Prognostic Meteorological Discussion
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FXCA20 KWBC 251559
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1159 AM EDT FRI MAY 25 2018

AT 15 UTC SUBTROPICAL STORM ALBERTO CENTERED NEAR 19.7N
86.8W...WITH MAXIMUM SUSTAINED WINDS OF 35KT AND MINIMAL CENTRAL
PRESSURE OF 1005 HPA. THE STORMS IS MOVING TO THE NORTH-NORTHEAST
AT 05KT.

TROPICAL DISCUSSION FROM MAY 24/12 UTC: CONSISTENT WITH PREVIOUS
FORECASTS...A MID/UPPER LEVEL HIGH OVER SOUTHWEST MEXICO IS TO
EXTENDS A RIDGE NORTH ACROSS NORTHERN MEXICO TO THE SOUTHWEST USA
DURING THE NEXT FEW DAYS. A TROUGH TO THE EAST...MEANWHILE...IS TO
EXTEND ACROSS THE GULF ALONG 90W TO GUATEMALA/HONDURAS. AS THE
RIDGE TO THE WEST HOLDS...THE TROUGH TO THE EAST IS TO ALSO
PERSIST. PER NHC GUIDANCE...THE TROUGH IS TO THEN STEER
SUBTROPICAL STORM ALBERTO NORTH ACROSS THE YUCATAN CHANEL BY
DAYBREAK ON SATURDAY...TO THEN MEANDER NORTH ACROSS THE EASTERN
GULF OF MEXICO. OVER WESTERN CUBA AND NORTHERN QUINTANA ROO IN THE
YUCATAN THIS IS TO CONTINUE FAVORING HEAVY RAINFALL AMOUNTS...WITH
STORM TOTAL AMOUNTS OF 250-400MM. FURTHERMORE...OVER WESTERN CUBA
EXPECTING LOCALIZED MAXIMA OF 500-600MM. OVER THE CAYMAN
ISLES-CENTRAL CUBA FEEDER BAND CONVERGENCE WILL FAVOR RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM. ON SATURDAY-SUNDAY
EXPECTING ADDITIONAL RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM. OVER JAMAICA EXPECTING LESSER AMOUNTS...WITH ACCUMULATION
OF 05-10MM/DAY AND MAXIMA OF 15MM DURING THE DAY
TODAY...INCREASING TO 10-15MM/DAY AND MAXIMA OF 20-35MM ON
SATURDAY...WHILE ON SUNDAY IT IS TO PEAK AT 15-20MM/DAY.

THE DEEP TROUGH...AS IT BOTTOMS OUT ACROSS NORTHERN CENTRAL
AMERICA...SUSTAINS THE NORTHWARD MODULATION OF THE EASTERN PACIFIC
ITCZ ACROSS NICARAGUA TO THE CENTRAL CARIBBEAN. AS SUBTROPICAL
STORM ALBERTO BECOMES BETTER ORGANIZED TO THE NORTH THIS WILL THEN
FAVOR A MOIST WESTERLY FLOW ACROSS THE EASTERN PACIFIC THAT IS TO
CONVERGE ALONG THE CONTINENTAL DIVIDE BETWEEN EL SALVADOR/SOUTHERN
HONDURAS AND WESTERN NICARAGUA. IN THIS AREA EXPECTING RAINFALL
AMOUNTS OF 20-30MM/DAY AND MAXIMA OF 50-100MM/DAY. OVER NORTHEAST
HONDURAS/NICARAGUA EXPECTING ACCUMULATION OF 10-15MM/DAY AND
MAXIMA OF 20-35MM/DAY. OVER COSTA RICA/SOUTHERN NICARAGUA...IN A
MOIST WESTERLY FLOW...INITIALLY EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40MM. ON SATURDAY-SUNDAY THIS SURGES
TO 20-30MM/DAY AND MAXIMA OF 50-100MM...WHILE ON SUNDAY TO MONDAY
EXPECTING ACCUMULATION OF 25-50MM/DAY AND MAXIMA OF 75-125MM. OVER
NORTHERN COLOMBIA/NORTHWEST VENEZUELA AND PANAMA EXPECTING
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. THROUGH
MONDAY THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER
EASTERN COLOMBIA-SOUTHERN VENEZUELA...MEANWHILE...EXPECTING
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM/DAY. LATER
ON MONDAY THE DAILY MAXIMA DECREASES TO 25-50MM.

AS THE MID/UPPER LEVEL TROUGH DEEPENS ACROSS THE GULF OF MEXICO TO
THE WESTERN CARIBBEAN/CENTRAL AMERICA...THIS IS TO THEN FAVOR THE
GRADUAL AMPLIFICATION OF A RIDGE ACROSS THE CENTRAL CARIBBEAN TO
THE WESTERN ATLANTIC. AS THE RIDGE BUILDS...MODELS NOW AGREE ON A
FAIRLY STRONG TRADE WINDS CAP TO BRIEFLY ESTABLISH ACROSS THE
NORTHEAST CARIBBEAN ISLANDS EARLY IN THE CYCLE. THE INVERSION IS
FORECAST TO DROP FROM AROUND 650/700 HPA EARLY TODAY TO AROUND 750
HPA BY MIDDAY ON SATURDAY. AT LOW LEVELS...BROAD RIDGE OVER THE
ATLANTIC BASIN FAVORS A BRISK EAST-SOUTHEAST FLOW ACROSS THE
NORTHEAST CARIBBEAN. THIS IS ADVECTING SHALLOW MOISTURE ACROSS THE
ISLAND CHAIN TO PUERTO RICO-VIRGIN ISLES AND PORTIONS OF
HISPANIOLA... WHERE IT IS TO FEED DIURNAL CONVECTION DURING THE
NEXT COUPLE OF DAYS. OVER THE NORTHEAST CARIBBEAN ISLES THIS IS TO
GENERALLY FAVOR SCATTERED SHALLOW CONVECTION WITH ACCUMULATION OF
10-15MM/DAY...WITH MAXIMA OF 20-35MM TO CLUSTER OVER WESTERN
PUERTO RICO AND CENTRAL HISPANIOLA.

SIMULTANEOUSLY...AS THE MID/UPPER LEVEL RIDGE BUILDS ACROSS THE
WESTERN ATLANTIC...THIS IS TO THEN INDUCE THE SOUTHWARD
AMPLIFICATION OF A TROUGH TO THE EAST...WITH AXIS TO ENTER THE
NORTHEAST CARIBBEAN ON SUNDAY-MONDAY. THIS THEN EVOLVES INTO A
CLOSED LOW TO THE NORTH-NORTHEAST OF THE LEEWARD ISLES...MEANWHILE
FAVORING WEAK CYCLONIC VORTICITY ADVECTION ACROSS PUERTO
RICO-VIRGIN ISLES-NORTHERN LEEWARD ISLANDS. AT 250 HPA A JET
MAXIMA IS TO THEN ROUND THE BASE OF THE TROUGH LATER ON
SUNDAY...WITH DIVERGENCE ON ITS RIGHT ENTRANCE REGION TO THEN VENT
DEEP CONVECTIVE DEVELOPMENT. AT LOW LEVELS...TROPICAL WAVE
STREAMING ACROSS THE EASTERN CARIBBEAN WILL SUSTAIN A MOIST PLUME
ACROSS THE ISLAND CHAIN THAT IS TO THEN FEED CONVECTIVE
DEVELOPMENT ACROSS PUERTO RICO/VIRGIN ISLES AND THE DOMINICAN
REPUBLIC. OVER THE LEEWARD/VIRGIN ISLES TO EASTERN PUERTO RICO
THIS IS TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15MM. OVER WESTERN PUERTO RICO AND THE DOMINICAN REPUBLIC
EXPECTING ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-45MM...WITH
LOCALLY HIGHER AMOUNTS HIGHLY PROBABLE.

AT 250 HPA...A CELL OF THE SUBEQUATORIAL RIDGE TO THE SOUTH
DOMINATES THE UPPER LEVEL FLOW FROM THE TROPICAL ATLANTIC WESTWARD
TO THE GUIANAS/SOUTHERN VENEZUELA. THIS IS VENTING CONVECTION
ALONG THE ITCZ/NEAR EQUATORIAL TROUGH. ACROSS FRENCH
GUIANA-SURINAME EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM. ON SATURDAY-SUNDAY THIS INCREASES TO
15-20MM/DAY AND MAXIMA OF 30-60MM...WHILE ON SUNDAY IT IS TO PEAK
AT 20-40MM. ACROSS GUYANA TO EASTERN VENEZUELA EXPECTING RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM.

TROPICAL/EASTERLY WAVES/TRADE WIND SURGES INITIALIZED AT 12UTC:
INITIAL 24    36    48    60    72    84    96        TYPE
SOF
54W     57W   60W   63W   66W   69W   72W   75W        TW
18N
80W     82W   83W   DISSIPATES                         TW
17N

TROPICAL WAVE ALONG 54W AND SOUTH OF 18N IS TO TRIGGER SCATTERED
CONVECTION ACROSS SURINAME TO GUYANA EARLY IN THE CYCLE...TO
RESULT IN RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM.
ON SATURDAY THIS IS TO TRIGGER SCATTERED CONVECTION ACROSS
EASTERN-CENTRAL VENEZUELA...WITH ACCUMULATION OF 15-20MM/DAY AND
MAXIMA OF 30-60MM. OVER THE LESSER ANTILLES EXPECTING RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. ON SUNDAY IT IS TO
SUSTAIN A SURGE IN ACTIVITY ACROSS PUERTO RICO-DOMINICAN REPUBLIC
WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-45MM. ACROSS
EASTERN COLOMBIA EXPECTING ACCUMULATION OF 15-20MM/DAY AND MAXIMA
OF 30-60MM. ON MONDAY THIS DECREASES TO 15-20MM/DAY AND MAXIMA OF
25-50MM...WHILE OVER WESTERN COLOMBIA/ANDEAN REGION EXPECTING
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER HAITI THIS
IS TO THEN TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-40MM.

A TROPICAL WAVE ALONG 80W AND SOUTH OF 17N IS FORECAST TO
DISSIPATE ON SATURDAY. MEANWHILE...OVER PANAMA-COSTA RICA THIS IS
TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM
THROUGH SATURDAY MORNING. THE MOST INTENSE TO CLUSTER ALONG THE
CONTINENTAL DIVIDE.

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

$$





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