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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1828Z Jul 17, 2018)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
228 PM EDT TUE JUL 17 2018

TROPICAL DISCUSSION FROM JUL 17/12 UTC: CONSISTENT WITH PREVIOUS
FORECAST...AT 250 HPA...BROAD RIDGE EXTENDS FROM THE SOUTHWEST
USA/NORTHERN MEXICO TO THE NORTHERN GULF/SOUTHERN USA. THE RIDGE
IS TO HOLD NEARLY UNCHANGED DURING THE NEXT TWO DAYS...THEN START
TO WEAKEN FROM THE EAST AS A TROUGH DEEPENS ACROSS THE EASTERN
USA/WESTERN ATLANTIC. MEANWHILE...THE RIDGE IS STEERING A
TUTT/TUTT LOW ACROSS THE CENTRAL-NORTHWEST STATES OF MEXICO...WITH
AXIS TO RELOCATE TO THE GULF OF CORTEZ/BAJA PENINSULA LATER ON
WEDNESDAY. ON THURSDAY IT IS TO THEN MOVE FARTHER TO THE WEST INTO
THE EASTERN PACIFIC. AS IT MEANDERS WEST...THE TROUGH IS TO
ENHANCE DIURNAL CONVECTION ACROSS SONORA/NORTHERN SINALOA AND THE
BAJA PENINSULA...TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-45MM. ON WEDNESDAY-THURSDAY...AS THE TROUGH MOVES
WEST...DIURNAL ACTIVITY ALONG THE SIERRA MADRE WILL DECREASE TO
05-10MM/DAY AND MAXIMA OF 15-20MM/DAY.

ANOTHER TUTT TO THE SOUTH OF THE SUBTROPICAL RIDGE EXTENDS WEST
FROM CUBA INTO THE YUCATAN/SOUTHERN STATES OF MEXICO. AS THE
SUBTROPICAL RIDGE STRENGTHENS TO THE NORTH THIS WILL DRIVE THE
TUTT SOUTH INTO THE NORTHWEST CARIBBEAN...WITH AXIS TO BECOME
BETTER ORGANIZED ON WEDNESDAY-THURSDAY...WHEN IT WILL CENTER ON A
CLOSED LOW SOUTH-SOUTHWEST OF JAMAICA-CAYMAN BRAC. A SECONDARY LOW
ALSO FORMS TO THE WEST ALONG THE SOUTH COAST OF MEXICO. THIS IS TO
MEANDER TO THE WEST-SOUTHWEST LATER IN THE WEEK. OVER CUBA THE
TROUGH ALOFT IS TO ENHANCE DIURNAL CONVECTION TO FAVOR RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM THROUGH ??. AS THE
TROUGH BECOMES BETTER ORGANIZED ON THURSDAY...THIS WILL ENHANCE
CONVECTION ACROSS JAMAICA TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 15MM. ON FRIDAY THIS INCREASES TO MAXIMA OF 15-20MM.
OVER GUATEMALA-SOUTHERN MEXICO EXPECTING RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-25MM THROUGH WEDNESDAY MORNING.
HIGHER AMOUNTS ARE EXPECTED LATER IN THE DAY AS A TROPICAL WAVE
STREAMS ACROSS CENTRAL AMERICA-SOUTHERN MEXICO.

ALSO AT 250 HPA...BROAD CELL OF THE SUBEQUATORIAL RIDGE EXTENDS
FROM CENTRAL AMERICA TO THE EASTERN CARIBBEAN/NORTHERN SOUTH
AMERICA. THROUGH WEDNESDAY MORNING...A DEEPENING TROUGH OVER THE
CENTRAL ATLANTIC IS TO AMPLIFY INTO THE NORTHEAST CARIBBEAN. THIS
IS TO REACH MAXIMUM AMPLITUDE ON THURSDAY-FRIDAY...WITH AXIS TO
THEN CENTER ON A CLOSED LOW TO THE NORTHEAST OF THE LEEWARD
ISLANDS. AS THE TROUGH DEEPENS AND PRESSES AGAINST THE
SUBEQUATORIAL RIDGE TO THE SOUTH...THE RIDGE IS EXPECTED TO
RAPIDLY COLLAPSE LATER TODAY. ALTHOUGH THIS PORTIONS COLLAPSES THE
SEGMENT OVER THE SOUTHERN/WESTERN CARIBBEAN IS TO HOLD DURING THE
NEXT COUPLE OF DAYS. AS THE TROUGH DEEPENS ACROSS THE NORTHEAST
CARIBBEAN...EXPECTING THE SLOW AND GRADUAL EROSION OF THE TRADE
WINDS CAP LATER ON WEDNESDAY/EARLY ON THURSDAY MORNING. ON
THURSDAY THE CAP RELAXES ITS FOOTHOLD AND THE ENVIRONMENTAL
CONDITIONS WILL BECOME MORE FAVORABLE AND CONDUCIVE FOR DEEPER
CONVECTION TO DEVELOP. THE SUBEQUATORIAL RIDGE...AS IT HOLDS TO
THE WEST...WILL VENT DEEP CONVECTION ACROSS CENTRAL AMERICA...WITH
ACTIVITY ACROSS HONDURAS-NORTHERN NICARAGUA TO SUSTAIN RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. HIGHER AMOUNTS ARE
EXPECTED OVER SOUTHERN CENTRAL AMERICA. OVER COSTA RICA/SOUTHERN
NICARAGUA EXPECTING ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF
20-45MM/DAY. THROUGH THURSDAY THIS WILL INCREASE AS ENHANCED BY A
TROPICAL WAVE (SEE BELOW FOR DETAILS). OVER
PANAMA-NORTHERN/WESTERN COLOMBIA EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-30MM...WITH HIGHER AMOUNTS IN
ASSOCIATION WITH A TROPICAL WAVE ON THURSDAY. OVER EASTERN
COLOMBIA-SOUTHERN VENEZUELA...EXPECTING RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 30-60MM. THROUGH THURSDAY THIS DECREASES
TO 10-15MM/DAY AND MAXIMA OF 20-45MM...SURGING AGAIN ON FRIDAY TO
MAXIMA OF 30-60MM. OVER THE GUIANAS EXPECTING RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM.

TROPICAL/EASTERLY WAVES/TRADE WIND SURGES FROM 00 UTC:
INITIAL 24    36    48    60    72    84    96    TYPE      SOF
49W     54W   59W   64W   69W   74W   79W   84W    TW       24N
78W     83W   87W   91W   94W   97W  100W  103W    TW       20N
101W   104W  108W  112W   DISSIPATES               EW       20N

A PROGRESSIVE TROPICAL WAVE IS INITIALIZED ALONG 49W AND SOUTH OF
24N. THE WAVE REACHES FRENCH GUIANA EARLY IN THE CYCLE...TO
SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM.
THIS SPREADS ACROSS SURINAME TO GUYANA ON WEDNESDAY. ACROSS
EASTERN VENEZUELA THIS WILL SUSTAIN RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM...WHILE OVER WESTERN
VENEZUELA-EASTERN/NORTHERN COLOMBIA THIS WILL RESULT IN RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-45MM. ON FRIDAY THE MAXIMA
IN THIS AREA INCREASES TO 30-60MM. ACROSS THE ISLAND CHAIN THIS
WILL TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM
ON WEDNESDAY...WITH CONVECTION TO AFFECT THE VIRGIN ISLES EARLY ON
THURSDAY MORNING. ACROSS PUERTO RICO AND HISPANIOLA THIS WILL THEN
INCREASE TO 10-15MM/DAY AND MAXIMA OF 20-45MM ON THURSDAY
AFTERNOON. AS IT ENTERS JAMAICA THE WAVE WILL PHASE WITH THE TUTT
ALOFT TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-25MM. ON FRIDAY THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF
20-35MM. ACROSS COSTA RICA EXPECTING ACCUMULATION OF 15-20MM/DAY
AND MAXIMA OF 25-50MM...WHILE OVER NORTHEAST NICARAGUA/NORTHEAST
HONDURAS EXPECT ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-20MM.

A TROPICAL WAVE ALONG 78W AND SOUTH OF 20N IS TO TRIGGER SCATTERED
CONVECTION ACROSS NORTHERN COLOMBIA/NORTHWEST VENEZUELA EARLY IN
THE CYCLE...WITH ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF
30-60MM. OVER WESTERN COLOMBIA...IN INTERACTION WITH THE
PANAMANIAN LOW...THIS WILL THEN SUSTAIN RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-45MM. OVER JAMAICA-EASTERN CUBA
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM ON
TUESDAY-WEDNESDAY. OVER COSTA RICA-SOUTHERN NICARAGUA THIS IS TO
INTERACT WITH THE ITCZ IN SUPPORT OF RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-45MM. ACROSS
HONDURAS-BELIZE-GUATEMALA THIS IS TO THEN SUSTAIN RAINFALL AMOUNTS
OF 10-15MM/DAY AND MAXIMA OF 20-35MM. ON THE SOUTHERN AND CENTRAL
STATES OF MEXICO EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM ON THURSDAY...WITH SIMILAR AMOUNTS OVER CENTRAL
MEXICO ON FRIDAY.

AN EASTERLY WAVE ALONG 101W AND SOUTH OF 20N IS TO ENHANCE
CONVECTION ACROSS THE SOUTHWEST STATES OF MEXICO...TO FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.

HUDSON...MS (JAMAICA)
HERNANDEZ...IMTA (MEXICO)
WARD-FORBES...BDM (THE BAHAMAS)
DAVISON...WPC (USA)