Prognostic Meteorological Discussion
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048
FXCA20 KWBC 231832
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
232 PM EDT TUE MAY 23 2017

TROPICAL DISCUSSION FROM MAY 23/12 UTC: POLAR TROUGH DEEPENS
ACROSS THE CENTRAL USA TO THE GULF OF MEXICO THROUGH WEDNESDAY
MORNING. ON THURSDAY THE TROUGH MEANDERS EAST ACROSS THE EASTERN
USA WHILE LIFTING OVER A RIDGE TO THE EAST. AT LOW LEVELS THE
ASSOCIATED FRONT MOVES TO SOUTH TEXAS/RIO BRAVO BASIN LATER ON
TUESDAY/EARLY WEDNESDAY MORNING. IT THEN MEANDERS INTO THE
NORTHWEST GULF-NORTHERN TAMAULIPAS BY MIDMORNING ON WEDNESDAY.
EARLY ON THURSDAY THE FRONT MOVES TO CENTRAL FLORIDA...WHILE
TRAILING ACROSS THE GULF OF MEXICO TO NORTHERN VERACRUZ. THE
FRONTAL BOUNDARY IS TO THEN MEANDER ACROSS THE NORTHWEST BAHAMAS
ON THURSDAY...WHILE TRAILING END OVER THE GULF STARTS TO
WEAKEN/FRONTOLIZE. ACROSS THE NORTHEAST STATES OF MEXICO THIS WILL
TRIGGER SCATTERED CONVECTION ON TUESDAY-WEDNESDAY...WITH RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-30MM. OVER CENTRAL MEXICO
THIS IS TO ENHANCE DIURNAL CONVECTION TO FAVOR RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-25MM. OVER THE NORTHWEST
BAHAMAS...PREFRONTAL CONVECTION LATER ON WEDNESDAY WILL RESULT IN
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. ON THURSDAY
THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-35MM.
ALSO...PREFRONTAL CONVECTION OVER WESTERN CUBA/ISLAND OF YOUTH ON
WEDNESDAY AND THURSDAY WILL RESULT IN RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15MM. FURTHERMORE...AS IT MEANDERS OVER
THE GULF...THE POLAR FRONT WILL INDUCE A PREFRONTAL TROUGH ACROSS
THE YUCATAN PENINSULA ON WEDNESDAY. THE TROUGH WILL ENHANCE LOW
LEVEL MOISTURE CONVERGENCE ACROSS YUCATAN-QUINTANA ROO MEXICO TO
TRIGGER RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM.

THE AMPLIFYING POLAR TROUGH WILL PRESS AGAINST A MID LEVEL RIDGE
TO THE SOUTH. EARLY IN THE CYCLE THE RIDGE WILL EXTEND FROM A
CLOSED HIGH SOUTH OF THE BAJA PENINSULA TO THE CENTRAL/SOUTHERN
STATES OF MEXICO/NORTHERN CENTRAL AMERICA. UNDER PRESSURE FROM THE
AMPLIFYING TROUGH THE RIDGE IS TO NEARLY COLLAPSE LATER ON
WEDNESDAY. ON THURSDAY-FRIDAY...AS THE POLAR TROUGH LIFTS...THE
RIDGE BOUNCES BACK. BUT AS THE RIDGE WEAKENS EARLY IN THE
CYCLE...EXPECTING AN INCREASE IN DIURNAL CONVECTION BETWEEN
SOUTHERN MEXICO AND CENTRAL AMERICA. OVER CHIAPAS IN SOUTHERN
MEXICO-GUATEMALA-EL SALVADOR/SOUTHERN HONDURAS INITIALLY EXPECTING
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. THROUGH
THURSDAY THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-45MM. OVER
EASTERN NICARAGUA/NORTHEAST HONDURAS EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM. OVER SOUTHERN NICARAGUA-COSTA
RICA AND WESTERN PANAMA EXPECT RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-25MM. ON WEDNESDAY-THURSDAY THIS INCREASES TO
10-15MM/DAY AND MAXIMA OF 20-35MM.

SIMULTANEOUSLY...DEEPENING POLAR TROUGH OVER NORTH AMERICA WILL
SUSTAIN THE NORTHWARD AMPLIFICATION OF A MID LEVEL RIDGE ACROSS
THE EASTERN CARIBBEAN/NORTHERN SOUTH AMERICA TO THE WESTERN
ATLANTIC. THE RIDGE IS TO ANCHOR ON A MEANDERING HIGH NORTH OF
PUERTO RICO/EASTERN HISPANIOLA. THIS FAVORS A FAIRLY STRONG CAP
INVERSION AND EROSION OF AVAILABLE MOISTURE. AT LOW LEVELS...A
HIGH TO THE SOUTHEAST OF BERMUDA/NORTH OF THE LEEWARD ISLES
ANCHORS A RIDGE OVER THE WESTERN ATLANTIC. THIS FAVORS A BRISK
SOUTHEASTERLY FLOW ACROSS THE EASTERN-CENTRAL CARIBBEAN...WHILE
ALSO ADVECTING A DRY SAHARAN AIR LAYER ACROSS THE FORECAST AREA.
THIS PATTERN IS EXPECTED TO HOLD DURING THE NEXT 72-84
HRS...FAVORING FAIR WEATHER CONDITIONS ACROSS THE
FRENCH-LEEWARD/VIRGIN ISLES-PUERTO RICO AND PORTIONS OF
HISPANIOLA.

AS THE MID LEVEL RIDGE MEANDERS OVER THE WESTERN ATLANTIC...IT IS
TO SLOWLY INDUCE THE SOUTHWARD AMPLIFICATION OF A TUTT EAST OF THE
ISLANDS LATER ON WEDNESDAY/EARLY ON THURSDAY. THIS EVOLVES INTO A
CLOSED LOW EAST OF THE LEEWARD ISLES LATER ON THURSDAY/FRIDAY
MORNING...WHERE IT IS TO REMAIN THROUGHOUT THE WEEKEND. AS IT
PRESSES AGAINST THE RIDGE TO THE WEST...THE TRADE WINDS CAP
RELAXES ITS FOOTHOLD ACROSS THE NORTHEAST CARIBBEAN ISLES...WITH
SHALLOW CONVECTIVE INSTABILITY TO SPREAD ACROSS THE NORTHEAST
CARIBBEAN DURING THE WEEKEND. IN RESPONSE...THE GFS AND ECMWF BOTH
SHOW AN INCREASE IN CONVECTION BETWEEN THE LEEWARD ISLES AND
PUERTO RICO LATER IN THE WEEK...WITH RAINFALL AMOUNTS OF
00-05MM/DAY AND ISOLATED MAXIMA OF 10MM IN SHALLOW CONVECTION.

FURTHERMORE...AN ITCZ/NET RELATED MOIST PLUME TO THE SOUTH IS
EXPECTED TO LIFT NORTH ALONG THE FRINGES OF THE LOW LEVEL RIDGE
INTO TRINIDAD AND TOBAGO EARLY IN THE CYCLE...WHERE IT WILL FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM THROUGH
WEDNESDAY MORNING. MOISTURE CONVERGING ALONG THE NEAR EQUATORIAL
TROUGH OVER THE GUIANAS WILL RESULT IN RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40MM ACROSS NORTHERN GUYANA/NORTHEAST
VENEZUELA EARLY IN THE PERIOD. THROUGH THURSDAY THIS BUILDS SOUTH
ALONG THE COAST OF SURINAME TO NORTHERN FRENCH GUIANA WHERE IT IS
TO ALSO TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-40MM. OVER VENEZUELA IT IS TO FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM. ACROSS EASTERN-CENTRAL COLOMBIA
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM...WHILE OVER WESTERN COLOMBIA INITIALLY EXPECTING RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM...INCREASING TO
20-40MM LATER ON WEDNESDAY THROUGH THURSDAY.

TRADE WINDS SURGE INITIALIZED AT 12UTC:
INITIAL   24     36     48     60     72     84     96       TYPE
81W      83W    85W    86W     DISSIPATES                    TWS

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24     36     48     60     72     84     96       TYPE
28W      30W    34W    37W    39W    41W    44W     49W      TW
49W      52W    55W    58W    61W    63W    67W     70W      TW
79W      80W    82W    84W    87W    89W    91W     93W      EW
91W      94W    97W    DISSIPATES                            TW

A TRADE WIND SURGE IS INITIALIZED ALONG 81W...WITH DENSE SAHARAN
AIR LAYER/DUST STILL TRAILING ACROSS THE EASTERN CARIBBEAN. THE
SURGE IS WEAKENING RAPIDLY...AND BY THE END OF DAY ON WEDNESDAY IT
IS FORECAST TO DISSIPATE. MEANWHILE...AS IT ENTERS EASTERN
NICARAGUA EARLY ON WEDNESDAY IT IS TO TRIGGER RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM.

TROPICAL WAVE ALONG 28W WILL CONFINE TO THE ATLANTIC ITCZ DURING
THE NEXT FOUR DAYS.

TROPICAL WAVE ALONG 49W REACHES EASTERN FRENCH GUIANA LATER
TODAY...TO TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM. OVER SURINAME TO GUYANA...IN INTERACTION WITH THE
ATLANTIC ITCZ...EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-35MM ON WEDNESDAY. ACROSS VENEZUELA THIS IS TO THEN
FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM ON
WEDNESDAY TO THURSDAY.

AN EASTERLY WAVE ALONG 79W IS TO INTERACT WITH THE EASTERN PACIFIC
ITCZ OVER WESTERN COLOMBIA/DARIEN IN EASTERN PANAMA TO TRIGGER
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. ACROSS
COSTA RICA/WESTERN PANAMA AND SOUTHERN NICARAGUA IT IS TO THEN
FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM ON
WEDNESDAY TO THURSDAY. . AS IT PULLS ACROSS EL SALVADOR/SOUTHERN
HONDURAS ON THURSDAY EXPECT RAINFALL ACCUMULATION OF 10-15MM/DAY
AND MAXIMA OF 20-45MM.

TROPICAL WAVE ALONG 91W ENHANCES CONVECTION ACROSS SOUTHEAST
STATES OF MEXICO ON TUESDAY TO WEDNESDAY...TO TRIGGER RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. THE WAVE IS TO THEN
DISSIPATE LATER ON WEDNESDAY.

GAJADHAR...SLMS (SAINT LUCIA)
SUBRATH-ALI...TTMS (TRINIDAD AND TOBAGO)
DAVISON/GALVEZ...WPC (USA)
$$





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