Prognostic Meteorological Discussion
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FXCA20 KWBC 231828
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
228 PM EDT WED MAY 23 2018

TROPICAL DISCUSSION FROM MAY 23/12 UTC: A 500 HPA HIGH OVER
SOUTHWEST MEXICO ANCHORS A RIDGE THAT IS FORECAST TO BUILD NORTH
ACROSS MEXICO TO THE SOUTHWESTERN USA DURING THE NEXT FEW DAYS. IN
A SINUSOIDAL PATTERN...AS THE RIDGE TO THE WEST BUILDS...A TROUGH
TO THE EAST IS TO AMPLIFY. EARLY IN THE CYCLE THE NEGATIVELY
TILTED TROUGH WILL EXTEND TO THE SOUTHEAST FROM THE NORTHWEST
GULF...ACROSS THE YUCATAN TO NORTHERN CENTRAL AMERICA. AS IT
DEEPENS...THIS IS TO THEN STEER A SHORT WAVE PERTURBATION NORTH
ACROSS THE NORTHWEST CARIBBEAN/WESTERN CUBA LATER TODAY. ON
THURSDAY THIS IS TO THEN MERGE WITH THE DEEPENING TROUGH OVER THE
GULF OF MEXICO. THE NEGATIVELY TILTED TROUGH IS TO THEN HOLD
THROUGH SATURDAY MORNING. AT LOW LEVELS...THE TROUGH ALOFT
SUSTAINS THE NORTHWARD AMPLIFICATION OF A TROUGH ALONG 88W TO THE
EASTERN GULF OF MEXICO...WITH AXIS ANCHORING ON AN ILL ORGANIZED
LOW OFF THE COAST OF QUINTANA ROO/YUCATAN. MODELS CONTINUE TO SHOW
THIS LOW SLOWLY BECOMING BETTER ORGANIZED AS IT LIFTS NORTH ACROSS
THE YUCATAN CHANEL LATER IN THE WEEK. THE NHC CONTINUES TO MONITOR
THIS FEATURE FOR POSSIBILITY OF A TROPICAL OR SUBTROPICAL CYCLONE
FORMATION.

MEANWHILE...THIS WILL ENHANCE LOW LEVEL MOISTURE CONVERGENCE
ACROSS THE NORTHWEST CARIBBEAN ISLES. OVER THE CAYMAN ISLANDS
EXPECTING RAINFALL AMOUNTS OF 20-30MM/DAY AND MAXIMA OF 40-80MM
THROUGH THURSDAY MORNING. ON THURSDAY-FRIDAY EXPECT ACCUMULATION
OF 15-20MM/DAY AND MAXIMA OF 25-50MM...WHILE ON FRIDAY EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. OVER WESTERN
CUBA HEAVY RAINS ARE TO PERSIST THROUGH THE END OF THE WEEK...WITH
RAINFALL AMOUNTS OF 50-100MM/DAY AND MAXIMA OF 150-250MM/DAY. IN
THIS AREA...CONFIDENCE IN THE FORECAST IS HIGH THROUGH FRIDAY.
LESSER AMOUNTS ARE EXPECTED OVER JAMAICA...WITH ACCUMULATION OF
05-10MM/DAY AND MAXIMA OF 15MM/DAY. THE MEANDERING TROUGH IS TO
ALSO ENHANCE MOISTURE CONVERGENCE ACROSS THE YUCATAN
PENINSULA-NORTHERN BELIZE. INITIALLY EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-45MM. ON THURSDAY THIS INCREASES TO
20-30MM/DAY AND MAXIMA OF 40-80MM...WITH POTENTIAL FOR LOCALLY
HIGHER AMOUNTS. ON FRIDAY-SATURDAY THIS IS TO THEN FAVOR RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-45MM/DAY.

ALSO...UNDER INFLUENCE OF THE DEEP LAYER TROUGH OVER THE WESTERN
CARIBBEAN...THE EASTERN PACIFIC ITCZ REMAINS NORTH OF ITS
CLIMATOLOGICAL POSITION...WITH AXIS EXTENDING ACROSS CENTRAL
AMERICA TO THE CENTRAL CARIBBEAN. LATER ON THURSDAY/EARLY ON
FRIDAY MORNING....AS THE CYCLONIC CIRCULATION OVER THE NORTHWEST
CARIBBEAN BECOMES BETTER ORGANIZED...A LONG FETCH WEST-SOUTHWEST
FLOW IS TO ESTABLISH ACROSS THE EASTERN PACIFIC TO WESTERN
NICARAGUA-SOUTHEAST HONDURAS/EL SALVADOR. THIS WILL ENHANCE
MOISTURE TRANSPORT AND CONVERGENCE ALONG THE CONTINENTAL DIVIDE...
SUSTAINING THE GRADUAL INTENSIFICATION OF THE DIURNAL CONVECTION.
EARLY IN THE CYCLE EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-45MM/DAY. ON THURSDAY-FRIDAY...AS THE WINDS SHIFT TO
THE WEST...THIS INCREASES TO 20-30MM/DAY AND MAXIMA OF
50-100MM/DAY. OVER SOUTHERN NICARAGUA/COSTA RICA...ALONG THE
ITCZ...EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM. ON THURSDAY-FRIDAY THIS INCREASES TO 15-20MM/DAY AND
MAXIMA OF 30-60MM...WHILE ON FRIDAY AND SATURDAY THE MAXIMA
DECREASES TO 20-40MM. ACROSS EASTERN NICARAGUA/NORTHEAST HONDURAS
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM/DAY. OVER NORTHERN COLOMBIA/NORTHWEST VENEZUELA EXPECTING
SCATTERED CONVECTION WITH ACCUMULATION OF 15-20MM/DAY AND MAXIMA
OF 35-70MM. THROUGH THURSDAY THIS WILL DECREASE TO 10-15MM/DAY AND
MAXIMA OF 20-35MM/DAY. ON THE ANDEAN REGION/WESTERN COASTAL PLAINS
OF COLOMBIA INITIALLY EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 15-20MM. ON THURSDAY...UNDER INFLUENCE OF A TROPICAL
WAVE...THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-35MM/DAY. ON
THE PIEDEMONTE LLANERO/AMAZONIA IN EASTERN COLOMBIA-AMAZONIA IN
SOUTHERN VENEZUELA EXPECTING RAINFALL AMOUNTS OF 15-20MM/DAY AND
MAXIMA OF 35-70MM...WHILE ON THURSDAY-SATURDAY EXPECTING
ADDITIONAL RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF
30-60MM/DAY.

MID/UPPER LEVEL RIDGE REMAINS OVER THE BAHAMAS/SOUTHWESTERN
ATLANTIC. A TUTT TO THE EAST EXTENDS FROM A CLOSED LOW AT 22N 55W
TO THE NORTHEAST CARIBBEAN ISLES. UNDER PRESSURE FROM POLAR TROUGH
EXITING THE NORTHEASTERN USA EARLY IN THE CYCLE...THE MID LEVEL
RIDGE OVER THE WESTERN ATLANTIC IS RAPIDLY FLATTEN. IN
RESPONSE...THE TUTT TO THE EAST IS TO THEN WEAKEN WHILE RAPIDLY
LIFTING TO THE NORTH-NORTHEAST. LATER INTO THE WEEKEND THE RIDGE
BOUNCES BACK...STRENGTHENING ITS FOOTHOLD ACROSS THE WESTERN
ATLANTIC/EASTERN CARIBBEAN. THIS WILL HELP SUSTAIN AN ELEVATED
TRADE WINDS CAP ACROSS THE EASTERN CARIBBEAN...WITH MOISTURE
CAPPING AROUND 650/700 HPA. AT LOW LEVELS...BROAD CELL OF THE
SUBTROPICAL RIDGE REMAINS DOMINANT FEATURE OVER THE
ATLANTIC-CARIBBEAN BASIN. POLAR FRONT ENTERING THE WESTERN
ATLANTIC WILL PRESS AGAINST THIS RIDGE. THIS WILL FAVOR THE
EROSION OF LOW LEVEL RIDGE PATTERN FROM THE WEST. AS A
RESULT...THE LOW LEVEL WINDS WILL VEER TO THE EAST-SOUTHEAST LATER
TODAY. THIS WILL ENHANCE MOISTURE TRANSPORT/CONVERGENCE ACROSS THE
NORTHEAST CARIBBEAN...WITH PWAT CONTENT OF 20-30MM EARLY IN THE
CYCLE TO GRADUALLY INCREASE TO 35-40MM ON THURSDAY-FRIDAY. THE
INFLOW OF MOISTURE WILL THEN HELP SUSTAIN AN INCREASE IN DIURNAL
CONVECTION. OVER PUERTO RICO-HISPANIOLA SHALLOW DIURNAL CONVECTION
IS TO RESULT IN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM. ON THURSDAY-FRIDAY ACTIVITY ACROSS PUERTO RICO INCREASES
TO 10-15MM/DAY AND MAXIMA OF 20-45MM/DAY. THIS WILL GRADUALLY
BUILD WEST ACROSS THE DOMINICAN REPUBLIC ON FRIDAY TO SATURDAY.
OVER THE VIRGIN ISLES AND THE LESSER ANTILLES ISLES EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM/DAY THROUGH
THURSDAY MORNING...WITH LESSER AMOUNTS LATER IN THE WEEK.

SOUTH OF THE TUTT...CELL OF THE SUBEQUATORIAL RIDGE DOMINATES THE
UPPER LEVELS OVER THE TROPICAL ATLANTIC-NORTHERN GUIANAS...WITH
AXIS ORIGINATING AT 250 HPA ON A CLOSED HIGH NEAR 10N 37W. THIS IS
VENTING DIURNAL CONVECTION...WITH ACTIVITY BUILDING NORTH ALONG
THE ATLANTIC ITCZ/NEAR EQUATORIAL TROUGH. UNDER INFLUENCE OF A
TROPICAL WAVE ACTIVITY OVER THE GUIANAS IS TO BECOME MORE
ACTIVE/BETTER ORGANIZED. ACROSS FRENCH GUIANA-SURINAME EXPECTING
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM...DECREASING
TO 10-15MM/DAY AND MAXIMA OF 20-30MM ON THURSDAY-FRIDAY...WHILE ON
FRIDAY EXPECTING ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF
15-20MM. ACROSS GUYANA TO EASTERN VENEZUELA THIS WILL INCREASE
THROUGH FRIDAY TO 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
44W     47W   49W   52W   55W   57W   60W   62W        TW
16N
72W     74W   76W   78W   80W   82W   DISSIPATES       TW
16N
88W     88W   88W   88W   88W   87W   87W   87W     TUTT INDCD
29N

A TROPICAL WAVE ALONG 44W AND SOUTH OF 14N ENTERS FRENCH GUIANA BY
MIDDAY ON THURSDAY...TO TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-30MM. THIS IS TO QUICKLY SPREAD ACROSS SURINAME
DURING THE DAY. THROUGH FRIDAY...AS IT BUILDS ACROSS GUYANA...
THIS INCREASES TO 15-20MM/DAY AND MAXIMA OF 30-60MM. ON SATURDAY
THIS IS TO TRIGGER SCATTERED CONVECTION ACROSS EASTERN
VENEZUELA...WITH ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF
30-60MM. OVER THE FRENCH AND WINDWARD ISLES TO TRINIDAD/TOBAGO AND
THE GRENADINES EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM.

A TROPICAL WAVE ALONG 72W AND SOUTH OF 16N IS TO DISSIPATE ON
SATURDAY AS IT INTERACTS WITH TUTT INDUCED PERTURBATION OVER
CENTRAL AMERICA/WESTERN CARIBBEAN. MEANWHILE...ACROSS WESTERN
VENEZUELA/EASTERN COLOMBIA THIS IS TO SUSTAIN RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 35-70MM. OVER NORTHERN COLOMBIA TO
EASTERN PANAMA EXPECTING ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF
20-35MM ON THURSDAY TO FRIDAY...WHILE ACROSS COSTA RICA THIS IS TO
TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM ON
FRIDAY TO SATURDAY. MOST INTENSE TO CLUSTER ALONG THE CONTINENTAL
DIVIDE.

THE TUTT OVER THE GULF/WESTERN CARIBBEAN SUSTAINS AN INDUCED
TROUGH IN THE EASTERLY TRADES WITH AXIS ALONG 88W TO 29N. NHC IS
MONITORING THIS FEATURE FOR POSSIBILITY OF TROPICAL/SUBTROPICAL
CYCLONE FORMATION.

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

$$





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