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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1854Z Dec 16, 2014)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
154 PM EST TUE DEC 16 2014

DISCUSSION FROM DECEMBER 16/00UTC: CONSISTENT WITH PREVIOUS
FORECAST...A MID/UPPER LEVEL RIDGE IS TO GRADUALLY BUILD ACROSS
THE CARIBBEAN BASIN. AT 500 HPA THE RIDGE IS TO ORIGINATE ON A
CLOSED HIGH OVER CHIAPAS IN SOUTHERN MEXICO/GUATEMALA. EARLY IN
THE CYCLE THE RIDGE IS TO CONFINE TO CENTRAL AMERICA/WESTERN
CARIBBEAN. THROUGH WEDNESDAY EVENING/EARLY THURSDAY MORNING THE
RIDGE BUILDS ACROSS THE GREATER ANTILLES/NORTHERN CARIBBEAN
ISLES...AND LATER ON THURSDAY IT BUILDS SOUTH INTO NORTHERN SOUTH
AMERICA. AS THE RIDGE EXPANDS ACROSS THE BASIN...IT IS TO
STRENGTHEN THE TRADE WINDS CAP WHILE SUSTAINING A DRYING TREND.
THIS IS MOST NOTICEABLE OVER THE NORTHERN CARIBBEAN ISLES...WHERE
PWAT DROPS FROM 40-45MM EARLY IN THE CYCLE TO 25-30MM LATER ON
THURSDAY.

POLAR PERTURBATIONS ON THE SOUTHERN STREAM ARE TO LIFT OVER THIS
RIDGE AS IT MEANDERS OVER SOUTHERN MEXICO/THE GULF. TWO
PERTURBATIONS ARE OF INTEREST... WITH ONE ENTERING NORTHWEST
MEXICO LATER THIS EVENING AND ANOTHER THAT MAKES LANDFALL LATER ON
THURSDAY. IN INTERACTION WITH THE RIDGE TO THE SOUTH THESE ARE TO
FAVOR A MOIST ADVECTIVE PATTERN INTO NORTHERN PORTIONS OF BAJA
PENINSULA-SONORA IN NORTHWEST MEXICO. IN THIS AREA EXPECTING
SCATTERED CONVECTION TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 15MM LATER TODAY...WHILE ON WEDNESDAY TO THURSDAY
EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM.

PROGRESSIVE MID/UPPER LEVEL TROUGH IS PULLING ACROSS THE
TURKS/SOUTHEAST BAHAMAS TO NORTHERN HISPANIOLA. LATER TODAY IT
WILL MOVE ACROSS PUERTO RICO/NORTHEAST CARIBBEAN ISLES. AT 250 HPA
A JET MAXIMA IS TO ACCOMPANY THIS PERTURBATION...WITH DIVERGENCE
ON ITS RIGHT ENTRANCE REGION TO VENT DEEP CONVECTION FROM NORTHERN
HISPANIOLA TO THE NORTHERN LEEWARD/VIRGIN ISLES. AT LOW
LEVELS...AS THE TROUGH ALOFT STREAMS ACROSS THE NORTHERN
CARIBBEAN...IT IS TO INTERACT WITH A MEANDERING FRONT NORTH OF
PUERTO RICO-HISPANIOLA. THIS IS TO TRIGGER ORGANIZED CONVECTION
WITH ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF 30-60MM ACROSS
NORTHERN HISPANIOLA...WHILE OVER PUERTO RICO-USVI/NORTHERN LEEWARD
EXPECTING MAXIMA OF 35-70MM. FRONTAL BOUNDARY IS TO THEN
FRONTOLIZE THROUGH WEDNESDAY MORNING AS THE MID/UPPER TROUGH PULLS
AWAY AND MID LEVEL RIDGE BUILDS ACROSS THE BASIN.

MEANWHILE...AS THE SURFACE FRONT MEANDERS TO THE NORTH...A
PREFRONTAL SHEAR LINE IS TO LIE ACROSS THE NORTHEAST CARIBBEAN TO
A LOW NORTH OF COSTA RICA. BUT AS THE FRONT TO THE NORTH
WEAKENS...AND THE EASTERLY TRADES WANE...THIS IS TO GRADUALLY
BECOME ILL ORGANIZED. MEANWHILE...THIS IS TO ENHANCE MOISTURE
CONVERGENCE ACROSS JAMAICA TO SUSTAIN RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 25-50MM. THROUGH WEDNESDAY EVENING THIS
DECREASES TO 05-10MM/DAY AND MAXIMA OF 15MM...WITH LESSER AMOUNTS
ON THURSDAY. ACROSS SAN ANDRES/ISLA DE LA PROVIDENCIA TO COSTA
RICA/WESTERN PANAMA THIS IS TO SUSTAIN SCATTERED CONVECTION WITH
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-35MM. THROUGH
THURSDAY MORNIGN THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF
15-20MM. FURTHERMORE...AS THE SHEAR LINE WEAKENS...REMAINING
MOISTURE IS TO THEN SPREAD WEST INTO NORTHEAST HONDURAS/EASTERN
NICARAGUA...WHERE IT IS TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 15MM.

OVER THE EASTERN PACIFIC...THE PANAMANIAN LOW IS TO REMAIN ILL
ORGANIZED DURING THE NEXT FEW DAYS...WITH WEAK/OPEN TROUGH TO LIE
ALONG THE WEST COAST OF COLOMBIA. THE ITCZ...MEANWHILE...IS TO
TRAIL ACROSS THE AZUERO PENINSULA IN PANAMA TO NORTHERN
COLOMBIA...WHERE IT IS TO REMAIN OVER THE NEXT FEW DAYS. THE ILL
ORGANIZED PANAMANIAN LOW WILL NOT BE CONDUCIVE TO A MOIST
ADVECTIVE PATTERN ACROSS COLOMBIA. AS A RESULT...ON THE WESTERN
PLAINS-ANDEAN REGION-NORTHERN COLOMBIA ONLY EXPECTING RAINFALL
AMOUNTS OF 05-10MM/DAY AND ISOLATED MAXIMA OF 15-20MM THROUGH
FRIDAY MORNING. OVER THE ATLANTIC...THE ITCZ IT TO MEANDER WEST
ACROSS THE NORTHERN GUIANAS ALONG 05N TO CENTRAL VENEZUELA. ACROSS
FRENCH GUIANA TO SURINAME THIS IS TO FAVOR RAINFALL AMOUNTS OF
00-05MM/DAY AND WIDELY ISOLATED MAXIMA OF 10MM. SIMILAR AMOUNTS
ARE EXPECTED ACROSS NORTHERN GUYANA TO NORTHEAST VENEZUELA/THE
GRENADINES IN LIGHT TRADE WIND SHOWERS.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96     TYPE

NONE.

JN BAPTISTE...MS (SAINT LUCIA)
NANDA...MDS (SURINAME)
DAVISON...WPC (USA)