Prognostic Meteorological Discussion
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 PM EST WED JAN 17 2018

TROPICAL DISCUSSION FROM JAN 17/12 UTC: AT UPPER LEVELS...THE
SUBEQUATORIAL RIDGE EXTENDS FROM NORTHERN SOUTH AMERICA INTO THE
CENTRAL AND EASTERN CARIBBEAN. THE NORTHERN FRINGES OF THIS RIDGE
EXTEND INTO JAMAICA...SOUTHEASTERN CUBA...THE TURKS AND CAICOS AND
THE SOUTHEASTERN BAHAMAS. AT MID-LEVELS...A RIDGE CENTERS ON A
HIGH JUST TO THE NORTH OF THE MONA PASSAGE/PUERTO RICO...AND
EXTENDS AN AXIS TO THE WEST SOUTHWEST INTO JAMAICA-EASTERN GULF OF
HONDURAS. THESE MID AND UPPER RIDGES ARE LIMITING THE INCURSION OF
POLAR TROUGHS INTO THE CARIBBEAN BASIN. AS GLOBAL MODELS AGREE ON
THE RIDGES GENERALLY HOLDING THROUGH THE CYCLE...RAIN-PRODUCING
PERTURBATIONS ARE TO LIMIT TO AREAS TO THE WEST AND NORTH OF THE
UPPER RIDGES...AND ALONG ITS PERIPHERY. THIS INCLUDES EASTERN
CENTRAL AMERICA...THE GULF OF HONDURAS...JAMAICA...CAYMAN
ISLANDS...CUBA AND THE BAHAMAS.

TO THE NORTH OF THE RIDGE...IN THE WESTERLIES...A STRONG UPPER
TROUGH IS CROSSING THE MISSISSIPPI VALLEY INTO THE EASTERN UNITED
STATES. THIS TROUGH IS SUSTAINING A PROGRESSIVE SURFACE COLD FRONT
THAT IS PROPAGATING ACROSS THE GULF OF MEXICO. BY WEDNESDAY
EVENING...THE POLAR FRONT IS FORECAST TO EXTEND ACROSS SOUTHERN
FLORIDA...THE SOUTHEASTERN GULF...INTO THE EXTREME NORTHERN
YUCATAN PENINSULA. SIMULTANEOUSLY...AN ILL DEFINED OLD FRONT WILL
EXTEND TO ITS SOUTH ACROSS THE CENTRAL BAHAMAS......CENTRAL
CUBA...AND INTO CAYMAN ISLANDS...WHERE THE BOUNDARY WILL BE
ILL-DEFINED. THE LATTER WILL ALSO SUSTAIN A SHEAR LINE THAT...BY
WEDNESDAY EVENING IS FORECAST TO EXTEND ACROSS SOUTHEASTERN
CUBA...WESTERN JAMAICA...SAN ANDRES/NUEVA PROVIDENCIA...COSTA
RICA. THE FRONTS ARE TO MERGE DURING THURSDAY...AND BY THURSDAY
EVENING THE BOUNDARY WILL EXTEND ACROSS THE SOUTHEASTERN
BAHAMAS/TURKS AND CAICOS...SOUTHEASTERN CUBA...CAYMAN ISLANDS AND
NORTHERN HONDURAS/SOUTHERN BELIZE. ALSO BY THURSDAY EVENING...THE
SHEAR LINE WILL EXTEND ACROSS NORTHERN HAITI...INTO SOUTHERN
NICARAGUA. BY FRIDAY EVENING THE FRONT WILL EXTEND ACROSS THE
SOUTHEASTERN BAHAMAS...CENTRAL CUBA...INTO THE GULF OF HONDURAS.
THE SHEAR LINE WILL START LOSING DEFINITION TO EXTEND ACROSS
EASTERN HISPANIOLA...INTO THE HAITIAN PENINSULA...JUST TO THE
SOUTH OF JAMAICA. BY SATURDAY...THE FRONT WILL RETROGRESS
NORTHWARD TO EXTEND ACROSS THE CENTRAL BAHAMAS AND CUBA WHILE
LOSING DEFINITION.

IN TERMS OF ACCUMULATIONS...LARGEST AMOUNTS ARE EXPECTED IN THE
GULF OF HONDURAS REGION/COSTA RICA AND PANAMA...WHERE MOISTURE
CONVERGENCE WILL PEAK AS THE FRONT AND SHEAR LINE INTERACT WITH
OROGRAPHY. FURTHERMORE...UPPER VENTILATION IN THE RIGHT DIVERGENT
ENTRANCE OF AN UPPER JET TO THE NORTH WILL BE FAVORABLE FOR THE
CONTINUED DEVELOPMENT OF HEAVY-RAIN PRODUCING THUNDERSTORMS DURING
WEDNESDAY-THURSDAY IN AREAS OF THE GULF OF HONDURAS. IN TERMS OF
RAINFALL AMOUNTS...THROUGH EARLY THURSDAY...EXPECTING 25-50MM/DAY
AND MAXIMA OF 75-150MM IN NORTHERN HONDURAS. IN NORTHERN COSTA
RICA/SOUTHEASTERN NICARAGUA EXPECTING 15-30MM/DAY AND MAXIMA OF
40-80MM. IN EASTERN COSTA RICA/WESTERN PANAMA EXPECTING
15-20MM/DAY AND MAXIMA OF 25-50MM WITH THE SHEAR LINE. IN THE
NORTHERN BAHAMAS EXPECTING 10-15MM/DAY AND MAXIMA OF 20-35MM WHERE
THUNDERSTORMS DEVELOP. IN CENTRAL CUBA...CAYMAN ISLANDS... AND
SOUTHERN BELIZE EXPECTING 05-10MM/DAY AND ISOLATED MAXIMA OF
15-25MM. IN JAMAICA...EXPECTING MAXIMA OF 15MM. BY THURSDAY-EARLY
FRIDAY EXPECTING LARGEST AMOUNTS IN NORTHERN HONDURAS AND EXTREME
SOUTHERN BELIZE/EASTERN GUATEMALA WHERE ENHANCED MOISTURE
CONVERGENCE WILL LEAD TO 25-50MM/DAY AND MAXIMA OF 75-150MM.
ENHANCED MOISTURE CONVERGENCE IN WESTERN PANAMA/EASTERN COSTA RICA
WILL LEAD TO 15-20MM/DAY AND MAXIMA OF 40-80MM. FRONTAL AND
SHEAR-LINE CONVECTION IN SOUTHEASTERN CUBA/NORTHEASTERN HISPANIOLA
AND THE TURKS AND CAICOS AND NORTHERN JAMAICA WILL LEAD TO
05-10MM/DAY AND MAXIMA OF 15-25MM...UNDER INTERACTION WITH
OROGRAPHY. BY FRIDAY-SATURDAY...EXPECTING LARGEST ACCUMULATIONS ON
EASTERN HISPANIOLA...WHERE SHEAR-LINE CONVECTION WILL LEAD TO
15-20MM/DAY AND MAXIMA OF 25-50MM. IN CENTRAL AMERICA...SHEAR LINE
CONVECTION WILL LEAD TO 10-15MM/DAY AND MAXIMA OF 20-45MM. ALSO IN
CENTRAL AMERICA...AS MOISTURE CONVERGENCE PEAKS TO THE SOUTH OF
THE CARIBBEAN LOW-LEVEL JET...EXPECTING LOCALLY HEAVY RAINFALL IN
EASTERN COSTA RICA/WESTERN PANAMA WITH ACCUMULATIONS OF
30-60MM/DAY AND MAXIMA OF 100-150MM. IN NORTHERN COSTA
RICA/SOUTHEASTERN NICARAGUA EXPECTING 15-20MM/DAY AND MAXIMA OF
30-60MM.

IN THE NORTHEASTERN CARIBBEAN...MID-LEVEL RIDGE PATTERN IS TO
PERSIST. A SUBSIDENCE CAP IS WELL DEFINED IN THE
MID-TROPOSPHERE...YET IT IS SUFFICIENTLY ELEVATED TO ALLOW SOME
VERTICAL DEVELOPMENT AND MODERATE AFTERNOON SHOWERS IN WESTERN
PUERTO RICO AND HISPANIOLA. THIS WILL LEAD TO 15-20MM/DAY AND
MAXIMA OF 25-50MM ON WEDNESDAY AND FRIDAY...AND LESSER AMOUNTS ON
THURSDAY. ELSEWHERE ACCUMULATIONS WILL BE GENERALLY UNDER 10MM.

IN NORTHERN SOUTH AMERICA...LARGEST ACCUMULATIONS ARE TO CLUSTER
IN THE AMAZON BASIN INCLUDING SOUTHEASTERN COLOMBIA. EXPECTING
15-20MM/DAY AND MAXIMA OF 25-50MM ON A DAILY BASIS. ISOLATED
LARGER AMOUNTS ARE EXPECTED IN STRONGEST THUNDERSTORMS.
ELSEWHERE...MODERATE RAINFALL AMOUNTS ARE EXPECTED WHERE THE
ATLANTIC ITCZ CONVERGES WITH THE COAST. THIS WILL LEAD TO TOTALS
OF 10-15MM/DAY AND MAXIMA OF 20-35MM IN THE GUIANAS ON
WEDNESDAY...DECREASING IN COVERAGE AND INTENSITY AS THE CYCLE
PROGRESSES...TO PRODUCE 05-10MM/DAY AND MAXIMA OF 15-20MM BY
FRIDAY. IN COLOMBIA...DIURNAL CONVECTION WILL LEAD TO 05-10MM/DAY
AND ISOLATED MAXIMA OF 15-20MM...WHILE IN SOUTHWESTERN
COLOMBIA/CAUCA VALLEY AND NORTHWESTERN ECUADOR EXPECTING
10-15MM/DAY AND MAXIMA OF 20-35MM THROUGH THURSDAY MORNING.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL  24  36   48   60   72   84   96           TYPE   SOF
NONE

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

$$





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