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FXCA20 KWBC 271823
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
223 PM EDT THU APR 27 2017

TROPICAL DISCUSSION FROM APRIL 27/12 UTC: AT 500 HPA...A CLOSED
HIGH SOUTH OF GUERRERO IN SOUTHWEST MEXICO ANCHORS A RIDGE OVER
THE EASTERN PACIFIC-CENTRAL AMERICA TO THE CENTRAL CARIBBEAN.
SHORT WAVE RIDGE PATTERN IS TO PERSIST NEARLY UNCHANGED OVER THE
NEXT TWO DAYS...BUT LATER DURING THE WEEKEND IT WILL WEAKEN FROM
THE WEST AS A DEEPENING POLAR TROUGH AMPLIFIES ACROSS THE
SOUTHEAST USA TO THE NORTHERN STATES OF MEXICO. THE MID LEVEL
RIDGE...AS IT MEANDERS OVER SOUTHERN MEXICO-CENTRAL AMERICA...WILL
SUSTAIN A WEAK INVERSION. THIS WILL BE STRONG ENOUGH TO DELAY
ONSET OF DIURNAL CONVECTION BUT NOT STRONG ENOUGH TO SUPPRESS IT.
MEANWHILE...OVER SOUTHERN MEXICO-EL SALVADOR/HONDURAS EXPECTING
AFTERNOON CONVECTION ALONG THE CONTINENTAL DIVIDE TO FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND ISOLATED MAXIMA OF 15-20MM.
HIGHER MOISTURE CONTENT IS EXPECTED TO THE SOUTH...WITH PWAT OF
40-50MM TO POOL ACROSS PANAMA-COSTA RICA TO WESTERN COLOMBIA. ON
THE CARIBBEAN COASTAL PLAINS OF COSTA RICA/WESTERN PANAMA TRADE
WIND CONVERGENCE WILL SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15MM. HIGHER AMOUNTS ARE EXPECTED ON THE PACIFIC SIDE OF
THE ISTHMUS...WHERE A SOUTHWESTERLY LOW LEVEL FLOW IS ENHANCING
MOISTURE TRANSPORT/CONVERGENCE. THIS WILL LEAD TO AN INCREASE IN
DEEP LAYER CONVECTIVE INSTABILITY ON SATURDAY...WITH GDI SHOWING
PEAK IN INSTABILITY BY MIDDAY ON SATURDAY. ITCZ RELATED CONVECTION
IS TO CLUSTER ALONG THE COAST BETWEEN THE NICOYA PENINSULA IN
NORTHWEST COSTA RICA AND THE AZUERO PENINSULA IN SOUTHERN PANAMA.
IN THIS AREA INITIALLY EXPECTING RAINFALL ACCUMULATION OF
15-20MM/DAY AND MAXIMA OF 25-50MM. THIS IS FORECAST TO GRADUALLY
INTENSIFY THROUGH SATURDAY EVENING...WHEN WE EXPECT RAINFALL
AMOUNTS OF 15-30MM/DAY AND MAXIMA OF 40-80MM.

OVER SOUTHWEST COLOMBIA...AS THE ITCZ MEANDERS NORTH ALONG THE
COAST...DIURNAL CONVECTION IS TO THEN FAVOR RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM/DAY. ON SUNDAY IT INCREASES TO
MAXIMA OF 20-30MM. OVER NORTHWESTERN COLOMBIA...AS ENHANCED BY THE
EASTERN PACIFIC ITCZ...INITIALLY EXPECTING RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 25-50MM. THROUGH SATURDAY MORNING THIS
IS ALSO FORECAST TO INCREASE TO 15-20MM/DAY AND MAXIMA OF
30-60MM...WITH LESSER AMOUNTS LATER DURING THE WEEKEND. ON THE
SIERRA NEVADA OVER NORTHERN COLOMBIA AND ACROSS NORTHWEST
VENEZUELA...EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA
OF 15-20MM. THROUGH SATURDAY/SUNDAY THIS INCREASES TO 10-15MM/DAY
AND MAXIMA OF 20-35MM. OVER SOUTHERN COLOMBIA...EAST OF THE
ANDES...UNDER INFLUENCE OF A SOUTHERN HEMISPHERE WIND SURGE OVER
BRASIL-PERU...CONVECTION WILL BECOME MORE ACTIVE/BETTER ORGANIZED
ON FRIDAY...WITH RAINFALL AMOUNTS OF 25-50MM/DAY AND MAXIMA OF
75-150MM. THROUGH SUNDAY THIS WILL DECREASE TO 10-15MM/DAY AND
MAXIMA OF 20-40MM. OVER SOUTHERN VENEZUELA INITIALLY EXPECTING
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM...INCREASING
TO 15-20MM/DAY AND MAXIMA OF 35-70MM ON SATURDAY. OVER THE
NORTHERN GUIANAS EXPECTING RAINFALL ACCUMULATION OF 00-05MM AND
MAXIMA OF 10MM THROUGH FRIDAY MORNING...GRADUALLY INCREASING TO
10-15MM/DAY AND MAXIMA OF 20-35MM DURING THE WEEKEND. OTHER
CONVECTION TO THE SOUTH IS TO CLUSTER ALONG THE NEAR EQUATORIAL
TROUGH...SUSTAINING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM.

CONSISTENT WITH PREVIOUS FORECASTS...A MID/UPPER LEVEL HIGH OFF
THE SOUTHEAST COAST OF THE USA IS TO GRADUALLY BUILD A RIDGE
ACROSS THE WESTERN ATLANTIC THROUGH FRIDAY EVENING...WITH AXIS TO
THEN HOLD THROUGHOUT THE WEEKEND/EARLY NEXT WEEK. UNDER INFLUENCE
OF THE BUILDING RIDGE...A TUTT WILL PULL ACROSS THE BAHAMAS TO
JUST NORTH OF PUERTO RICO/HISPANIOLA-LEEWARD ISLES ON
FRIDAY...WHERE IT IS TO REMAIN THROUGH EARLY NEXT WEEK. AS IT
MEANDERS TO THE NORTH OF PUERTO RICO...A JET MAXIMA ROUNDING THE
BASE OF THE TROUGH WILL REPOSITION JUST NORTH OF THE ISLAND LATER
ON FRIDAY-EARLY SATURDAY MORNING. THIS IS TO THEN FAVOR AN UPPER
DIVERGENT PATTERN ACROSS THE NORTHEAST CARIBBEAN. AT 500 HPA THE
TROUGH ALOFT WILL SUSTAIN AN ILL ORGANIZED LOW THAT MEANDERS JUST
NORTH OF PUERTO RICO ON FRIDAY-SATURDAY...MOVING NORTH OF THE
LEEWARD ISLES ON SUNDAY. THIS IS TO SUSTAIN WEAK POSITIVE
VORTICITY ADVECTION ALONG THE NORTH COAST OF PUERTO RICO THROUGH
MIDDAY ON SATURDAY...AND THE VI/NORTHERN LEEWARD ISLES LATER ON
SATURDAY THROUGH MONDAY MORNING. AT LOW LEVELS...A HIGH TO THE
EAST-NORTHEAST OF BERMUDA WILL ANCHOR A RIDGE ACROSS THE WESTERN
ATLANTIC. THE RIDGE IS TO BUILD WEST ACROSS THE FLORIDA
PENINSULA/CUBA LATER TODAY...INTO THE CENTRAL GULF EARLY ON
FRIDAY. ACROSS THE BASIN THIS WILL FAVOR A TIGHT GRADIENT AND
BRISK EASTERLY WINDS...WITH BOUNDARY LAYER WINDS FORECAST TO PEAK
AT 15-25KT. THIS WOULD LIKELY FAVOR GENERATION OF STREAMERS ACROSS
THE ISLAND CHAIN INTO THE EASTERN CARIBBEAN. FURTHERMORE...THE
EASTERLIES ARE ALSO CONVERGING OVER THE FRENCH ISLES...WITH PWAT
ANALYSIS SHOWING MOISTURE CONTENT OF 40-50MM CLUSTERING OVER THE
ISLANDS. AS THE TUTT SETTLES TO THE NORTH THIS WILL THEN DRAW THE
MOISTURE NORTH TO THE LEEWARD ISLES/NORTHEAST CARIBBEAN EARLY ON
FRIDAY...WHERE IT IS TO GENERALLY PERSIST THROUGH THE WEEKEND.
EARLY IN THE CYCLE THIS WILL FEED SCATTERED CONVECTION OVER THE
FRENCH ISLES TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA
OF 20-30MM. AS IT SHIFTS NORTH ACROSS THE LEEWARD ISLES ON
FRIDAY-SATURDAY THIS INCREASES TO 15-20MM/DAY AND MAXIMA OF
25-50MM. OVER HAITI-CUBA-SOUTHEAST BAHAMAS THE TUTT IS TO SUSTAIN
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM EARLY IN THE
CYCLE. BUT AS IT PULLS AWAY IT DECREASES TO 00-05MM/DAY AND MAXIMA
OF 10MM ON FRIDAY. OVER THE DOMINICAN REPUBLIC-WESTERN PUERTO RICO
INITIALLY EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM. ON FRIDAY-SATURDAY THIS WILL INCREASE TO 15-20MM/DAY AND
MAXIMA OF 35-70MM. ON SATURDAY FOCUS OF THE HEAVY CONVECTION
SHIFTS TO EASTERN PUERTO RICO-VIRGIN ISLES-NORTHERN LEEWARD
ISLANDS... WHERE ENVIRONMENTAL CONDITIONS WILL BECOME HIGHLY
FAVORABLE AND CONDUCIVE TO GENERATION OF AN MCS DURING THE MORNING
HOURS...WITH RAINFALL AMOUNTS OF 20-30MM/DAY AND MAXIMA OF
50-100MM. AS MJO PATTERN BECOMES MORE FAVORABLE...AS SOME OF THE
CLIMO MODELS SUGGEST...THERE IS AN ELEVATED RISK OF HIGHER
RAINFALL AMOUNTS LATER DURING THE WEEKEND/EARLY NEXT WEEK.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24     36     48     60     72     84     96       TYPE
23W      27W    31W    34W    37W    41W    45W    50W       TW
44W      47W    51W    54W    57W    59W    61W    64W       TW
55W      57W    60W    63W    66W    68W    70W    71W       TW
69W      71W    73W    75W    77W    79W    DISSIPATES       TW

A TROPICAL WAVE IS INITIALIZED ALONG 23W AND SOUTH OF 05N. THIS
NOW APPEARS SOMEWHAT BETTER ORGANIZED AND IT IS NOW FORECAST TO
PERSIST THROUGH SUNDAY...MEANWHILE FAVORING SCATTERED CONVECTION
ALONG THE ATLANTIC ITCZ.

A TROPICAL WAVE IS INITIALIZED ALONG 44W AND SOUTH OF 06N. PER THE
PWAT ANALYSIS...DEEP MOISTURE ACCOMPANIES THIS FEATURE. THE WAVE
ENTERS FRENCH GUIANA EARLY ON FRIDAY MORNING...WHERE IT IS TO
SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-45MM.
SIMILAR AMOUNTS ARE FORECAST ACROSS SURINAME-GUYANA LATER ON
FRIDAY/EARLY SATURDAY MORNING. LATER ON SATURDAY CONVECTION IS TO
SPREAD ACROSS NORTHERN GUYANA TO NORTHEAST VENEZUELA TO THE
SOUTHERN WINDWARD ISLES/TRINIDAD AND TOBAGO...WHERE IT IS TO FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER
CENTRAL-SOUTHERN VENEZUELA IT IS TO THEN TRIGGER RAINFALL AMOUNTS
OF 10-15MM/DAY AND MAXIMA OF 20-30MM ON SUNDAY.

A TROPICAL WAVE IS INITIALIZED ALONG 55W AND SOUTH OF 06N. THIS
MOVES ACROSS GUYANA TO SOUTHERN VENEZUELA EARLY ON FRIDAY
MORNING...WHERE IN INTERACTION WITH THE NET IT IS TO TRIGGER
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. LATER ON
SATURDAY IT PULLS TO ACROSS EASTERN COLOMBIA...WHERE IT WILL
SUSTAIN RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 35-70MM. ON
SUNDAY IT DECREASES TO 10-15MM/DAY AND MAXIMA OF 20-40MM AS IT
MOVES ACROSS SOUTHERN COLOMBIA.

A TROPICAL WAVE IS INITIALIZED ALONG 69W AND SOUTH OF 06N. THIS
TENDS TO WEAKEN AS IT CROSSES THE ANDES LATER DURING THE WEEKEND.
MEANWHILE...ACROSS SOUTHERN COLOMBIA IT IS TO SUSTAIN RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM.

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




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