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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1841Z May 15, 2018)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
241 PM EDT TUE MAY 15 2018

TROPICAL DISCUSSION FROM MAY 15/12 UTC: BROAD MID/UPPER LEVEL
RIDGE CONTINUES TO DOMINATE THE FLOW ACROSS WESTERN PORTIONS OF
THE DOMAIN. THE RIDGE EXTENDS NORTH ACROSS MEXICO TO THE SOUTHWEST
USA WHILE ANCHORING ON A CLOSED HIGH TO THE WEST OF
COLIMA/NAYARIT. THIS IS TO GENERALLY PERSIST DURING THE NEXT FEW
DAYS...MEANWHILE FAVORING A MID LEVEL SUBSIDENCE INVERSION. THIS
WILL BE STRONG ENOUGH TO DELAY THE ONSET OF DEEP CONVECTION TO THE
LATE AFTERNOON HOURS. ON THE CENTRAL STATES OF MEXICO...TO AFFECT
PORTIONS OF VERACRUZ-OAXACA-MEXICO/MEXICO DF-GUERRERO EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM/DAY. OTHER
CONVECTION IS TO CLUSTER OVER SOUTHWEST MEXICO ON
WEDNESDAY-THURSDAY...TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM.

AS THE MID/UPPER LEVEL RIDGE HOLDS TO THE WEST...IT IS TO STEER
SHORT WAVE PERTURBATIONS ACROSS THE LOWER MISSISSIPPI VALLEY TO
THE GULF OF MEXICO. THESE ARE TO THEN FEED INTO A MEANDERING
TROUGH TO THE EAST. THE TROUGH EXTENDS SOUTH FROM A CLOSED LOW OFF
THE GULF COAST OF FLORIDA TO THE WESTERN CARIBBEAN/NORTHERN
CENTRAL AMERICA. THROUGH THURSDAY THE TROUGH IS FORECAST TO
RETROGRESS ACROSS THE YUCATAN TO GUATEMALA/WESTERN HONDURAS. EARLY
IN THE PERIOD THIS IS TO FAVOR DEEP LAYER INSTABILITY ACROSS
WESTERN/CENTRAL CUBA AND THE CENTRAL/NORTHWEST BAHAMAS. AS THE
TROUGH RETROGRESSES TO THE YUCATAN...AIR MASS ACROSS THE
BAHAMAS-CUBA WILL START TO STABILIZE...WHILE OVER
BELIZE/YUCATAN-WESTERN CARIBBEAN IT IS TO BECOME MORE UNSTABLE.
MEANWHILE...OVER WESTERN CUBA AND THE BAHAMAS ENVIRONMENTAL
CONDITIONS ARE TO REMAIN FAVORABLE FOR GENERATION OF MESOSCALE
CONVECTIVE SYSTEMS AND POTENTIALLY SEVERE CONVECTION. DURING THE
SHORT RANGE PERIOD FORECASTED LIFTED INDEX WILL PEAK BETWEEN -6
AND -9. IN THIS AREA EXPECTING RAINFALL AMOUNTS OF 20-35MM/DAY AND
MAXIMA OF 50-100MM THROUGH WEDNESDAY MORNING. OVER THE NORTHWEST
BAHAMAS...ON WEDNESDAY-TO-THURSDAY...EXPECTING ACCUMULATION OF
15-20MM/DAY AND MAXIMA OF 25-50MM. ON THURSDAY TO FRIDAY THIS
DECREASES TO 10-15MM/DAY AND MAXIMA OF 20-40MM. OVER WESTERN
CUBA...ON WEDNESDAY-FRIDAY EXPECTING ADDITIONAL RAINFALL AMOUNTS
OF 15-20MM/DAY AND MAXIMA OF 30-60MM...WITH LOCALLY HIGHER AMOUNTS
HIGHLY PROBABLE. ACROSS THE CAYMAN ISLES AND JAMAICA...AS A SHORT
WAVE VORTEX ROUNDS THE BASE OF THE TROUGH ON TUESDAY...EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM IN SCATTERED
DEEP CONVECTION. A SECOND ROUND OF CONVECTION IS EXPECTED ON
THURSDAY-FRIDAY TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA 15-25MM.

AS IT MEANDERS OVER THE WESTERN CARIBBEAN...THE DEEP MID/UPPER
LEVEL TROUGH IS TO ALSO ENHANCE CONVECTION ACROSS THE YUCATAN
PENINSULA TO NORTHERN CENTRAL AMERICA. OVER YUCATAN-QUINTANA ROO
AND BELIZE INITIALLY EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-25MM/DAY. THROUGH THURSDAY THIS WILL INCREASE TO
15-20MM/DAY AND MAXIMA OF 30-60MM...WITH RISK OF SEVERE WEATHER.
HIGHER RAINFALL AMOUNTS ARE EXPECTED BETWEEN NORTHWEST
NICARAGUA-SOUTHEAST HONDURAS AND EL SALVADOR...WHERE THE DEEP MID
LEVEL TROUGH IS TO FAVOR A MOIST WEST-SOUTHWESTERLY FLOW. IN THIS
AREA INITIALLY EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-45MM. THROUGH THURSDAY THIS WILL INCREASE TO
20-30MM/DAY AND MAXIMA OF 40-80MM. THE SOUTHWESTERLY FLOW IS TO
ALSO AID IN THE NORTHWARD MODULATION OF THE EASTERN PACIFIC ITCZ
ACROSS SOUTHERN NICARAGUA/COSTA RICA TO THE SOUTHERN
CARIBBEAN-NORTHERN COLOMBIA. OVER PANAMA-COSTA RICA INITIALLY
EXPECTING RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM.
BUT AS THE ITCZ MEANDERS NORTH OF ITS CLIMATOLOGICAL POSITION ON
WEDNESDAY THIS WILL DECREASE TO 05-10MM/DAY AND MAXIMA OF
15-25MM/DAY. SIMULTANEOUSLY...CONVECTION ACROSS SOUTHERN AND
EASTERN NICARAGUA IS TO SURGE...INCREASING FROM 05-10MM/DAY AND
MAXIMA OF 15-25MM EARLY IN THE CYCLE TO 15-20MM/DAY AND MAXIMA OF
25-50MM ON WEDNESDAY-FRIDAY. OVER COLOMBIA MOST ACTIVE CONVECTION
IS EXPECTED TO THE NORTH...WITH RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-40MM. ON THE ANDEAN REGION AND EJE CAFETERO TO
THE SOUTH EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-25MM.

A MID/UPPER LEVEL RIDGE OVER THE EASTERN CARIBBEAN/WESTERN
ATLANTIC SEPARATES THE TROUGH OVER THE GULF OF MEXICO FROM A TUTT
OVER THE CENTRAL ATLANTIC. THE RIDGE FAVORS A TRADE WINDS CAP
ACROSS THE NORTHEAST CARIBBEAN ISLES. IN BRISK EASTERLY
TRADES...CLUSTERS OF SHALLOW CLOUD COVER ARE STREAMING UNDER THIS
AXIS INTO THE NORTHEAST CARIBBEAN. CONSISTENT WITH THE PREVIOUS
FORECAST...THE MID LEVEL HIGH IS FORECAST TO SLOWLY LIFT NORTH.
THIS WILL THEN ALLOW THE TUTT TO RETROGRESS ACROSS THE LEEWARD
ISLES TO THE NORTHEAST CARIBBEAN BY MIDMORNING ON
WEDNESDAY...WHERE IT IS TO REMAIN THROUGH THE END OF THE WEEK. AS
IT MEANDERS OVER THE NORTHEAST CARIBBEAN...THE TROUGH IS TO THEN
FOCUS ITS SHORT WAVE ENERGY ACROSS THE LEEWARD-VIRGIN ISLES-PUERTO
RICO...WITH WEAK PVA EXPECTED FROM WEDNESDAY THROUGH AT LEAST
SATURDAY. AT LOW LEVELS...BROAD CELL OF THE SUBTROPICAL RIDGE IS
TO DOMINATE THE FLOW ACROSS THE BASIN...TO CONTINUE FAVORING BRISK
EASTERLY TRADES. EARLY IN THE CYCLE THE 850 HPA WINDS ARE TO PEAK
AT 15-20KT...AND THROUGH THE END OF THE WORKWEEK THESE INCREASE TO
20-25KT. THIS IS TO CONTINUE FAVORING ADVECTION OF IRREGULARLY
SPACED CLOUD CLUSTERS/PLUMES OF SHALLOW MOISTURE ACROSS THE
NORTHEAST CARIBBEAN. PWAT CONTENT WITH THESE IS TO PEAK AT
30-35MM...HIGH ENOUGH TO FAVOR PERIODS OF MODERATE/LOCALLY HEAVY
RAINFALL AMOUNTS. OVER THE FRENCH/LEEWARD ISLES EXPECTING RAINFALL
AMOUNTS OF 05MM/DAY AND MAXIMA OF 15MM...MOST ACTIVE EARLY IN THE
CYCLE. OVER PUERTO RICO ACTIVITY INCREASES ON WEDNESDAY...WHEN IT
IS TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM. OVER THE DOMINICAN REPUBLIC EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40MM EARLY IN THE CYCLE...WHILE OVER
HAITI THE MAXIMA PEAKS AT 20-35MM. OVER THE ISLAND THIS DECREASES
TO 05-10MM/DAY AND MAXIMA OF 15-20MM ON WEDNESDAY-FRIDAY.

TUTT OVER THE CENTRAL ATLANTIC IS TO ALSO PRESS AGAINST A CELL OF
THE SUBEQUATORIAL RIDGE TO THE SOUTH. THIS WILL LEAD TO EROSION OF
UPPER LEVEL RIDGE PATTERN OVER THE GUIANAS...WHILE A WEAK CELL IS
TO REMAIN ACROSS VENEZUELA/COLOMBIA. ACROSS VENEZUELA-COLOMBIA
THIS IS TO VENT DEEP CONVECTION ALONG THE NEAR EQUATORIAL TROUGH.
OVER SOUTHEAST COLOMBIA-AMAZONIA IN SOUTHERN VENEZUELA EXPECTING
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM. THROUGH
WEDNESDAY THIS DECREASES TO 10-15MM/DAY AND MAXIMA OF 20-35MM.
ACROSS THE GUIANAS EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-25MM. ON THURSDAY THIS INCREASES TO 10-15MM/DAY AND
MAXIMA OF 20-40MM.

TROPICAL/EASTERLY WAVES/TRADE WIND SURGES INITIALIZED AT 12UTC:
INITIAL 24    36    48    60    72    84    96        TYPE      
SOF
34W     36W   38W   40W   42W   44W   46W   49W        TW       
08N
65W     68W   71W   73W   75W   78W   80W   82W        EW       
10N
82W     83W   84W   85W   86W   DISSIPATES             EW       
15N

TROPICAL WAVE ALONG 34W AND SOUTH OF 08N IS TO CONFINE TO THE
ATLANTIC ITCZ DURING THE NEXT FOUR DAYS.

AN EASTERLY WAVE ALONG 65W AND SOUTH OF 10N IS TO ENHANCE DIURNAL
CONVECTION ACROSS VENEZUELA...TO FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40MM. LATER TODAY/EARLY ON
WEDNESDAY...AS IT MOVES TO WESTERN VENEZUELA/EASTERN
COLOMBIA...THIS IS TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-35MM. THIS IS TO THEN ENHANCE CONVECTION ACROSS
NORTHERN COLOMBIA ON THURSDAY...TO FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40MM....WHILE OVER WESTERN
COLOMBIA/PANAMA EXPECTING ACCUMULATION OF 05-10MM/DAY AND MAXIMA
OF 15-25MM.

AN EASTERLY WAVE ALONG 82W AND SOUTH OF 15N IS TO ENHANCE ITCZ
RELATED CONVECTION ACROSS WESTERN PANAMA/COSTA RICA EARLY IN THE
PERIOD...WITH RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF
30-60MM. OVER SOUTHERN/WESTERN NICARAGUA-EL SALVADOR/SOUTHERN
HONDURAS THIS IS TO THEN SUSTAIN RAINFALL AMOUNTS OF 20-30MM/DAY
AND MAXIMA OF 35-70MM.

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