907
FXCA20 KWBC 171839
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
239 PM EDT MON JUL 17 2023
FORECAST BULLETIN FROM 17 JUL 2023 AT 1840 UTC: NORTHWEST IN THE
DOMAIN...DRIER CONDITIONS ARE DEVELOPING OVER MEXICO AS A DRY AIR
MASS IS ADVECTED FROM THE EAST. THIS WILL LIMIT PRECIPITATION
PRIMARILY TO AREAS TO THE SOUTH OF 21N. THE SIERRA MADRE
OCCIDENTAL WILL SEE AFTERNOON CONVECTION ON A DAILY BASIS...BUT
THE LIMITED AMOUNTS OF AVAILABLE MOISTURE WILL YIELD TO VERY LIGHT
AND ISOLATED DIURNAL ACCUMULATIONS.
TO THE EAST...UNDER THE INFLUENCE OF A ROBUST HIGH OVER THE NORTH
ATLANTIC NEAR 33N 53W...EXPECT ACCELERATED TRADES TO CONTINUE
ACROSS THE TROPICAL NORTH ATLANTIC AND INTO THE CARIBBEAN. THESE
ARE ACCOMPANIED BY A SAHARAN AIR LAYER (SAL). THIS WILL FAVOR
WINDY AND DUSTY CONDITIONS ESPECIALLY ALONG THE NORTHERN
CARIBBEAN. THE SAL IS FORECAST TO ENTER THE NORTHEAST CARIBBEAN
LATE ON MONDAY...REACHING THE GULF OF HONDURAS REGION BY
THURSDAY...EXERTING ITS STRONGEST IMPACTS IN THE GREATER ANTILLES.
NOTE THAT A TROPICAL WAVE IS PROPAGATING AHEAD OF THE SAL (SEE
BELOW FOR POSITIONS AND RAINFALL AMOUNTS).
WETTER CONDITIONS ARE EXPECTED FOR PORTIONS OF CENTRAL AMERICA.
YET...AS THE MID-SUMMER DROUGHT/CANICULA AND ASSOCIATED
ACCELERATED TRADES CONTINUE...EXPECT THE DRYING TREND IN THE
PACIFIC BASINS OF NORTHERN CENTRAL AMERICA TO CONTINUE INCREASING
IN STRENGTH. THIS WILL LIMIT THE HEAVIEST PRECIPITATION TO THE
CARIBBEAN BASIN...PARTICULARLY IN AREAS SOUTH OF 15N...WHERE
DEEP-LAYER MOISTURE REMAINS IN PLACE. TROPICAL WAVES WILL PLAY A
ROLE IN THE VARIABILITY OF PRECIPITATION...ESPECIALLLY IN
NICARAGUA AND EASTERN HONDURAS (SEE BELOW). YET IN COSTA RICA AND
PANAMA...EXPECT A DRYING TREND IN ASSOCIATION WITH THE
ACCELERATION OF THE LOW-LEVEL WINDS. THIS INCLUDES THE DEVELOPMENT
OF NORTHERLY TRADES ACROSS PANAMA ON TUESDAY AND
WEDNESDAY...UNUSUAL FOR THE TIME OF THE YEAR. THESE NORTHERLY
TRADES AND DRY AIR ADVECTION INTO THE REGION WILL NOT ONLY FAVOR A
DECREASE IN PANAMA AND COSTA RICA...BUT ALSO IN NORTHWEST
COLOMBIA...WHERE EXPECT A NOTICEABLE DECREASE IN THE COVERAGE OF
CONVECTION ON TUESDAY AND WEDNESDAY.
LASTLY...A WEAK TROPOSPHERIC KELVIN WAVE IS PROPAGATING WESTWARD
ON MONDAY...INTERACTING WITH THE NET AND A TROPICAL WAVE IN
NORTHWEST SOUTH AMERICA. THIS WILL FAVOR MAXIMA OF 25-50MM IN THE
WESTERN ORINOQUIA OF VENEZUELA...AND IN INTERIOR PORTIONS OF
NORTHERN COLOMBIA/ANTIOQUIA ON MONDAY. ON TUESDAY...THE KELVIN
WILL INTERACT WITH A TROPICAL WAVE ENTERING GUYANA...TO FAVOR
MAXIMA OF 20-40MM IN GUYANA AND MOST OF CENTRAL AND SOUTHERN
VENEZUELA. THE KELVIN IS THEN FOREACST TO ENTER THE TROPICAL
ATLANTIC.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 18/00 18/12 19/00 19/12 20/00 20/12 21/00 21/12
TW 13N 51W 54W 57W 59W 62W 65W 67W 70W 73W
TW 22N 67W 70W 74W 78W 81W 83W 85W 88W 91W
TW 16N 81W 84W 88W 93W 98W 103W 107W 111W 115W
TW 21N 100W 103W 106W 109W 112W 115W EXITS
A TROPICAL WAVE IS INITIALIZED AT 51W AND SOUTH OF 13N. IT WILL
FAVOR MAXIMA OF 15-20MM IN FRENCH GUIANA AND SURINAME ON MONDAY.
ON TUESDAY IT WILL FAVOR MAXIMA OF 20-35MM IN THE WINDWARD ISLANDS
AND MAXIMA OF 20-45MM IN GUYANA AND EASTERN VENEZUELA. ON
WEDNESDAY IT WILL FAVOR MAXIMA OF 30-60MM IN NORTH-CENTRAL
VENEZUELA AND MAXIMA OF 20-45MM IN SOUTH-CENTRAL VENEZUELA.
A LARGE TROPICAL WAVE IS INITIALIZED AT 67W AND SOUTH OF 22N. IT
WILL PROPAGATE RAPIDLY ACROSS THE CARIBBEAN IN ASSOCIATION WITH
THE ACCELERATED TRADES...AND IS BEING TRAILED BY A STRONG SAHARAN
AIR LAYER...FORECAST TO BE THE MOST DENSE ACROSS THE GREATER
ANTILLES. ON MONDAY...THE WAVE WILL FAVOR MAXIMA OF 20-45MM IN
EASTERN PUERTO RICO AND IN HISPANIOLA. IN THE WESTERN ORINOQUIA IT
WILL FAOVR MAXIMA OF 25-50MM. ON TUESDAY IT WILL FAVOR MAXIMA OF
20-35MM IN CENTRAL AND EASTERN CUBA...AND MAXIMA OF 15-20MM IN
JAMAICA...CAYMAN ISLANDS AND IN THE NORTHWEST BAHAMAS. ON
WEDNESDAY...IT WILL FAVOR MAXIMA OF 20-40MM IN EASTERN
HONDURAS/EAST NICARAGUA AND CARIBBEAN ISLANDS...WHILE IN WESTERN
CUBA IT FAVORS MAXIMA OF 20-35MM. IN THE CAYMAN ISLANDS EXPECT
MAXIMA OF 15-20MM.
A TROPICAL WAVE IS INITIALIZED NEAT 81W AND SOUTH OF 16N. THIS
WAVE WILL CROSS CENTRAL AMERICA ON MONDAY...TO PROPAGATE WESTWARD
VERY RAPIDLY BECOMING ILL-DEFINED ACROSS THE TROPICAL PACIFIC. ON
MONDAY...EXPECT THE HEAVIEST PRECIPITATION IN NICARAGUA/CARIBBEAN
ISLANDS...WHERE ENHAN CED TRADE WIND CONVERGENCE WILL ADD TO THE
EFFECTS OF THE WAVE TO FAVOR 15-20MM/DAY AND MAXIMA OF 35-70MM. IN
SOUTH COSTA RICA EXPECT MAXIMA OF 25-50MM. ON TUESDAY IT WILL
FAVOR MAXIMA OF 15-20MM IN SOUTHERN GUATEMALA/CHIAPAS AND
CAMPECHE...WHILE ON WEDNESDAY IT FAVORS MAXIMA OF 15-25MM IN
SOUTHWEST MEXICO.
A TROPICAL WAVE INITIALIZED NEAR 100W ON MONDAY WILL FAVOR MAXIMA
OF 20-35MM IN SOUTHWEST MEXICO THROUGH EARLY TUESDAY...TO THEN
RAPIDLY LIMITS ITS IMPACTS IN CONTINENTAL REGIONS.
GALVEZ/ACOSTA/ALAMO...WPC (USA)
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