Prognostic Meteorological Discussion
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FXCA20 KWBC 171819
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
218 PM EDT TUE OCT 17 2017

TROPICAL DISCUSSION FROM OCT 17/12 UTC: STRONG POLAR TROUGH
EXITING THE EAST COAST OF THE UNITED STATES IS SUSTAINING A
SURFACE FRONT AND A SHEAR LINE THAT WILL CONTINUE ENHANCING
ACTIVITY IN NORTHERN CENTRAL AMERICA/SOUTHERN MEXICO. ON
TUESDAY...THE FRONT IS FORECAST TO BECOME STATIONARY NORTH OF THE
BAHAMAS AND EXTEND ACROSS FLORIDA INTO THE NORTHERN/CENTRAL GULF
OF MEXICO. AN ILL-DEFINED  SHEAR LINE IS FORECAST TO EXTEND OVER
THE NORTHERN BAHAMAS/WESTERN CUBA AND THE YUCATAN PENINSULA AREA.
AT THIS TIME...THE POLAR TROUGH AT THE UPPER LEVELS WILL BE AT A
POSITION FAVORABLE FOR ENHANCED CONVECTION OVER THE EASTERN GULF
OF MEXICO...IN A REGION WITH HIGH PRECIPITABLE WATER CONTENT WHERE
VALUES EXCEED 55MM. IN ASSOCIATION WITH THE SYSTEM...A NORTHERLY
WIND SURGE IN THE SOUTHERN GULF OF MEXICO WILL CONTINUE TO SUPPORT
MODERATE PRECIPITATION AMOUNTS OVER SOUTHERN MEXICO AIDED BY
OROGRAPHIC UPLIFT. THIS WILL LEAD TO LOCALIZED AMOUNTS OF
15-30MM/DAY AND MAXIMA OF 35-70MM IN SOUTHERN VERACRUZ ON
TUESDAY-WEDNESDAY. IN THE YUCATAN PENINSULA...SHEAR LINE
CONVECTION WILL LEAD TO AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-30MM. BY WEDNESDAY-THURSDAY...OROGRAPHIC ENHANCEMENT WILL LEAD
TO 15-20MM/DAY AND MAXIMA OF 25-50MM. ALTHOUGH THE SHEAR LINE WILL
LOSE DEFINITION BY THEN...AN ARRIVING TROPICAL WAVE WILL SUSTAIN
SUFFICIENT MOISTURE CONVERGENCE TO PRODUCE 10-15MM/DAY AND MAXIMA
OF 20-30MM/DAY IN THE EASTERN YUCATAN PENINSULA/NORTHERN
BELIZE...AND IN WESTERN CUBA AND THE NORTHERN BAHAMAS. BY
THURSDAY-FRIDAY...THE FRONT WILL ENHANCE PRECIPITATION IN THE
NORTHERN BAHAMAS...WHERE IT WILL LEAD TO 10-15MM/DAY AND ISOLATED
MAXIMA OF 20-35MM. SIMILAR AMOUNTS ARE EXPECTED IN THE
CENTRAL/SOUTHEASTERN BAHAMAS. IN NORTHERN CENTRAL AMERICA...WHILE
TRADES REMAIN FROM THE NORTHEAST...EXPECTING CONTINUED OROGRAPHIC
UPLIFT TO SUSTAIN AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM
FROM SOUTHERN VERACRUZ/CHIAPAS/TABASCO...INTO CENTRAL GUATEMALA
AND SOUTHERN BELIZE. IN THE YUCATAN PENINSULA AND CUBA EXPECTING
ISOLATED AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM.

IN THE CARIBBEAN...A REGION OF INTEREST IS THE EASTERN TIER AND
THE NORTHERN ANTILLES. CURRENTLY...THE WET PATTERN IN THE EASTERN
CARIBBEAN ASSOCIATES WITH AN ITCZ DISPLACED TO THE NORTH OF ITS
CLIMATOLOGICAL POSITION...AND ONE TROPICAL WAVE APPROACHING.
YET...NOTE THAT UNDER THE INFLUENCE OF AN APPROACHING TRADE WIND
SURGE...THE CURRENT WET PATTERN WILL EVOLVE INTO A MUCH DRIER ONE
DURING WEDNESDAY THROUGH FRIDAY. AS THE TRADE WIND SURGE ENTERS
THE BASIN...IT WILL LIMIT LARGEST ACCUMULATIONS TO THE WINDWARD
ISLANDS...WHERE AN ACTIVE ATLANTIC ITCZ IS FORECAST TO MEANDER
DURING THE NEXT SEVERAL DAYS. IN THE MEAN TIME...HOWEVER...THE
TROPICAL WAVE (SEE BELOW) AND ENHANCED LOW-LEVEL CONVERGENCE AHEAD
OF THE TRADE WIND SURGE WILL SUSTAIN MODERATE PRECIPITATION
AMOUNTS. THROUGH EARLY WEDNESDAY...LARGEST AMOUNTS ARE EXPECTED IN
THE LESSER ANTILLES...AS TRAILING PLUME BEHIND THE TROPICAL WAVE
AND CONVERGENCE AHEAD OF THE TRADE WIND SURGE INTERACT. THIS WILL
LEAD TO 15-20MM/DAY AND MAXIMA OF 30-60MM. IN
HISPANIOLA...PRE-FRONTAL TROUGH IN INTERACTION WITH THE MOISTURE
PLUME WILL SUSTAIN 15-20MM/DAY AND MAXIMA OF 25-50MM. IN PUERTO
RICO/VI EXPECTING MAXIMA OF 20-35MM. IN JAMAICA...EXPECTING
ISOLATED AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. BY
WEDNESDAY-THURSDAY...EXPECTING LARGEST ACCUMULATIONS IN THE
SOUTHERN DOMINICAN REPUBLIC...WHERE THE TROPICAL WAVE/MOIST PLUME
WILL FAVOR 15-30MM/DAY AND ISOLATED MAXIMA OF 40-80MM. THE TRADE
WIND SURGE WILL LEAD TO FAIR CONDITIONS IN THE NORTHEASTERN
ANTILLES...YET...ITCZ MOISTURE CONVERGENCE IN THE WINDWARD
ISLANDS/NORTH EASTERN VENEZUELA WILL LEAD TO 15-30MM/DAY AND
MAXIMA OF 35-70MM. BY THURSDAY-FRIDAY...LARGEST AMOUNTS WILL
CLUSTER ONCE AGAIN IN THE SOUTHERN WINDWARDS AND NORTHEASTERN
VENEZUELA/NORTHERN GUYANA...WHERE EXPECTING 15-20MM/DAY AND MAXIMA
OF 25-50MM.

IN NORTHWESTERN SOUTH AMERICA AND SOUTHERN CENTRAL
AMERICA...ACCUMULATIONS WILL BE MODULATED BY A TRAVERSING TROPICAL
WAVE AND ITS INTERACTIONS WITH THE PANAMANIAN LOW. AS THE WAVE
CROSSES PANAMA ON TUESDAY...IT WILL CONTINUE ENHANCING CONVECTION
TO PRODUCE AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM IN PANAMA
AND WESTERN COLOMBIA. ISOLATED HIGHER AMOUNTS ARE EXPECTED IN
EASTERN NICARAGUA AND COSTA RICA...WHERE EXPECTING 15-20MM/DAY AND
MAXIMA OF 30-60MM. BY WEDNESDAY-THURSDAY...EXPECTING 10-15MM/DAY
AND MAXIMA OF 20-40MM IN EASTERN NICARAGUA/EASTERN HONDURAS.
ELSEWHERE IN SOUTHERN CENTRAL AMERICA EXPECTING MAXIMA OF 15-25MM.
BY THURSDAY-FRIDAY...LARGEST AMOUNTS ARE EXPECTED IN EASTERN
NICARAGUA AND COSTA RICA...WHERE EXPECTING 10-15MM/DAY AND MAXIMA
OF 20-35MM. IN COLOMBIA...ITCZ/NET CONVERGENCE AND WESTERLIES
ALONG THE PACIFIC BASIN WILL SUSTAIN AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-35MM ON A DAILY BASIS.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24    36    48    60    72    84    96   TYPE  SOF
62W      64W   67W   69W   72W   74W   76W   78W   TW    17N
81W      83W   85W   87W   90W   92W   93W   94W   TW    18N

TROPICAL WAVE INITIALIZED AT 62W WILL CONTINUE STIMULATING
CONVECTION AS IT PROPAGATES WEST ACROSS THE CARIBBEAN BASIN. THE
WAVE WILL STIMULATE CONVECTION IN PUERTO RICO/VI AND CENTRAL
VENEZUELA ON TUESDAY...HISPANIOLA AND WESTERN VENEZUELA ON
WEDNESDAY...AND NORTHERN COLOMBIA AND JAMAICA ON THURSDAY. NOTE
THAT MODELS ARE SUGGESTING MODERATE RAINFALL AMOUNTS IN JAMAICA
DURING FRIDAY...AS TROPICAL WAVE AND MOIST PLUME INTERACT WITH THE
ISLAND. IN THE MEAN TIME...EXPECTING ISOLATED AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM ON THURSDAY.

A TROPICAL WAVE INITIALIZED AT 81W IS ORGANIZING AS IT APPROACHES
SOUTHERN CENTRAL AMERICA. THE WAVE IS FORECAST TO ENTER COSTA
RICA/NICARAGUA LATE ON TUESDAY/EARLY WEDNESDAY. BY
WEDNESDAY-THURSDAY...IT WILL ENHANCE CONVECTION IN
HONDURAS/EASTERN YUCATAN...AND BY THURSDAY-FRIDAY...IT WILL
ENHANCE ACTIVITY SLIGHTLY ACROSS GUATEMALA/CHIAPAS.

GUY...NMS (BELIZE)
PECK...MS (JAMAICA)
GALVEZ...WPC (USA)
$$





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