OVERALL LACK OF SIGNIFICANT DEEP
CONVECTION IN THE VICINITY OF THE WAVE AXIS. ISOLATED MODERATE
CONVECTION IS HOWEVER OCCURRING FROM 16N-20N BETWEEN 54W-60W AND
IS LIKELY MORE ASSOCIATED WITH THE UPPER LEVEL LOW DYNAMICS.

TROPICAL WAVE EXTENDS FROM 11N83W TO 18N83W MOVING W AT 10 KT.
THE WAVE IS LOCATED NEAR THE BASE OF AN UPPER LEVEL TROUGH OVER
THE WESTERN CARIBBEAN WITH STRONG NORTHERLY WINDS ALOFT
INHIBITING ANY SIGNIFICANT DEEP CONVECTION. HOWEVER...ISOLATED
MODERATE CONVECTION IS FROM 14N-17N BETWEEN 82W-85W. FINALLY...
GIVEN THE HOSTILE ENVIRONMENT ALOFT...THE WAVE IS BECOMING MORE
DIFFICULT TO TRACK AND WILL LIKELY LOSE ITS IDENTITY UPON MOVING
ACROSS THE ROUGH TERRAIN OF CENTRAL AMERICA.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 14N17W TO
09N26W TO 12N37W TO 08N46W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 08N46W TO 08N59W. ASIDE FROM CONVECTION
ASSOCIATED WITH THE SPECIAL FEATURES LOW...WIDELY SCATTERED
MODERATE CONVECTION IS FROM 05N-12N BETWEEN 21W-30W.

...DISCUSSION...

GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED
OVER CENTRAL MEXICO NEAR 20N99W THAT IS PROVIDING THE GULF BASIN
WITH NORTHWEST TO NORTHERLY FLOW ALOFT THIS EVENING. 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 1017 MB HIGH CENTERED ALONG THE FLORIDA PANHANDLE
COAST NEAR 30N86W FURTHER PROMOTES THE FAIR CONDITIONS WITH ONLY
A FEW ISOLATED SHOWERS OCCURRING ACROSS THE NW GULF N OF 26N W OF
92W AS SOUTHEASTERLY RETURN FLOW CONTINUES TO ADVECT LOW-LEVEL
MOISTURE INLAND ACROSS EASTERN TEXAS AND WESTERN LOUISIANA.
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 19N79W AND EXTENDS A TROUGH
AXIS SOUTHWARD ALONG 80W TO A BASE OVER THE SW CARIBBEAN NEAR
10N83W. WEST OF THE TROUGH AXIS...WATER VAPOR IMAGERY INDICATES
VERY DRY AND STABLE AIR WITHIN NORTHERLY FLOW PROVIDING FOR
RELATIVELY QUIET CONDITIONS THIS EVENING N OF 18N W OF 80W.
HOWEVER S OF 18N...A TROPICAL WAVE IS ALONG 84W AND CONTINUES TO
GENERATE SCATTERED SHOWERS AND ISOLATED TSTMS OFF THE HONDURAS
COAST FROM 15N-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 FROM 10N-14N BETWEEN 76W-84W AND
FROM 14N-20N BETWEEN 71W-79W. FINALLY...A WEAK TROPICAL WAVE IS
ANALYZED ALONG 61W IMPACTING THE LESSER ANTILLES THIS EVENING
WITH MUCH OF THE PRECIPITATION ASSOCIATED WITH THE WAVE REMAINING
TO THE EAST OF THE LEEWARD ISLANDS E OF 60W 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 OVER NORTHERN SOUTH AMERICA
NORTHWARD ACROSS THE CENTRAL CARIBBEAN SEA AND SW NORTH ATLC IS
PROVIDING FOR ISOLATED SHOWERS AND TSTMS THROUGH THE OVERNIGHT
PERIOD. 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...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 37N77W THAT SUPPORTS AN OCCLUDED 1010 MB LOW CENTERED
OFFSHORE NEAR 37N74W. A STATIONARY FRONT EXTENDS FROM THE LOW
PRESSURE SYSTEM INTO THE DISCUSSION AREA NEAR 32N70W TO 26N73W
AND BECOMES A SURFACE TROUGH TO EASTERN CUBA NEAR 20N78W. 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 64W-78W...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 1026 MB HIGH CENTERED NEAR 36N42W AND A 1020 MB HIGH
CENTERED NEAR 31N19W. BRIDGING BOTH OF THESE HIGH CENTERS IS A
WEAK STATIONARY FRONT ANALYZED FROM 32N28W TO 29N38W TO 32N49W.
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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