Prognostic Meteorological Discussion
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FXCA20 KWBC 251825
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
225 PM EDT WED APR 25 2018

TROPICAL DISCUSSION FROM APR 25/12 UTC: BROAD POLAR TROUGH OVER
THE EASTERN USA MOVES TO THE WESTERN ATLANTIC EARLY IN THE
CYCLE...WITH MID/UPPER LEVEL TROUGH FORECAST TO THEN LIFT OVER A
RIDGE TO THE EAST. A SECONDARY MID/UPPER LEVEL TROUGH
FOLLOWS...WITH AXIS FORECAST TO AMPLIFY ACROSS THE CENTRAL USA TO
THE NORTHEAST STATES OF MEXICO LATER TODAY. THE TROUGH IS TO THEN
AMPLIFY ACROSS THE GULF OF MEXICO TO THE YUCATAN/SOUTHERN STATES
OF MEXICO ON THURSDAY... FOCUSING CYCLONIC VORTICITY AND SHORT
WAVE ENERGY ACROSS WESTERN CUBA AND THE NORTHWEST BAHAMAS ON
FRIDAY. AT LOW LEVELS...A SURFACE FRONT MEANDERS ACROSS THE
NORTHWEST BAHAMAS-WESTERN CUBA/STRAITS OF FLORIDA-NORTHEAST
MEXICO/RIO BRAVO BASIN. BOUNDARY IS TO REMAIN NEARLY STATIONARY
WHILE GRADUALLY WEAKENING ON THURSDAY. A NEW FRONT
FOLLOWS...STREAMING ACROSS TEXAS LATER THIS EVENING...INTO THE
NORTHWEST GULF OF MEXICO ON THURSDAY MORNING. ON FRIDAY THE
BOUNDARY CONTINUES ACROSS THE FLORIDA PENINSULA INTO THE NORTHERN
YUCATAN...WHILE TRAILING TO NORTHEAST MEXICO. THE FRONT ENTERS THE
NORTHWEST BAHAMAS EARLY ON SATURDAY MORNING.

AS THE MID LEVEL TROUGH DEEPENS ACROSS TEXAS TO NORTHEAST MEXICO
THIS IS TO TRIGGER SCATTERED DEEP CONVECTION EARLY IN THE
CYCLE...TO SUSTAIN RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF
30-60MM. ON THURSDAY THE FOCUS OF THE CONVECTION WILL SHIFT TO
VERACRUZ WHERE IT IS TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-45MM. OVER CHIAPAS-TABASCO-NORTHERN YUCATAN THE UPPER
LEVEL TROUGH IS TO ALSO TRIGGER MODERATE TO HEAVY RAINFALL AMOUNTS
ON THURSDAY WITH ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF
30-60MM. ACROSS BELIZE-NORTHERN GUATEMALA AND QUINTANA ROO IN THE
YUCATAN THIS IS TO TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-25MM ON FRIDAY...INCREASING TO 10-15MM/DAY AND MAXIMA
OF 20-45MM ON SATURDAY. THE AMPLIFYING TROUGH IS TO ALSO ENHANCE
DIURNAL CONVECTION ALONG THE CONTINENTAL DIVIDE OVER SOUTHERN
CHIAPAS TO SOUTHERN GUATEMALA ON THURSDAY...FAVORING RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. ACTIVITY BUILDS
ACROSS EL SALVADOR/SOUTHERN HONDURAS ON THURSDAY-FRIDAY...WITH
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-45MM/DAY. AS THE
FRONT MEANDERS OVER THE NORTHWEST BAHAMAS-WESTERN CUBA...THIS IS
TO FAVOR SCATTERED CONVECTION WITH ACCUMULATION OF 05-10MM/DAY AND
MAXIMA OF 15-25MM/DAY. THROUGH FRIDAY...AS A SUBTROPICAL JET
MAXIMA ROUNDS THE BASE OF THE UPPER LEVEL TROUGH...FAVORING A
DIVERGENT PATTERN ALOFT...CONVECTION ACROSS WESTERN CUBA AND THE
NORTHWEST BAHAMAS INCREASES TO 15-20MM/DAY AND MAXIMA OF 35-70MM.
ON SATURDAY EXPECTING ADDITIONAL RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-45MM. NOTE THAT THIS IS TO COINCIDE WITH
FAVORABLE MJO ENVIRONMENTAL CONDITIONS...THUS LEADING TO A HIGHER
RISK OF ORGANIZED DEEP CONVECTION.

DEEPENING MID/UPPER LEVEL TROUGH ACROSS THE EASTERN USA IS TO
GRADUALLY INDUCE THE NORTHWARD AMPLIFICATION OF A RIDGE FROM THE
EASTERN CARIBBEAN INTO THE ATLANTIC ALONG 60W/70W. THE RIDGE IS TO
GRADUALLY BUILD THROUGH FRIDAY MORNING...AND IT IS TO THEN HOLD
THROUGHOUT THE WEEKEND. AS THE RIDGE INTENSIFIES...IT IS TO
STRENGTHEN THE TRADE WINDS CAP ACROSS THE NORTHEAST CARIBBEAN
ISLES...WITH TRADE WINDS CAP TO SETTLE AROUND 800 HPA EARLY ON
FRIDAY MORNING. THIS WILL BE ACCOMPANIED BY THE RAPID EROSION OF
AVAILABLE WATER. ACROSS PUERTO RICO MOST INTENSE IS EXPECTED ON
THURSDAY WHEN PLUME OF TROPICAL MOISTURE LIFTS ACROSS THE FORECAST
AREA...TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-30MM. THROUGH FRIDAY THIS DECREASES TO 00-05MM/DAY IN ISOLATED
DIURNAL CONVECTION. HIGHER AMOUNTS ARE EXPECTED ACROSS
HISPANIOLA...WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF
20-30MM/DAY.

DOWNSTREAM FROM THIS RIDGE...A 500 HPA LOW NEAR 30N 47W EXTENDS A
TROUGH TO THE EASTERN CARIBBEAN/NORTHERN GUIANAS. THE BROAD TROUGH
PATTERN IS TO GENERALLY HOLD DURING THE NEXT FEW DAYS. SOUTH OF
THIS AXIS...THE SUBEQUATORIAL RIDGE EXTENDS WEST ACROSS THE
TROPICAL ATLANTIC TO NORTHERN SOUTH AMERICA/SOUTHERN CENTRAL
AMERICA. THE RIDGE ALOFT IS VENTING ITCZ/NET RELATED CONVECTION
OVER THE GUIANAS-SOUTHERN VENEZUELA-AMAZONIA IN COLOMBIA. OVER THE
GUIANAS EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-45MM...WITH A SLIGHT INCREASE ON FRIDAY-SATURDAY. OVER AMAZONAS
IN SOUTHERN VENEZUELA EXPECTING ACCUMULATION OF 15-20MM/DAY AND
MAXIMA OF 30-60MM/DAY THROUGH FRIDAY MORNING...DECREASING TO
MAXIMA OF 25-50MM/DAY ON FRIDAY-SATURDAY. ON THE ANDEAN REGION OF
COLOMBIA EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-30MM/DAY. THROUGH FRIDAY THIS INCREASES TO MAXIMA OF
20-40MM/DAY. OVER PANAMA-COSTA RICA...THE RIDGE ALOFT IS TO VENT
ITCZ RELATED CONVECTION...TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-35MM/DAY.

TROPICAL/EASTERLY WAVES/TRADE WIND SURGES INITIALIZED AT 12UTC:
INITIAL 24    36    48    60    72    84    96         TYPE    SOF
38W     40W   42W   44W   47W   50W   52W   55W         TW     15N
65W     68W   70W   72W   74W   76W   78W   80W         EW     14N
84W     86W   88W   DISSIPATES                          EW     11N

A TROPICAL WAVE ALONG 38W AND SOUTH OF 15N IS TO ENTER AMAPA IN
BRASIL/EASTERN FRENCH GUIANA ON FRIDAY EVENING...TO FAVOR RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM.

AN EASTERLY WAVE ALONG 65W AND SOUTH OF 14N IS TO ENHANCE NET
RELATED CONVERGENCE ACROSS SOUTHERN VENEZUELA-SOUTHEAST COLOMBIA
TO FAVOR RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM/DAY
THROUGH THURSDAY EVENING. AS IT MOVES INTO WESTERN COLOMBIA ON
FRIDAY EXPECTING ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF
20-40MM...WITH MOST ACTIVE ALONG THE ANDES. OVER PANAMA EXPECTING
SIMILAR RAINFALL AMOUNTS ON SATURDAY.

AN EASTERLY WAVE ALONG 84W AND SOUTH OF 11N IS TO ENHANCE ITCZ
RELATED CONVECTION ACROSS HONDURAS/EL SALVADOR LATER TODAY...TO
TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.

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

$$





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