894
FXCA20 KWBC 201813
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
212 PM EDT THU JUL 20 2023
FORECAST BULLETIN FROM 20 JUL 2023 AT 1815 UTC: ACCELERATED TRADES
CONTINUE ACROSS THE CARIBBEAN...IN ASSOCIATION WITH THE MID-SUMMER
DROUGHT AND A LARGE SCALE UPPER CONVERGENT PATTERN OVER THE
AMERICAS. ALTHOUGH AVAILABLE MOISTURE CONTINUES LIMITED ACROSS
MOST OF THE CARIBBEAN INTO THE GULF OF MEXICO AND EXTENSIVE AREAS
OF CENTRAL AND NORTHERN MEXICO...THE ENHANCED LOW-LEVEL MOISTURE
CONVERGENCE IN THE EXIT REGION OF THE CARIBBEAN LOW-LEVEL JETS IS
EXPECTED TO AID WITH A GRADUAL INCREASE IN PRECIPITABLE WATER.
THIS WILL FAVOR AN INCREASE IN THE COVERAGE OF PRECIPITATION IN
MEXICO THROUGH THE FORECAST CYCLE. IN THE UPPER LEVELS...THE
SUBTROPICAL RIDGE IS FORECAST TO REMAIN OVER THE SOUTHWEST USA
WHILE A TUTT LOW RETROGRADES FROM THE YUCATAN PENINSULA INTO
CENTRAL MEXICO THROUGH THE CYCLE...PROVIDINT LOCAL ENHANCEMENT.
THIS...IN COMBINATION WITH TROPICAL WAVE ACTIVITY WILL FAVOR
AFTERNOON CONVECTION IN AREAS SOUTH OF 21N ON A DAILY BASIS. ON
THURSDAY...THE HEAVIEST PRECIPITATION IS EXPECTED IN SOUTHEAST
MEXICO WHERE 20-40MM IS FORECAST FOR MAXIMA. ON FRIDAY...EXPECT
MAXIMA OF 25-50MM IN OAXACA/GUERRERO AND MAXIMA OF 20-35MM
ELSEWHERE FROM SOUTHEAST MEXICO INTO JALISCO/COLIMA. ON SATURDAY
EXPECT MAXIMA OF 20-40MM IN CHIAPAS/TABASCO NAD MAXIMA OF 20-35MM
IN AREAS WEST. PRECIPITATION ALONG THE SIERRA MADRE OCCIDENTAL
WILL...HOWEVER...CONTINUE TO OCCUR IN AN ISOLATED MANNER.
TO THE EAST...A PROMINENT SAHARAN AIR LAYER CONTINUES PROPAGATING
WESTWARD ACROSS THE LESSER ANTILLES AND NORTHERN
CARIBBEAN/BAHAMAS...AND IS FORECAST TO REACH THE YUCATAN PENINSULA
AND SOUTHEAST GULF OF MEXICO BY SATURDAY MORNING. THIS WILL
CONTINUE TO REINFORCE THE CURRENT DRY WEATHER PATTERN ACROSS THE
REGION...FAVORING VERY LITTLE PRECIPITATION. THE LARGEST AMOUNTS
ARE EXPECTED ON FRIDAY...WHERE A TROUGH ASSOCIATED WITH THE
WEAKENED LEADING EDGE OF THE SAL...WILL FAVOR MAXIMA OF 15-25MM IN
CUBA AND THE CAYMAN ISLANDS. NOTE THAT THE SAL IS FORECAST TO
REACH NORTHERN CENTRAL AMERICA AS WELL...REACHING THE CONTINENTAL
DIVIDE LATE ON SUNDAY.
DRY CONDITIONS CONTINUE IN CENTRAL AND SOUTHERN PORTIONS OF
CENTRAL AMERICA DUE TO ACCELERATED TRADES...LARGE SCALE UPPER
CONVERGENCE AND THE EFFECTS OF EL NINO ON THE ACCELERATION OF THE
GAP FLOWS. THE DRY CONDITIONS ARE FORECAST TO GRADUALLY CHANGE
INTO A MORE SEASONAL WEATHER PATTERN...AS A TROPICAL WAVE ENTERS
PANAMA ON FRIDAY AND CROSSES COSTA RICA ON SUNDAY. EXPECT VERY
ISOLATED CONVECTION ON THURSDAY...PRIMARILY IN THE CARIBBEAN BASIN
OF COSTA RICA AND NICARAGUA...WHERE EXPECT VERY ISOLATED MAXIMA OF
15-25MM. ON FRIDAY EXPECT MAXIMA OF 15-30MM IN PANAMA AND COSTA
RICA...WHILE TRADE WIND CONVERGENCE FAVORS MAXIMA OF 20-35MM IN
EASTERN NICARAGUA/HONDURAS. ON SATURDAY EXPECT MAXIMA OF 20-35MM
IN PANAMA/SOUTHERN COSTA RICA...AND MAXIMA OF 20-45MM IN EASTERN
HONDURAS/EASTERN NICARAGUA WITH THE TROPICAL WAVE. IN EL
SALVADOR/GUATEMALA/BELIZE...EXPECT ALSO MAXIMA OF 20-45MM DUE TO
AN INCREASE IN PRECIPITABLE WATER AND AN INCREASE IN VENTILATION
BETWEEN A TUTT LOW IN THE PACIFIC AND AN UPPER RIDGE LOCATED EAST
OF BELIZE.
IN NORTHERN SOUTH AMERICA...THE WETTEST CONDITIONS ARE EXPECTED
WITH A TROPICAL WAVE THAT IS PROPAGATING ACROSS WESTERN
VENEZUELA/EASTERN COLOMBIA ON THURSDAY. INITIALLY...ENHANCEMENT
WILL MOSTLY PEAK EAST OF THE ANDES...GIVEN THE INFLUENCE OF STRONG
EAST-SOUTHEASTERLY WINDS IN THE MID TROPOSPHERE. THESE WILL
CONTINUE TO ENHANCE WIND SHEAR AND ADIABATIV WARMING AND DRYING IN
MOST OF CENTRAL AND NORTHWEST COLOMBIA ON THURSDAY. YET...A
WEAKENING OF THE WINDS AND INTERACTION BETWEEN THE TROPICAL WAVE
AND A TUTT IN THE SOUTHERN CARIBBEAN WILL FAVOR MAXIMA OF 30-60MM
IN MOST OF NORTHERN COLOMBIA AND NORTHWEST VENEZUELA ON FRIDAY.
THIS DECREASES THEREAFTER.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 21/00 21/12 22/00 22/12 23/00 23/12 24/00 24/12
TW 13N 69W 73W 76W 79W 81W 84W 86W 89W 92W
TW 25N 89W 92W 94W 97W 100W 102W 105W 107W 109W
TW 23N 105W 109W 112W 116W EXITS
A TROPICAL WAVE IS INITIALIZED AT 69W AND SOUTH OF 13N. ON
THURSDAY IT WILL FAVOR MAXIMA OF 20-40MM IN THE WESTERN VENEZUELAN
ORINOQUIA. ON FRIDAY...IT WILL FAVOR MAXIMA OF 30-60MM IN NORTHERN
COLOMBIA AND THE DARIEN AND MAXIMA OF 15-30MM IN PANAMA. ON
SATURDAY...IT WILL FAVOR MAXIMA OF 20-45MM IN EASTERN NICARAGUA
AND HONDURAS...AND GENERALIZED MAXIMA OF 15-35MM IN CENTRAL
PORTIONS OF HONDURAS...NICARAGUA..AND COSTA RICA.
A TROPICAL WAVE IS INITIALIZED AT 89W AND SOUTH OF 25N. ON
THURSDAY EXPECT MAXIMA OF 20-40MM FROM WESTERN
HONDURAS/GUATEMALA/BELIZE INTO SOUTHERN VERACRUZ AND NORTH INTO
THE WESTERN YUCATAN PENINSULA. ON FRIDAY...THE WAVE WILL FAVOR
MAXIMA OF 25-50MM IN GUERRERO AND WEST OAXACA. ON SATURDAY...THE
WAVE WILL FAVOR MAXIMA OF 20-35MM IN PORTIONS OF SOUTHWEST MEXICO.
A TROPICAL WAVE IS INITIALIZED AT 105W AND SOUTH OF 23N. THIS WAVE
IS PROPAGATING VERY RAPIDLY...LIMITING ITS EFFECTS ON CONVECTION.
IT WILL HAVE LIMITED EFFECTS TO THE CONTINENT AND EXITS THE
FORECAST AREA BY FRIDAY.
GALVEZ/ACOSTA...WPC (USA)
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