Prognostic Meteorological Discussion
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 PM EST TUE JAN 16 2018

TROPICAL DISCUSSION FROM JAN 16/12 UTC: UPPER RIDGE EXTENDS FROM
NORTHEASTERN SOUTH AMERICA ACROSS VENEZUELA INTO
JAMAICA-HISPANIOLA AND PUERTO RICO. THIS PATTERN IS FORECAST TO
HOLD THROUGH THE CYCLE. AT MID-LEVELS...A RIDGE IS FORECAST TO
MEANDER ALONG THE NORTHERN CARIBBEAN ISLES INTO THE GULF OF
HONDURAS THROUGH THE CYCLE. AS THIS RIDGE CONFIGURATION HOLDS...IT
WILL FORCE UPPER TROUGHS TO MEANDER EAST-NORTHEASTWARD ALONG THE
GULF OF MEXICO/UNITED STATES...WITHOUT DIGGING INTO THE NORTHERN
CARIBBEAN. AS A RESULT...ASSOCIATED SURFACE FRONTS AND SHEAR LINES
WILL LIMIT TO CENTRAL AMERICA AND THE EXTREME NORTHWESTERN
CARIBBEAN/CUBA/BAHAMAS.

INITIALLY...A LINGERING SURFACE FRONT WILL CONTINUE MEANDERING
NORTHWESTWARD ACROSS THE NORTHWESTERN ANTILLES-NORTHERN HONDURAS.
BY TUESDAY EVENING IT WILL EXTEND ACROSS ANDROS ISLAND IN THE
NORTH-CENTRAL BAHAMAS...NORTH-CENTRAL CUBA...INTO THE NORTHERN
YUCATAN PENINSULA. THIS WILL BE ACCOMPANIED BY AN ILL-DEFINED
SHEAR-LINE THAT WILL EXTEND ACROSS CENTRAL CUBA...CAYMAN
ISLANDS...NORTHEASTERN HONDURAS. AS A POLAR HIGH BUILDS OVER THE
CENTRAL USA...NORTHERLY WINDS ARE TO INCREASE DURING LATE TUESDAY
INTO WEDNESDAY ACROSS THE NORTHWESTERN CARIBBEAN. THIS WILL PUSH
THE FRONT ONCE AGAIN TO THE SOUTHEAST WHILE IT WEAKENS. BY
WEDNESDAY EVENING THE ILL-DEFINED FRONT WILL EXTEND ACROSS
CENTRAL-EASTERN CUBA...NORTHWEST OF THE CAYMAN ISLANDS...INTO
QUINTANA ROO...TO LOSE DEFINITION AFTER. BY THIS TIME...THE SHEAR
LINE WILL EXTEND ACROSS EASTERN CUBA...BETWEEN THE JAMAICA...AND
INTO SAN ANDRES ISLAND AND COSTA RICA.

A SECOND FRONT WILL ENTER THE BASIN ON TUESDAY. BY TUESDAY EVENING
IT WILL EXTEND ACROSS THE NORTHWESTERN GULF INTO A LOW AT 24N
95W...TO CENTRAL VERACRUZ. BY WEDNESDAY EVENING THE FRONT WILL
EXTEND ACROSS THE NORTHERN BAHAMAS...NORTHERN CUBA...NORTHERN
YUCATAN INTO SOUTHERN VERACRUZ. BY THURSDAY EVENING THE FRONT WILL
BECOME STATIONARY ACROSS THE SOUTHEASTERN BAHAMAS...SOUTHEASTERN
CUBA...JUST TO THE SOUTH OF THE CAYMAN ISLANDS...INTO NORTHERN
HONDURAS/SOUTHERN BELIZE. THIS NEW FRONT WILL INTERACT WITH THE
SHEAR LINE...WHICH IS FORECAST TO EXTEND ACROSS NORTHERN
HAITI...INTO SOUTHERN NICARAGUA.

UNDER A PERSISTENT UPPER TROUGH PATTERN TO THE WEST...MODELS
CONTINUE SHOWING FAVORABLE VENTILATION FOR ANY CELL THAT IS FORCED
TO BREAK THE SUBSIDENCE CAP IN EASTERN CENTRAL AMERICA.
ALSO...PRECIPITABLE WATER VALUES REMAIN HIGH ALONG THE EASTERN
COAST OF CENTRAL AMERICA...WITH VALUES EXCEEDING 50MM OFF THE
COASTS OF NICARAGUA AND HONDURAS. THIS WILL SUSTAIN ENHANCED
PRECIPITATION THROUGH THE CYCLE IN THE CARIBBEAN COASTS OF CENTRAL
AMERICA BETWEEN WESTERN PANAMA AND SOUTHERN BELIZE DURING
DIFFERENT PERIODS OF THE CYCLE. THROUGH EARLY WEDNESDAY...LARGEST
ACCUMULATIONS ARE EXPECTED IN NORTHERN AND NORTHEASTERN
HONDURAS...WHERE ENHANCED MOISTURE CONVERGENCE IN THE TAIL OF THE
SHEAR LINE WILL LEAD TO 15-30MM/DAY AND MAXIMA OF 40-80MM. IN
NORTHERN COSTA RICA/SOUTHERN NICARAGUA EXPECTING 15-20MM/DAY AND
MAXIMA OF 25-50MM. WITH THE SURFACE FRONT...EXPECTING
ACCUMULATIONS OF 10-15MM/DAY AND MAXIMA OF 20-30MM IN THE
NORTH-CENTRAL BAHAMAS. IN THE CENTRAL BAHAMAS AND CENTRAL CUBA
EXPECTING 05-10MM/DAY AND MAXIMA OF 15-20MM. SIMILAR AMOUNTS ARE
EXPECTED IN THE CAYMAN ISLANDS UNDER INTERACTION WITH THE SHEAR
LINE...WHEREAS IN JAMAICA...EXPECTING SIMILAR ACCUMULATIONS DUE TO
THE PRE-FRONTAL TROUGH AND INTERACTIONS BETWEEN THE TRADES AND THE
WINDWARD PASSAGE/HISPANIOLA IN REGIONS UPSTREAM. BY WEDNESDAY INTO
EARLY THURSDAY...AS THE NORTHERLY COMPONENT OF THE TRADES
INCREASES IN THE GULF OF HONDURAS...EXPECTING AN INCREASE IN
ACCUMULATIONS TO 15-30MM/DAY AND MAXIMA OF 50-100MM. IN EASTERN
COSTA RICA EXPECTING 15-20MM/DAY AND MAXIMA OF 25-50MM WITH THE
SHEAR LINE. REGARDING THE FRONT...LARGEST ACCUMULATIONS ARE
EXPECTED IN THE NORTHERN BAHAMAS WHERE LOW-LEVEL MOISTURE
CONVERGENCE AND ENHANCED UPPER DIVERGENCE IN THE RIGHT ENTRANCE OF
AN UPPER JET WILL FAVOR RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA
OF 25-50MM. IN CENTRAL CUBA...CAYMAN ISLANDS AND SOUTHERN BELIZE
EXPECTING 05-10MM/DAY AND MAXIMA OF 15-25MM. IN JAMAICA...UNDER
THE INFLUENCE OF THE SHEAR LINE...EXPECTING ISOLATED AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM. 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 75-125MM.
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 WILL LEAD TO 05-10MM/DAY AND MAXIMA OF
15-25MM.

IN THE NORTHEASTERN CARIBBEAN...ALTHOUGH MID-LEVEL RIDGE PATTERN
IS TO PERSIST...TRADE WINDS WILL BE SUFFICIENTLY LIGHT TO FAVOR
CIRCULATIONS TRIGGERED BY DIURNAL HEATING. FURTHERMORE...SST
ANOMALIES ARE ABOVE AVERAGE ACROSS MOST OF THE REGION. THIS IS
SUFFICIENT TO ALLOW FOR AFTERNOON SHOWERS AND ISOLATED
THUNDERSTORMS IN WESTERN PUERTO RICO AND PARTS OF
HISPANIOLA...THAT ARE CAPABLE OF PRODUCING 15-20MM/DAY AND MAXIMA
OF 25-50MM. THIS IS TO CONTINUE THROUGH THURSDAY
MORNING...FOLLOWED BY A DECREASE ON THURSDAY TO 05-10MM/DAY AND
MAXIMA OF 15-25MM.

IN NORTHERN SOUTH AMERICA...LARGEST ACCUMULATIONS ARE TO CLUSTER
IN THE AMAZON BASIN INCLUDING SOUTHEASTERN COLOMBIA. EXPECTING
15-30MM/DAY AND MAXIMA OF 40-80MM THROUGH EARLY
WEDNESDAY...DECREASING TO 15-20MM/DAY AND MAXIMA OF 25-50MM AFTER.
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
TUESDAY-EARLY WEDNESDAY...CONSTRAINING TO FRENCH GUIANA AND AMAPA
IN BRAZIL AFTER. 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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