Prognostic Meteorological Discussion
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FXCA20 KWBC 181904
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
204 PM EST THU DEC 18 2014

DISCUSSION FROM DECEMBER 18/00UTC: AT 500 HPA...A CLOSED HIGH OVER
SOUTHERN MEXICO IS TO EXTEND A RIDGE ACROSS THE CARIBBEAN BASIN TO
NORTHERN SOUTH AMERICA LATER THIS EVENING. ALTHOUGH RIDGE TENDS TO
WEAKEN OVER MEXICO AS A TROUGH AMPLIFIES TO THE NORTH...AXIS OVER
THE CARIBBEAN-CENTRAL AMERICA AND NORTHERN SOUTH AMERICA IS TO
MAINTAIN ITS FOOTHOLD THROUGH DAY 05. LATER IN THE CYCLE IT IS TO
CENTER ON A CLOSED HIGH OVER THE NORTHEAST CARIBBEAN ISLES. THE
MID LEVEL RIDGE IS TO SUSTAIN A TRADE WINDS CAP ACROSS THE
BASIN...WITH PWAT MINIMA ACROSS THE NORTHERN CARIBBEAN ISLES EARLY
IN THE CYCLE TO QUICKLY EXPAND INTO THE SOUTHERN CARIBBEAN TO
NORTHERN SOUTH AMERICA. AT LOW LEVELS THIS IS TO SUSTAIN A RIDGE
OVER THE GULF OF MEXICO/NORTH OF THE ISLANDS EARLY IN THE CYCLE.
BUT...THROUGH FRIDAY MORNING IT IS TO MIGRATE EAST INTO THE
WESTERN ATLANTIC. EARLY IN THE CYCLE THIS IS TO SUSTAIN A FRESH
NORTHEASTERLY FLOW ACROSS EASTERN HISPANIOLA-PUERTO RICO-LEEWARD
ISLANDS. BUT AS THE RIDGE RELOCATES TO THE WESTERN ATLANTIC THE
WINDS WILL SHIFT TO THE EAST. OVERALL...MID LEVEL RIDGE PATTERN IS
TO GENERALLY FAVOR FAIR WEATHER CONDITIONS DURING THE NEXT FEW
DAYS...WITH LIGHT TRADE WIND SHOWERS TO PESTER THE LESSER
ANTILLES-PUERTO RICO AND NORTHERN HISPANIOLA FROM TIME TO TIME.

AS THE MID LEVEL RIDGE HOLDS OVER THE CARIBBEAN BASIN...MID LEVEL
SHORT WAVE PERTURBATIONS ON THE SOUTHERN STREAM ARE TO PROPAGATE
ACROSS NORTHERN MEXICO/SOUTHERN USA OVER THE NEXT FEW DAYS...WITH
ONE TO ENTER NORTHWEST MEXICO LATER THIS EVENING AND ANOTHER
AROUND MIDDAY ON SATURDAY. THESE ARE TO TRIGGER ISOLATED
CONVECTION ACROSS NORTHERN BAJA PENINSULA-NORTHERN SONORA WITH
ACCUMULATION OF 00-05MM/DAY. AS THE SHORT WAVE PERTURBATIONS
MIGRATE TO THE CENTRAL USA...THESE ARE TO INTERACT WITH A FRONT
OVER THE SOUTHERN USA/NORTHERN GULF OF MEXICO...TRIGGERING FRONTAL
LOWS ALONG THIS BOUNDARY. BUT THESE WILL NOT BE STRONG ENOUGH TO
SUSTAIN SIGNIFICANT DISPLACEMENT OF THE FRONT OVER THE NEXT FEW
DAYS. AS A RESULT...FRONTAL CONVECTION OVER NORTHEAST MEXICO WILL
BE LIGHT...WITH RAINFALL AMOUNTS OF 00-05MM/DAY AND WIDELY
ISOLATED MAXIMA OF 10MM. HIGHER AMOUNTS... HOWEVER...ARE EXPECTED
ACROSS THE YUCATAN PENINSULA...WHERE UNDER INFLUENCE OF A
PREFRONTAL TROUGH EXPECTING SCATTERED CONVECTION ACROSS
BELIZE-QUINTANA ROO EARLY ON FRIDAY...TO RESULT IN RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. ON SATURDAY MAXIMA
INCREASES TO 15-30MM IN SCATTERED CONVECTION. THROUGH SUNDAY THE
FOCUS OF THE CONVECTION SHIFTS TO CAMPECHE/TABASCO-YUCATAN...WITH
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM.

SOUTH OVER THE CARIBBEAN...STRENGTHENING MID LEVEL RIDGE IS TO
ALSO FAVOR EROSION OF AVAILABLE MOISTURE ACROSS SOUTHERN CENTRAL
AMERICA-NORTHERN SOUTH AMERICA. ACROSS PANAMA-COSTA RICA ACTIVITY
WANES THROUGH FRIDAY MORNING...WITH RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM IN DIURNAL CONVECTION. ITCZ
CONVERGENCE OVER COLOMBIA WILL LIMIT TO EJE CAFETERO/THE CAUCA
VALLEY...WITH RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM
OVER EJE CAFETERO...AND 05-10MM/DAY AND ISOLATED MAXIMA OF 15-20MM
ON THE CAUCA/CAUCA VALLEY TO THE SOUTH. THE ATLANTIC
ITCZ...MEANWHILE...IS TO MEANDER SOUTH ACROSS THE SOUTHERN GUIANAS
TO VENEZUELA...WITH MOST ACTIVE CONVECTION ACROSS AMAPA IN
BRASIL-THE SOUTHERN GUIANAS TO AMAZONIA IN VENEZUELA. IN THIS AREA
EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM
THROUGH FRIDAY MORNING. MOISTURE THEN SURGES LATER ON SATURDAY...
WITH CONVECTION ALONG THE COAST TO RESULT IN ACCUMULATION OF
05-10MM/DAY WITH  MAXIMA OF 15-25MM BETWEEN NORTHERN SURINAME AND
EASTERN FRENCH GUIANA. ACROSS NORTHERN GUYANA TO NORTHEAST
VENEZUELA...TRADE WIND CONVERGENCE WILL FAVOR RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM.

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)
$$





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