Prognostic Meteorological Discussion
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FXCA20 KWBC 141842
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 PM EST THU DEC 14 2017

TROPICAL DISCUSSION FROM DEC 14/12 UTC: FAIR CONDITIONS ARE
ESTABLISHING ACROSS MOST OF THE CARIBBEAN/CENTRAL AMERICAN BASIN.
A ROBUST UPPER RIDGE CENTERS OVER MOST OF THE CARIBBEAN...AND HAS
ALSO A REFLECTION INTO THE MID-LEVELS. AS RIDGE PATTERN
STRENGTHENS THROUGH THE FORECAST CYCLE...EXPECTING A STRENGTHENING
OF THE TRADE WIND CAP ACROSS THE CARIBBEAN...WHICH WILL RESULT IN
A GENERAL DECREASING TREND IN ACCUMULATIONS.

IN MEXICO...A LARGE POLAR MID-UPPER TROUGH IS DIGGING FROM THE
NORTH TO EXTEND ACROSS BAJA CALIFORNIA AND SONORA BY THURSDAY
EVENING...ACROSS WEST TEXAS-CHIHUAHUA-SOUTHERN SONORA-BAJA
CALIFORNIA BY FRIDAY EVENING...TO THEN START LIFTING TO THE
NORTHEAST AND EXTEND ACROSS WEST TEXAS-COAHUILA-EASTERN DURANGO BY
SATURDAY EVENING. THE UPPER TROUGH IS INTERACTING WITH A
SUBTROPICAL MOISTURE PLUME/ATMOSPHERIC RIVER THAT ORIGINATES IN
THE TROPICAL PACIFIC. THIS WILL LEAD TO UNUSUALLY HEAVY
PRECIPITATION IN PARTS OF NORTHERN MEXICO...ESPECIALLY DURING
FRIDAY-EARLY SATURDAY...WHEN ENHANCEMENT WILL BE PROVIDED BY THE
DIVERGENT ENTRANCE OF AN UPPER JET. THROUGH EARLY
FRIDAY...EXPECTING LARGEST RAINFALL ACCUMULATIONS IN
SINALOA/NAYARIT WITH AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM.
INLAND INTO ZACATECAS/SAN LUIS POTOSI EXPECTING 05-10MM/DAY AND
MAXIMA OF 15-20MM. IN CHIHUAHUA/COAHUILA EXPECTING 00-05MM/DAY AND
MAXIMA OF 10MM. BY FRIDAY SATURDAY...RAINFALL IS TO PEAK TO
PRODUCE ACCUMULATIONS OF 15-20MM/DAY AND MAXIMA OF 25-50MM FROM
SINALOA/NAYARIT NORTH INTO COAHUILA AND SAN LUIS POTOSI. BY
SATURDAY-SUNDAY EXPECTING A DECREASE IN ACCUMULATIONS...TO
10-15MM/DAY AND MAXIMA OF 20-35MM ACROSS NAYARIT/JALISCO...AND
05-10MM/DAY AND MAXIMA OF 15-20MM IN COAHUILA/SAN LUIS POTOSI.

IN THE MEANTIME...A SURFACE FRONT WILL MAKE IT INTO THE
NORTHWESTERN GULF OF MEXICO ON THURSDAY. BY THURSDAY EVENING IT
WILL EXTEND ACROSS THE RIO BRAVO...WHILE ON FRIDAY EVENING IT WILL
EXTEND INTO SOUTHERN VERACRUZ...TO THEN RETREAT TO THE NORTH. THIS
WILL LEAD TO RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM ON
FRIDAY-SATURDAY.

SURFACE FRONT EXTENDING ACROSS THE GREATER ANTILLES IS STARTING TO
RETREAT AS A WARM FRONT TO THE NORTHWEST...WHILE IT BECOMES
ILL-DEFINED. BY THURSDAY EVENING IT WILL EXTEND ACROSS THE TURKS
AND CAICOS/SOUTHEASTERN BAHAMAS INTO THE CAYMAN ISLANDS...AND BY
FRIDAY EVENING...THE ILL-DEFINED BOUNDARY WILL EXTEND ACROSS THE
CENTRAL BAHAMAS AND CENTRAL CUBA. AS THE FRONT WEAKENS...AND UNDER
THE INFLUENCE OF THE BUILDING MID-LEVEL RIDGE AND ASSOCIATED
SUBSIDENCE CAP...EXPECTING A RAPID DECREASE IN RAINFALL
ACCUMULATIONS. THROUGH EARLY FRIDAY...EXPECTING 05-10MM/DAY AND
MAXIMA OF 15MM IN NORTHERN HISPANIOLA/SOUTHEASTERN CUBA AND THE
SOUTHEASTERN BAHAMAS. LIGHTER AMOUNTS ARE EXPECTED IN JAMAICA AND
THE CAYMAN ISLANDS. ACTIVITY WILL BECOME MORE ISOLATED FROM FRIDAY
AND ON.

IN CENTRAL AMERICA...AS THE FRONT WEAKENS TO THE EAST...EASTERLY
TRADE WINDS ARE TO RETURN DURING THURSDAY. THIS WILL BRING BACK
THE MOISTURE LINGERING OVER OPEN WATERS OF THE SOUTHERN CARIBBEAN.
AS MOISTURE RETURNS...EXPECTING RAINFALL ACCUMULATIONS OF
05-10MM/DAY AND MAXIMA OF 15MM ACROSS COSTA
RICA/NICARAGUA/NORTHERN HONDURAS ON THURSDAY-FRIDAY. DURING
FRIDAY-SATURDAY...EXPECTING 05-10MM/DAY AND MAXIMA OF 15-20MM
SPREADING INTO BELIZE/SOUTHERN GUATEMALA AND THE EASTERN YUCATAN
PENINSULA. SIMILAR AMOUNTS ARE EXPECTED IN EASTERN
HONDURAS/EASTERN NICARAGUA AND COSTA RIGA DURING THIS PERIOD IN
ASSOCIATION WITH AN ARRIVING EASTERLY WAVE (SEE BELOW)

QUIET PATTERN IS ESTABLISHING IN NORTHERN SOUTH AMERICA. ACTIVITY
IS ORGANIZED WITH AN EASTERLY WAVE THAT IS PROPAGATING FROM THE
VENEZUELA COAST ON LATE THURSDAY TO WESTERN CENTRAL AMERICA BY
LATE SATURDAY. THIS WILL LEAD TO A TRANSIENT ENHANCEMENT OF
SHALLOW CONVECTION INITIALLY...AND WILL ALLOW FOR THE DEVELOPMENT
OF A FEW THUNDERSTORMS ONCE IT ARRIVES IN CENTRAL AMERICA ON
FRIDAY. ELSEWHERE IN SOUTH AMERICA...DIURNAL CONVECTION IN WESTERN
COLOMBIA WILL LEAD TO MAXIMA OF 15MM/DAY...WHILE IN THE
GUIANAS...ACTIVE CONVECTION WILL CLUSTER MOSTLY IN FRENCH GUIANA
UNDER THE INFLUENCE OF ITCZ CONVERGENCE.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL  24   36   48   60   72   84   96     TYPE     SOF
72W     76W  80W  84W  88W   93W  97W  101W    EW       15N

AN EASTERLY WAVE IS INITIALIZED AT 72W. THIS WAVE WILL ENHANCE
SHALLOW CONVECTION IN THE ABC AND NORTHWESTERN VENEZUELA ON
THURSDAY. ON FRIDAY-SATURDAY IT WILL STIMULATE CONVECTION IN THE
FAR SOUTHWESTERN CARIBBEAN AND ALONG THE COASTS OF NICARAGUA AND
HONDURAS...WHERE IT WILL LEAD TO ACCUMULATIONS OF 05-10MM/DAY AND
ISOLATED MAXIMA OF 15-25MM. BY SATURDAY-SUNDAY THE WAVE WILL
STIMULATE CONVECTION LONG NORTHERN HONDURAS AND SOUTHERN
BELIZE/SOUTHERN GUATEMALA...WHERE EXPECTING SIMILAR RAINFALL
AMOUNTS. IN THE NORTHERN YUCATAN PENINSULA EXPECTING 05-10MM/DAY
AND MAXIMA OF 15-20MM.

GORDON...NMS (BELIZE)
PECK...MS (JAMAICA)
RIVAS...SENAMHI (PERU)
GALVEZ/DAVISON...WPC (USA)

$$





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