Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3
000
FXCA20 KWBC 201758
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 PM EDT THU JUL 20 2017

TROPICAL DISCUSSION FROM JUL 20/12 UTC: UNDER INFLUENCE OF BROAD
MID/UPPER LEVEL RIDGE OVER THE CENTRAL USA...AN UPPER LEVEL LOW IS
TO RETROGRESS ACROSS GEORGIA/FLORIDA TO THE NORTHERN GULF OF
MEXICO LATER ON FRIDAY. MEANWHILE...AS IT MEANDERS ACROSS THE
FLORIDA PENINSULA THIS IS TO ENHANCE CONVECTIVE DEVELOPMENT ACROSS
THE NORTHWEST BAHAMAS...WHERE WE EXPECT RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-30MM. ON FRIDAY THIS DECREASES TO
05-10MM/DAY AND MAXIMA OF 15-25MM...WITH LESSER AMOUNTS ON
SATURDAY AS A DRYER AIR MASS ADVECTS ACROSS THE BAHAMAS.

SOUTH OF THE MID/UPPER LEVEL RIDGE...TUTT/TUTT LOWS POPULATE THE
GULF-NORTHERN STATES OF MEXICO. ONE OVER NORTHERN MEXICO IS TO
MEANDER BETWEEN COAHUILA/ TAMAULIPAS-NUEVO LEON WHILE GRADUALLY
WEAKENING ON SATURDAY. ANOTHER OVER THE GULF...MEANWHILE...IS TO
INITIALLY EXTEND ACROSS THE YUCATAN/SOUTHERN STATES OF MEXICO. ON
FRIDAY THIS IS TO MEANDER WEST INTO THE CAMPECHE SOUND...WHERE IT
IS TO THEN MEANDER THROUGH SATURDAY EVENING. THIS IS TO THEN MERGE
WITH AFOREMENTIONED MID/UPPER LEVEL LOW/TROUGH RETROGRESSING
ACROSS THE NORTHERN GULF...TO EVOLVE INTO A BROAD TROUGH DURING
THE WEEKEND. ACROSS SONORA-WESTERN CHIHUAHUA IN WESTERN MEXICO
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM
DURING THE NEXT FEW DAYS. OVER SINALOA INITIALLY EXPECTING
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. THROUGH
SATURDAY THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-25MM. OVER
NORTHEAST MEXICO THE WANING UPPER LEVEL TROUGH IS TO FAVOR
ISOLATED CONVECTION ACROSS COAHUILA-TAMAULIPAS...WITH ACCUMULATION
OF 00-05MM/DAY AND MAXIMA OF 10MM OVER THE NEXT COUPLE OF DAYS. ON
SATURDAY...AS A DEEPER TROUGH MEANDERS INTO THE NORTHWEST
GULF...THIS INCREASES TO 05-10MM/DAY AND MAXIMA OF 15MM.. HIGHER
AMOUNTS ARE EXPECTED TO THE SOUTH...ACROSS COLIMA-NAYARIT-GUERRERO
AND CENTRAL MEXICO...WITH ACCUMULATION OF 05-10MM/DAY AND MAXIMA
OF 15-25MM THROUGHOUT THE CYCLE. ON THE SOUTHERN STATES OF MEXICO
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. BUT
AS THE UPPER LEVEL TROUGH MEANDERS TO THE CAMPECHE SOUTH ON FRIDAY
IT IS TO THEN PHASE WITH TRADE WIND SURGE TO SUSTAIN SCATTERED
CONVECTION...TO TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA
OF 20-30MM.

A BROAD CELL OF THE SUBTROPICAL RIDGE DOMINATES THE MID LEVELS
OVER THE WESTERN ATLANTIC/NORTHERN CARIBBEAN ISLES...WHILE
CENTERING ON A CLOSED HIGH THAT IS TO MEANDER JUST SOUTH OF
BERMUDA. BROAD MID LEVEL RIDGE PATTERN IS FORECAST TO HOLD DURING
THE NEXT FEW DAYS. AS IT MEANDERS OVER THE NORTHERN CARIBBEAN
ISLES THIS IS TO SUSTAIN A FAIRLY STRONG TRADE WINDS CAP DURING
THE NEXT COUPLE OF DAYS THAT IS TO WEAKEN LATER DURING THE
WEEKEND. MEANWHILE...THIS WILL COMBINE WITH A DRY SAHARAN AIR
LAYER ENTRAINING ACROSS THE NORTHERN CARIBBEAN TO GENERALLY FAVOR
FAIR WEATHER CONDITIONS. LIGHT CONVECTION OVER THE LARGER ISLANDS
IS TO ONLY TRIGGER RAINFALL AMOUNTS OF 00-05MM/DAY AND WIDELY
ISOLATED MAXIMA OF 10MM.

AT UPPER LEVELS THE SUBEQUATORIAL RIDGE LIES FARTHER SOUTH ACROSS
THE BASIN...WITH AXIS WEST ACROSS THE TROPICAL ATLANTIC-ISLAND
CHAIN TO THE CARIBBEAN/CENTRAL AMERICA. THIS IS VENTING CONVECTION
ALONG THE ITCZ-NEAR EQUATORIAL TROUGH OVER SOUTHERN CENTRAL
AMERICA-NORTHERN SOUTH AMERICA. OVER HONDURAS-NICARAGUA INITIALLY
EXPECTING RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM.
THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15MM ON
FRIDAY-SATURDAY. ACROSS PANAMA-COSTA RICA INITIALLY EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. THROUGH
FRIDAY THIS INCREASES TO 15-20MM/DAY AND MAXIMA OF 25-50MM AS THE
ITCZ MEANDERS OVER THE ISTHMUS...WHILE ON SATURDAY THE MAXIMA IS
TO PEAK AT 20-40MM. ON THE WESTERN PLAINS OF COLOMBIA/ANDEAN
REGION ONLY EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA
OF 15-25MM. OVER NORTHERN COLOMBIA-EASTERN PLAINS AND VENEZUELA
INITIALLY EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-45MM/DAY. ON FRIDAY-SATURDAY THE RAINFALL AMOUNTS OVER WESTERN
VENEZUELA-EASTERN COLOMBIA DECREASE TO 05-10MM/DAY AND MAXIMA OF
15-25MM...WHILE TO THE EAST MAXIMA IS TO PEAK AT 20-40MM IN
SCATTERED CONVECTION. OVER THE GUIANAS SEA BREEZE/DIURNAL
CONVECTION IS TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA
OF 15-20MM...WITH MOST ACTIVE ALONG THE COAST.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24     36     48     60     72     84     96     TYPE
51W      53W    56W    59W    61W    63W    66W    69W     TW
59W      62W    66W    70W    73W    77W    81W    85W     EW
77W      80W    83W    87W    90W    94W    97W   100W     TW
84W      88W    91W    94W    97W    99W   100W   102W    TWS
101W    104W   107W   111W   113W   114W   115W   117W     TW

A TROPICAL WAVE ALONG 51W AND SOUTH OF 25N IS TO TRIGGER SCATTERED
CONVECTION ACROSS NORTHERN FRENCH GUIANA-SURINAME...WITH RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. SIMILAR AMOUNTS ARE
EXPECTED OVER GUYANA ON FRIDAY...WHILE OVER EASTERN VENEZUELA IT
IS TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-40MM. OVER THE LESSER ANTILLES THIS IS TO INITIALLY FAVOR
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. ON
SATURDAY-SUNDAY THIS INCREASES TO 05-10MM/DAY AND MAXIMA OF 15MM.
OVER THE NORTHERN LEEWARD-VIRGIN ISLES TO PUERTO RICO THIS THEN
INCREASES TO 05-10MM/DAY AND MAXIMA OF 15-30MM.

AN EASTERLY WAVE ALONG 59W AND SOUTH OF 20N IS TO SUSTAIN ISOLATED
CONVECTION ACROSS THE LESSER ANTILLES TO EASTERN PUERTO
RICO...WITH ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF 10MM. OVER
VENEZUELA IN INTERACTION WITH THE NET IT IS TO SUSTAIN RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-45MM.  AS IT MOVES ACROSS
HISPANIOLA ON FRIDAY THIS IS TO ALSO TRIGGER RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM...WHILE OVER NORTHWEST
VENEZUELA-NORTHERN COLOMBIA EXPECTING RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-25MM. ON SATURDAY THIS IS TO THEN
TRIGGER ISOLATED TO SCATTERED CONVECTION ACROSS JAMAICA-EASTERN
CUBA WITH RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM.
ACROSS COLOMBIA TO THE DARIEN IN EASTERN PANAMA EXPECTING RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.

A TROPICAL WAVE ALONG 77W AND SOUTH OF 16N IS TO SUSTAIN SCATTERED
CONVECTION ACROSS PANAMA-COSTA RICA WITH RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM. HIGHER AMOUNTS ARE EXPECTED
OVER NICARAGUA TO EASTERN HONDURAS...WHERE THIS IS TO SUSTAIN
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. ON FRIDAY
THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15MM AS IT SPREADS
WEST ACROSS HONDURAS... WHILE OVER EL SALVADOR-GUATEMALA EXPECTING
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. ON
SATURDAY...OVER SOUTHERN-CENTRAL MEXICO THIS WILL SUSTAIN RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.

THE LEADING EDGE OF A TRADE WINDS SURGE IS INITIALIZED ALONG 84W.
AS IT MOVES ACROSS BELIZE-GUATEMALA TO SOUTHERN MEXICO THIS IS TO
INITIALLY TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15MM. ON FRIDAY THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF
20-30MM. ON SATURDAY FOCUS OF THE CONVECTION SHIFTS TO CENTRAL
MEXICO WHERE IT IS TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-25MM.

A TROPICAL WAVE ALONG 101W AND SOUTH OF 21N WILL SUSTAIN SCATTERED
CONVECTION ACROSS SOUTHWEST MEXICO WITH ACCUMULATION OF
05-10MM/DAY AND MAXIMA OF 15-25MM THROUGH FRIDAY MORNING.

GAJADHAR...SLMS (SAINT LUCIA)
DAVISON...WPC (USA)
$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.