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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1856Z Aug 14, 2018)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT TUE AUG 14 2018

TROPICAL DISCUSSION FROM AUG 14/12 UTC: UPPER RIDGE ORIGINALLY
CENTERS ON A HIGH OVER THE NORTHEASTERN GULF OF MEXICO AND EXTENDS
AN AXIS INTO NORTHWESTERN MEXICO. THE RIDGE IS FORECAST TO
RELOCATE THROUGH THE CYCLE...TO FORM A HIGH OVER EXTREME
NORTHWESTERN MEXICO BY THURSDAY. UPPER LOWS ARE PROPAGATING
WESTWARD ALONG THE SOUTHERN FRINGES OF THE RIDGE. ONE IS EXITING
INTO THE PACIFIC TO CENTER OVER COLIMA ON TUESDAY EVENING...WHILE
ANOTHER APPROACHES FROM THE CARIBBEAN TO CENTER OVER YUCATAN
PENINSULA ON WEDNESDAY....AND OVER THE SOUTHERN GULF OF MEXICO BY
THURSDAY. INTERACTIONS BETWEEN THE UPPER RIDGE AND LOWS WILL
PROVIDE VENTILATION TO SUSTAIN DAILY CONVECTION ALONG SOUTHERN AND
WESTERN MEXICO...WHERE CONVECTIVE INSTABILITY REMAINS SEASONALLY
HIGH. THROUGH EARLY WEDNESDAY...LARGEST ACCUMULATIONS WILL CLUSTER
BETWEEN CHIAPAS AND GUERRERO WHERE EXPECTING 15-20MM/DAY AND
MAXIMA OF 25-50MM/DAY. THIS WILL DECREASE TO 10-15MM/DAY AND
MAXIMA OF 20-30MM AFTER. DIURNAL CONVECTION IS ALSO EXPECTED IN
THE SIERRA MADRE OCCIDENTAL...WHERE EXPECTING 10-15MM/DAY AND
ISOLATED MAXIMA OF 20-30MM ON TUESDAY...DECREASING TO 05-10MM/DAY
AND MAXIMA OF 15-20MM BY THURSDAY. ISOLATED DIURNAL THUNDERSTORMS
IN THE YUCATAN PENINSULA WILL SUSTAIN MAXIMA OF 15MM.

TO THE EAST...WHILE MID-UPPER RIDGE PATTERN CONTINUES EXTENDING
FROM THE NORTH ATLANTIC NEAR 28N-35N INTO THE NORTHERN
BAHAMAS...THE CORRIDOR SUITABLE FOR RETROGRESSING UPPER LOWS HAS
ESTABLISHED AT LATITUDES OF 16N-21N. IN THIS CORRIDOR...A TUTT LOW
CENTERS JUST TO THE EAST OF THE LEEWARD ISLANDS. THIS TUTT IS
FORECAST TO MEANDER WESTWARD TO CENTER OVER PUERTO RICO BY
WEDNESDAY EVENING...OVER HISPANIOLA BY THURSDAY EVENING...AND OVER
THE SOUTHEAST BAHAMAS/SOUTHEASTERN CUBA BY FRIDAY EVENING. AT
LOW-LEVELS...A SURGE IN CONVECTION IS RAPIDLY TRAILING WESTWARD IN
ASSOCIATION WITH AN EASTERLY WAVE (SEE BELOW) AND CONVERGENCE
AHEAD OF FAST 15-20KT TRADES NORTH OF THE GREATER ANTILLES. THIS
SYSTEM WILL INITIALLY STIMULATE CONVECTION IN SOUTHEASTERN CUBA
AND WESTERN JAMAICA ON TUESDAY TO PRODUCE 05-10MM/DAY AND MAXIMA
OF 15-20MM. BY WEDNESDAY IT WILL LEAD TO A PEAK IN CONVECTION IN
CENTRAL AND WESTERN CUBA WHERE IT WILL SUSTAIN 10-15MM/DAY AND
MAXIMA OF 20-35MM. IN WESTERN JAMAICA AND THE CAYMAN ISLANDS
EXPECTING ISOLATED THUNDERSTORMS. ACTIVITY WILL DECREASE
THEREAFTER. IN THE CENTRAL AND NORTHERN BAHAMAS...EXPECTING FAIR
CONDITIONS THROUGH THURSDAY UNDER THE INFLUENCE OF THE BERMUDA
HIGH AND DRY AIR MASS ABOVE THE TRADE WIND CAP. THIS WILL BE
FOLLOWED BY A WETTER PATTERN INTO THE WEEKEND IN ASSOCIATION WITH
DESTABILIZATION IN UPSTREAM CONVECTION PRODUCED BY THE
RETROGRESSING TUTT.

TO THE EAST...THE RETROGRESSING TUTT WILL ALSO STIMULATE
CONVECTION IN HISPANIOLA...PUERTO RICO AND THE NORTHEASTERN
CARIBBEAN ISLES. INITIALLY... ACTIVITY WILL BE GENERALLY ISOLATED
DUE TO THE PRESENCE OF A DRY AIR MASS ABOVE THE TRADE WIND CAP. A
MORE SIGNIFICANT INCREASE IN PRECIPITATION IS EXPECTED BY
WEDNESDAY-THURSDAY IN THE LEEWARD ISLANDS/FRENCH ANTILLES...AND BY
THURSDAY THROUGH SATURDAY IN AREAS TO THE WEST IN ASSOCIATION WITH
MOIST PLUME ARRIVING FROM THE TROPICAL ATLANTIC. THE MOIST SURGE
WILL BE FURTHER REINFORCED BY TROPICAL WAVE (SEE BELOW). IN TERMS
OF ACCUMULATIONS...EXPECTING ISOLATED AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM IN HISPANIOLA ON TUESDAY. BY
WEDNESDAY...EXPECTING A DECREASE IN HISPANIOLA...WHILE ACTIVITY
INCREASES ACROSS THE CENTRAL/NORTHEASTERN LESSER ANTILLES INTO
PUERTO RICO TO 05-10MM/DAY AND MAXIMA OF 15MM. BY
THURSDAY-FRIDAY...EXPECTING AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-25MM IN PUERTO RICO AND HISPANIOLA...WHILE EXPECTING MAXIMA OF
15-20MM IN THE NORTHERN LESSER ANTILLES.

CONVECTION IN THE SOUTHERN CARIBBEAN...NORTHERN SOUTH AMERICA AND
CENTRAL AMERICA WILL BE LARGELY SENSITIVE TO THE INFLUENCE OF
TROPICAL AND EASTERLY WAVES (SEE BELOW). AT UPPER LEVELS...RIDGE
IN THE SOUTHERN CARIBBEAN WILL PLAY A ROLE IN ENHANCING UPPER
DIVERGENCE ALONG ITS SOUTHERN PERIPHERY ESPECIALLY ACROSS NORTHERN
COLOMBIA/NORTHWEST VENEZUELA ON TUESDAY...SOUTHERN CARIBBEAN...AND
SOUTHWESTERN CARIBBEAN/NICARAGUA/HONDURAS ON THURSDAY. THIS WILL
SUSTAIN MODERATE RAINFALL ACCUMULATIONS (AMOUNTS DESCRIBED ON THE
WAVE SECTION).

TROPICAL/EASTERLY WAVES/TRADE WIND SURGES FROM 00 UTC:
INITIAL 24    36    48    60    72    84    96    TYPE      SOF
48W     51W   55W   59W   64W   67W   70W   73W    TW       22N
64W     68W   72W   76W   80W   84W   88W   92W    EW       18N
74W     78W   82W   85W   88W   91W   94W   98W    EW       22N
80W     83W   86W   89W   92W   95W   98W  101W    TW       14N

A TROPICAL WAVE EXTENDS ALONG 48W AND SOUTH OF 18N. THIS REACHES
THE ISLAND CHAIN EARLY ON THURSDAY MORNING. AS IT ENTERS THE
EASTERN CARIBBEAN THE WAVE IS EXPECTED TO INTERACT WITH
AFOREMENTIONED TUTT/TUTT LOW OVER THE NORTHEAST CARIBBEAN. THIS
WILL FAVOR THE NORTHWARD MODULATION OF THE ITCZ ACROSS THE
WINDWARD TO THE SOUTHERN FRENCH ISLES LATER IN THE WEEK...TO
SUSTAIN A SURGE IN CONVECTION. THIS WILL SUSTAIN 05-10MM/DAY AND
MAXIMA OF 15-20 IN THE NORTHEASTERN ANTILLES...AND MAXIMA OF
15-25MM IN PUERTO RICO AND HISPANIOLA.

AN EASTERLY WAVE ALONG 64W WILL STREAM ACROSS VENEZUELA ON TUESDAY
TO ENHANCE CONVECTION IN NORTHWEST VENEZUELA/NORTHERN
COLOMBIA...WHERE IT WILL LEAD TO 15-20MM/DAY AND MAXIMA OF
30-60MM/DAY THROUGH EARLY WEDNESDAY. THE WAVE WILL ENHANCE
ACTIVITY IN PANAMA/WESTERN COLOMBIA ON WEDNESDAY-EARLY THURSDAY
WHERE IT WILL SUSTAIN MAXIMA NEAR/UNDER 15-20MM/DAY...AND
NICARAGUA/HONDURAS ON THURSDAY-FRIDAY WHERE IT WILL SUSTAIN
15-20MM/DAY AND MAXIMA OF 30-60MM. THIS WILL ALSO STIMULATE
CONVECTION IN SOUTHERN HONDURAS/EL SALVADOR IN THE EVENING TO
SUSTAIN 15-20MM/DAY AND MAXIMA OF 25-50MM.

AN EASTERLY WAVE ALONG 74W...SOUTH OF 22N...AND NORTH OF 17N IS
RAPIDLY PROPAGATING ACROSS THE GREATER ANTILLES. IT WILL STIMULATE
CONVECTION IN SOUTHEASTERN CUBA ON WEDNESDAY TO SUSTAIN MAXIMA OF
15-20MM...AND ON WEDNESDAY IT WILL FAVOR MAXIMA OF 20-35MM/DAY IN
WESTERN AND CENTRAL CUBA.

AN ILL-DEFINED TROPICAL WAVE ALONG 80W WILL CONTINUE INTERACTING
WITH THE ITCZ ACROSS PANAMA AND COSTA RICA EARLY IN THE CYCLE TO
SUSTAIN MAXIMA OF 20-40MM IN WESTERN PANAMA AND COSTA RICA ON
TUESDAY. BY WEDNESDAY-THURSDAY ENHANCEMENT WILL CLUSTER IN EL
SALVADOR AND SOUTHERN GUATEMALA WHERE EXPECTING 10-15MM/DAY AND
MAXIMA OF 20-30MM. BY THURSDAY-FRIDAY ENHANCEMENT WILL CLUSTER IN
SOUTHERN MEXICO WHERE EXPECTING MAXIMA OF 20-35MM.

WARD-FORBES...BDM (THE BAHAMAS)
HERNANDEZ...IMTA (MEXICO)
TEJADA...AAC (PANAMA)
GALVEZ...WPC (USA)