Prognostic Meteorological Discussion
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FXCA20 KWBC 191831
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
230 PM EDT THU APR 19 2018

TROPICAL DISCUSSION FROM APR 19/12 UTC: OVER WESTERN PORTIONS OF
THE DOMAIN...A 500 HPA HIGH OVER COLIMA/NAYARIT IN SOUTHWEST
MEXICO EXTENDS A RIDGE ACROSS THE CENTRAL/NORTHERN STATES OF
MEXICO TO THE WESTERN USA. POLAR TROUGH ENTERING THE WESTERN USA
IS TO PRESS AGAINST THIS AXIS...WITH RIDGE FORECAST TO GRADUALLY
FLATTEN TO THE NORTH OF 28N THROUGH SATURDAY EVENING. AT LOW
LEVELS THIS IS TO SUSTAIN A SURFACE FRONT THAT SURGES ACROSS TEXAS
TO THE NORTHERN STATES OF COAHUILA-TAMAULIPAS ON SUNDAY EVENING.
PREFRONTAL CONVECTION ALONG THE RIO BRAVO BASIN WILL SUSTAIN
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM.

EAST OF THE MID/UPPER LEVEL RIDGE...A DIGGING POLAR TROUGH EXITS
THE EASTERN USA LATER TODAY. THIS REACHES MAXIMUM AMPLITUDE ON
FRIDAY WHEN IT IS FORECAST TO BOTTOM OUT OVER THE NORTHWEST
BAHAMAS ON FRIDAY...WITH AXIS TO THEN PULL TO THE EAST-NORTHEAST
ON SATURDAY TO SUNDAY. AT LOW LEVELS THIS WILL SUSTAIN A SURFACE
FRONT THAT TRAILS INTO NORTHEASTERN MEXICO/RIO BRAVO BASIN LATER
TODAY. BOUNDARY IS TO THEN MOVE ACROSS CENTRAL FLORIDA EARLY ON
SATURDAY MORNING...REACHING THE NORTHWEST BAHAMAS LATER IN THE DAY
WHILE ITS TRAILING END RETROGRESSES TO THE SOUTHERN USA. AS IT
ENTERS THE NORTHWEST BAHAMAS IT IS TO THEN REMAIN NEARLY
STATIONARY THROUGH MONDAY MORNING. OVER NORTHEAST STATES OF MEXICO
THIS IS TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-30MM EARLY IN THE CYCLE. OVER THE NORTHWEST BAHAMAS EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM ON SATURDAY. ON
SUNDAY THE MAXIMA INCREASES TO 15-20MM IN SCATTERED CONVECTION.
ACROSS CUBA THIS IS TO SUSTAIN A PREFRONTAL SHER LINE ON
FRIDAY-SATURDAY...TO ENHANCE LOW LEVEL MOISTURE CONVERGENCE ACROSS
CENTRAL CUBA WHILE TRIGGERING RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15MM. HIGHER AMOUNTS ARE EXPECTED TO THE EAST...WITH
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-35MM ON FRIDAY.
THROUGH SUNDAY THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15MM.

A MID/UPPER LEVEL SHORT WAVE TROUGH ON THE SOUTHERN STREAM ALSO
EXTENDS ALONG THE FRINGES OF THE CONTINENTAL RIDGE...WITH AXIS
SOUTH ACROSS THE GULF OF MEXICO/ YUCATAN PENINSULA TO THE
GALAPAGOS ISLANDS. THE TROUGH IS TO MEANDER EAST INTO THE WESTERN
CARIBBEAN-CENTRAL AMERICA ON FRIDAY...WHERE IT IS TO GENERALLY
HOLD THROUGH THE WEEKEND. AT MID LEVELS THIS WILL INDUCE THE
NORTHWARD AMPLIFICATION OF A SHORT WAVE TROUGH ACROSS SOUTHERN
CENTRAL AMERICA TO THE CENTRAL CARIBBEAN JUST SOUTH OF JAMAICA
EARLY IN THE CYCLE. THIS IS FORECAST TO EVOLVE INTO A CLOSED LOW
JUST SOUTH OF THE ISLAND ON FRIDAY-SATURDAY. AS IT MEANDERS ACROSS
THE YUCATAN EARLY IN THE PERIOD THIS WILL ENHANCE CONVECTIVE
INSTABILITY. OVER GUATEMALA-BELIZE-CHIAPAS THIS IS TO FAVOR
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM...WHILE OVER
NORTHERN BELIZE-THE YUCATAN EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-30MM. ON FRIDAY FOCUS OF THE
CONVECTION SHIFTS TO NORTHERN HONDURAS-BELIZE WITH ACCUMULATION OF
05-10MM/DAY AND MAXIMA OF 15-25MM. ACROSS JAMAICA...UNDER
INFLUENCE OF THE MID LEVEL TROUGH...INITIALLY EXPECTING RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. ON FRIDAY THIS
INCREASES TO 15-20MM/DAY AND MAXIMA OF 25-50MM...WHILE ON SATURDAY
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM.
THROUGH SUNDAY THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15MM AS
THE UPPER TROUGH MEANDERS FARTHER EAST ACROSS THE CENTRAL
CARIBBEAN. THE TROUGH IS TO ALSO ENHANCE CONVECTION ACROSS
SOUTHERN CENTRAL AMERICA. ACROSS PANAMA-COSTA RICA INITIALLY
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-40MM...WITH MOST ACTIVE ALONG THE CARIBBEAN COASTAL PLAINS.
THIS BUILDS WEST ACROSS COSTA RICA TO SOUTHERN NICARAGUA ON
FRIDAY-SATURDAY...TO SUSTAIN RAINFALL AMOUNTS OF 15-20MM/DAY AND
MAXIMA OF 30-60MM. ON SUNDAY THIS DECREASES TO 10-15MM/DAY AND
MAXIMA OF 20-40MM. OVER NORTHEAST HONDURAS/NICARAGUA THIS WILL
TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.

FARTHER EAST...A 500/250 HPA HIGH OVER THE CENTRAL TROPICAL
ATLANTIC EXTENDS A RIDGE WEST TO THE GUIANAS/NORTHEAST VENEZUELA.
THIS RIDGE SLOWLY BUILDS WEST ACROSS VENEZUELA TO COLOMBIA ON
THURSDAY-FRIDAY. AS THE MID LEVEL RIDGE BUILDS ACROSS THE EASTERN
CARIBBEAN IT IS TO STRENGTHEN THE TRADE WINDS CAP...TO FAVOR A
DRYING TREND ACROSS THE FRENCH-LEEWARD ISLANDS TO PUERTO RICO
EARLY IN THE CYCLE. DEEPER INSTABILITY...HOWEVER...WILL PERSIST TO
THE SOUTH OF THIS AXIS ACROSS THE GUIANAS TO VENEZUELA. OVER THE
GUIANAS EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-30MM/DAY...WITH MOST ACTIVE ON FRIDAY-SUNDAY. ACROSS SOUTHERN
VENEZUELA ALSO EXPECTING ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF
20-30MM. THROUGH SATURDAY THIS INCREASES TO 15-20MM/DAY AND MAXIMA
OF 30-60MM. OVER AMAZONIA IN SOUTHERN COLOMBIA NEAR EQUATORIAL
TROUGH RELATED CONVERGENCE WILL SUSTAIN RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 30-60MM/DAY. ON THE ANDEAN
REGION/NORTHWEST COLOMBIA EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40MM/DAY. THROUGH SUNDAY THIS
DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-20MM.

TROPICAL/EASTERLY WAVES/TRADE WIND SURGES INITIALIZED AT 12UTC:
INITIAL 24    36    48    60    72    84    96         TYPE    SOF
54W     58W   61W   65W   68W   71W   73W   77W         TW     17N
71W     74W   76W   DISSIPATES                          INDCD  23N
76W     78W   80W   82W   84W   86W   88W   90W         TW     16N

A TROPICAL WAVE ALONG 54W AND SOUTH OF 17N IS TO ADVECT A PLUME OF
DEEP TROPICAL MOISTURE ACROSS THE GUIANAS. OVER FRENCH GUIANA THIS
IS TO TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-40MM ON THURSDAY. ACTIVITY BUILDS ACROSS SURINAME ON FRIDAY TO
FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. OVER
SOUTHERN GUYANA TO EASTERN VENEZUELA THIS IS TO THEN TRIGGER
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM ON
SATURDAY...WHILE OVER NORTHERN GUYANA-ORINOCO DELTA EXPECTING
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM. ACROSS
SOUTHERN/CENTRAL VENEZUELA EXPECTING RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 30-60MM ON SATURDAY. THIS BUILDS INTO
PIEDEMONTE LLANERO IN EASTERN COLOMBIA ON SUNDAY TO TRIGGER
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM.

AN INDUCED TROUGH ALONG 71W AND SOUTH OF 23N IS TO ENHANCE
CONVECTION ACROSS THE HISPANIOLA DURING THE DAY TODAY TO FAVOR
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 35-70MM. THIS THEN
DISSIPATES EARLY ON FRIDAY.

A TROPICAL WAVE ALONG 76W AND SOUTH OF 17N IS TO INTERACT WITH MID
LEVEL TROUGH OVER THE SOUTHERN CARIBBEAN TO ENHANCE CONVECTION
ACROSS PANAMA-COSTA RICA EARLY IN THE CYCLE. IN THIS AREA
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM.
ON FRIDAY CONVECTION BUILDS ACROSS COSTA RICA TO SOUTHERN
NICARAGUA TO SUSTAIN RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF
30-60MM. OVER NORTHEAST NICARAGUA/HONDURAS THIS IS TO THEN TRIGGER
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. THIS IS TO
AFFECT NORTHERN HONDURAS ON SATURDAY...AND SOUTHERN STATES OF
MEXICO ON SUNDAY.

HUDSON...MS (JAMAICA)
NIXON...BDM (THE BAHAMAS)
DAVISON/GALVEZ...WPC (USA)

$$





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