[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST WED DEC 18 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...ITCZ/MONSOON TROUGH...
THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS ALONG 06N15W TO
06N28W TO THE EQUATOR NEAR 45W. ISOLATED MODERATE CONVECTION IS
FROM 03N-09N BETWEEN 11W-34W. A SURFACE TROUGH IS ANALYZED FROM
THE ITCZ AXIS NEAR 07N28W TO THE CAPE VERDE ISLANDS NEAR 15N24W
IN ASSOCIATION WITH A VIGOROUS MIDDLE TO UPPER LEVEL LOW
CENTERED NEAR 18N31W. WITH PLENTY OF MOISTURE ADVECTION
OCCURRING WITHIN THE AREA OF MAXIMUM MIDDLE TO UPPER LEVEL
DIFFLUENCE...SCATTERED MODERATE CONVECTION IS OCCURRING FROM 09N-
21N BETWEEN 15W-27W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES A VERY BROAD MIDDLE TO UPPER LEVEL
LONGWAVE TROUGH MOVING OFFSHORE OF THE NE AND MID-ATLC CONUS
WITH A BASE NOTED OVER PORTIONS OF THE SW NORTH ATLC...FLORIDA
PENINSULA...AND THE NE GULF. ON THE SOUTHWESTERLY PERIPHERY OF
THE TROUGHING...PRIMARILY WEST-NORTHWESTERLY DRY AIR AND STABLE
FLOW ALOFT CONTINUES TO INFLUENCE THE GULF THIS AFTERNOON. AT
THE SURFACE...RIDGING FURTHER SUPPORTS THE STABILITY ALOFT
ANCHORED BY A 1026 MB HIGH CENTERED ACROSS THE NW GULF NEAR
27N95W. NORTHEASTERLY WINDS IN THE RANGE OF 5 TO 15 KT...WITH
THE EXCEPTION OF PORTIONS OF THE EASTERN GULF IN THE RANGE OF 10
TO 20 KT...ARE EXPECTED TO GRADUALLY VEER MORE EASTERLY BY EARLY
THURSDAY. AS THE HIGH PRESSURE AREA IS SHIFTS EASTWARD OVERNIGHT
INTO EARLY THURSDAY...E-SE FLOW WILL RE-ESTABLISH ACROSS THE
NORTHWESTERN HALF OF THE BASIN AS AN AREA LOW PRESSURE BEGINS TO
DEVELOP ACROSS THE CENTRAL HIGH PLAINS OF COLORADO...WESTERN
KANSAS...AND THE TEXAS AND OKLAHOMA PANHANDLES. SOUTHERLY RETURN
FLOW IS EXPECTED TO INCREASE BY THE WEEKEND ACROSS THE WESTERN
GULF AHEAD OF THE NEXT COLD FRONT EXPECTED TO EMERGE OFF THE
TEXAS AND LOUISIANA COASTS EARLY SUNDAY.

CARIBBEAN SEA...
SOUTH-SOUTHWESTERLY FLOW ALOFT CONTINUES OVER THE WESTERN
CARIBBEAN W OF 70W BETWEEN BROAD TROUGHING TO THE NORTH OVER THE
FLORIDA PENINSULA AND AN UPPER LEVEL RIDGE OVER THE CENTRAL
CARIBBEAN WITH AXIS ALONG 70W. WATER VAPOR IMAGERY INDICATES
AMPLE MIDDLE TO UPPER LEVEL MOISTURE ADVECTION IS OCCURRING OVER
CENTRAL AMERICA AND THE WESTERN CARIBBEAN THAT CONTINUES TO
SUPPORT WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS GENERALLY
WEST OF 76W. LOW-LEVEL MOISTURE CONVERGENCE OF THE TRADES...IN
TANDEM WITH THE FAVORABLE MIDDLE TO UPPER LEVEL DYNAMICS IS
GENERATING THIS ACTIVITY WITH THE MOST INTENSE CONVECTION
OCCURRING S OF 12N IN CLOSE PROXIMITY OF THE MONSOON TROUGH
AXIS. FARTHER EAST...UPPER LEVEL WEST-NORTHWESTERLY FLOW E OF
70W REMAINS VERY DRY AND STABLE WITH MOSTLY FAIR SKIES AND
CONDITIONS NOTED FOR HISPANIOLA...PUERTO RICO...AND THE LESSER
ANTILLES. A FEW PASSING ISOLATED SHOWERS ARE HOWEVER POSSIBLE
ACROSS THE EASTERN CARIBBEAN AS THESE SHOWERS REMAIN EMBEDDED
WITHIN TRADE WINDS RANGING FROM 15 TO 25 KT.

...HISPANIOLA...
CURRENTLY RELATIVELY DRY AIR AND STABLE CONDITIONS ALOFT PREVAIL
WITH SATELLITE IMAGERY INDICATING ONLY LOWER LEVEL CLOUDINESS
AND POSSIBLE ISOLATED SHOWERS OCCURRING ACROSS WESTERN PORTIONS
OF THE ISLAND INCLUDING THE ADJACENT COASTAL WATERS BETWEEN 68W-
71W THIS AFTERNOON. THE OVERALL STABILITY WILL LIKELY LIMIT ANY
SIGNIFICANT CONVECTION...HOWEVER AN ISOLATED SHOWER CANNOT BE
RULED OUT DURING THE LATE AFTERNOON AND EARLY EVENING HOURS WITH
PEAK DAYTIME HEATING AND INSTABILITY OCCURRING NEAR THE SURFACE.
LOOKING AHEAD...A MOSTLY NORMAL PATTERN OF WINTER TIME TRADES IS
EXPECTED TO CONTINUE ACROSS THE ISLAND WITH WINDS INCREASING
SLIGHTLY THURSDAY INTO FRIDAY DUE TO A STRENGTHENING PRESSURE
GRADIENT ACROSS THE REGION. THE STRONG TRADES WILL PERSIST
DURING THE UPCOMING WEEKEND.

ATLANTIC OCEAN...
A BROAD MIDDLE TO UPPER LEVEL LONGWAVE TROUGH IS NOTED ON WATER
VAPOR IMAGERY OFF THE NEW ENGLAND AND MID-ATLC COAST THAT
SUPPORTS A STATIONARY FRONT ANALYZED INTO THE DISCUSSION AREA
NEAR 32N63W EXTENDING SW TO THE CENTRAL BAHAMAS NEAR 24N76W THEN
TO CENTRAL CUBA. ISOLATED SHOWERS AND TSTMS ARE OCCURRING WITHIN
150 NM EAST OF THE FRONT. WHILE THE FRONT IS FORECAST TO
GRADUALLY WEAKEN AND BECOME DIFFUSE OVERNIGHT INTO THURSDAY...A
COLD FRONT CURRENTLY ANALYZED FROM 33N72W TO 31N76W WILL BECOME
THE PRIMARY BOUNDARY WEDNESDAY ACROSS THE SW NORTH ATLC. FARTHER
EAST...THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER
THE INFLUENCE OF A LARGE AREAL SURFACE RIDGE ANCHORED BY A 1033
MB HIGH CENTERED NEAR 33N31W.

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

$$
HUFFMAN


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