877
FXCA20 KWBC 191751
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 PM EDT WED JUL 19 2023
FORECAST BULLETIN FROM 19 JUL 2023 AT 1800 UTC: THE INFLUENCE OF
THE MID-SUMMER DROUGHT/CANICULA AND LARGE SCALE UPPER CONVERGENT
PATTERN OVER THE AMERICAS IS LIMITING THE COVERAGE OF
PRECIPITATING CONVECTION IN EXTENSIVE PORTIONS OF THE
REGION...WITH A FEW ISOLATED EXCEPTIONS. THE DRYING IS MORE
NOTICEABLE IN MEXICO...WHICH LIES DOWNSTREAM OF A DRY AIR MASS
CURRENTLY PRESENT OVER THE GULF OF MEXICO...IN THE NORTHEAST
CARIBBEAN WHICH IS UNDER THE INFLUENCE OF A SAHARAN AIR
LAYER...AND IN SOUTHERN CENTRAL AMERICA/NORTHWEST COLOMBIA...WHERE
LIMITED AVAILABLE MOISTURE AND ACCELERATED TRADES ARE LIMITING
PRECIPITATION.
IN MEXICO...LIMITED AMOUNTS OF AVAILABLE MOISTURE ARE FORECAST TO
CONTINUE YIELDING TO BELOW-AVERAGE PRECIPITATION THROUGH THE
FORECAST CYCLE. MOST ACTIVITY IS FORECAST TO CLUSTER IN AREAS TO
THE SOUTH OF 21N...AND ALONG THE SIERRA MADRE OCCIDENTAL IN A MORE
ISOLATED MANNER. THROUGH THE FORECAST CYCLE...THE MOST SIGNIFICANT
SYSTEM IS A TROPICAL WAVE THAT IS INTERACTING WITH A TUTT OVER THE
GULF OF HONDURAS. THIS WILL FAVOR MAXIMA OF 20-40MM IN SOUTHERN
MEXICO AND MAXIMA OF 15-20MM IN THE YUCATAN PENINSULA ON
THURSDAY...AND ON FRIDAY WILL FAVOR MAXIMA OF 25-50MM IN
OAXACA/GUERRERO AND GENERALLY MAXIMA OF 20-35MM IN THE EJE
VOLCANICO TRANSVERSAL AND PORTIONS OF SOUTHERN VERACRUZ.
A TRADE WIND SURGE IS DISSIPATING ACROSS THE CENTRAL BAHAMAS ON
WEDNESDAY...AND ASSOCIATES WITH A ROBUST SAHARAN AIR LAYER BEHIND
IT. THE DUST EXTENDS AS FAR WEST AS THE CENTRAL BAHAMAS AND COVERS
HISPANIOLA...PUERTO RICO AND THE NORTHERN LESSER ANTILLES. AS THE
DRY AIR MASS CONTINUES PROPAGATING WESTWARD...EXPECT A DECREASING
TREND IN THE COVERAGE OF CONVECTION AND ACCUMULATIONS.
HOWEVER...THE INFLUENCE OF ENHANCED MOISTURE CONVERGENCE AHEAD OF
THE LEADING EDGE OF THE TRADE WIND SURGE WILL FAVOR MODERATE
CONVECTION IN THE NORTHWEST BAHAMAS ON WEDNESDAY...TO FAVOR MAXIMA
OF 15-20MM. IN WEST CUBA...AN EXITING TROPICAL WAVE INTERACTING
WITH THE AFOREMENTIONED TUTT WILL FAVOR MAXIMA OF 20-35MM ON
WEDNESDAY...AND DIURNAL THUNDERSTORMS WILL FAVOR MAXIMA OF 15-20MM
IN EAST CUBA. ON THURSDAY EXPECT MAXIMA OF 15-25MM IN CENTRAL AND
WESTERN CUBA...CAYMAN ISLANDS AND EASTERN JAMAICA. MUCH DRIER
CONDITIONS ARE EXPECTED ON FRIDAY.
IN CENTRAL AMERICA...ALBEIT THE DRY CONDITIONS...SOME ENHANCEMENT
WILL BE PROVIDED BY TROPICAL WAVES IN THE CARIBBEAN BASIN OF
NICARAGUA/HONDURAS ON WEDNESDAY...AND IN PANAMA AND SOUTHERN COSTA
RICA ON FRIDAY. YET...THE INFLUENCE OF THE STRONG EASTERLY TRADES
WILL CONTINUE TO LIMIT ACTIVITY IN THE PACIFIC BASIN. SEE TROPICAL
WAVE SECTION FOR RAINFALL AMOUNTS.
ACCELERATED EASTERLY FLOW IN THE MID-TROPOSPHERE OF NORTHERN SOUTH
AMERICA WILL CONTINUE TO FAVOR A DIPOLE IN PRECIPITATION ACROSS
COLOMBIA...WHERE EXPECT WET CONDITIONS IN THE ORINOQUIA AND MUCH
MORE ISOLATED PRECIPITATION WEST OF THE EASTERN ANDEAN RANGE. THIS
IS FORECAST TO GRADUALLY DECREASE THROUGH FRIDAY...WHICH WILL
FAVOR A GRADUAL INCREASE IN PRECIPITATION. THE LARGEST
ACCUMULATIONS ARE EXPECTED ON FRIDAY IN ASSOCIATION WITH A
TROPICAL WAVE...WHEN EXPECT 15-20MM/DAY AND MAXIMA OF 25-50MM.
OTHERWISE...EXPECT MODERATE CONVECTION IN NORTHEAST AND CENTRAL
VENEZUELA ON WEDNESDAY STIMULATED BY A TROPICAL WAVE...WHICH WILL
FAVOR MAXIMA OF 30-60MM. ON THURSDAY THIS WILL FAVOR MAXIMA OF
20-40MM IN THE ENTIRE ORINOQUIA...AND TRAILING MOISTURE WILL FAVOR
SIMILAR AMOUNTS IN CANAIMA IN SOUTHEAST VENEZUELA.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 20/00 20/12 21/00 21/12 22/00 22/12 23/00 23/12
TW 15N 61W 65W 68W 71W 73W 76W 78W 82W 84W
TW 24N 83W 86W 88W 91W 94W 97W 100W 102W 104W
TW 21N 98W 103W 107W 110W 114W EXITS
TW 22N 112W 115W 116W EXITS
A TROPICAL WAVE IS INITIALIZED AT 61W AND SOUTH OF 15N. ON
WEDNESDAY IT WILL FAVOR MAXIMA OF 30-60MM IN NORTH-CENTRAL
VENEZUELA AND MAXIMA OF 20-45MM ELSEWHERE IN VENEZUELA. ON
THURSDAY IT WILL FAVOR MAXIMA OF 20-40MM IN NORTHEAST COLOMBIA AND
CENTRAL VENEZUELA...WHILE FAVORING MAXIMA OF 15-25MM IN SOUTHERN
COLOMBIA. ON FRIDAY...IT WILL FAVOR MAXIMA OF 30-60MM FROM COSTA
RICA TO NORTHWEST COLOMBIA.
A TROPICAL WAVE IS INITIALIZED AT 83W AND SOUTH OF 24N. THE WAVE
IS TRAILED BY AN IMPORTANT SAHARAN AIR LAYER AND ASSOCIATED DRY
CONDITIONS. YET...THE WAVE IS INTERACTING WITH A TUTT LOW LOCATED
IN THE GULF OF HONDURAS ON WEDNESDAY. THIS WILL FAVOR MAXIMA OF
20-35MM IN WEST CUBA AND MAXIMA OF 20-40MM IN EASTERN
NICARAGUA/EAST HONDURAS ON WEDNESDAY. ON THURSDAY EXPECT MAXIMA OF
20-40MM FROM WESTERN HONDURAS/GUATEMALA/BELIZE INTO SOUTHERN
VERACRUZ. PORTIONS OF THE YUCATAN CAN EXPECT MAXIMA OF 15-20MM. ON
FRIDAY...THE WAVE WILL FAVOR MAXIMA OF 25-50MM IN GUERRERO AND
WEST OAXACA.
A TROPICAL WAVE IS INITIALIZED AT 98W AND SOUTH OF 21N. THIS WAVE
IS PROPAGATING VERY RAPIDLY...LIMITING ITS EFFECTS ON CONVECTION.
ON WEDNESDAY IT WILL FAVOR ISOLATED MAXIMA OF 15-25MM IN PORTION
OF NAYARIT/JALISCO/COLIMA...TO THEN EXIT TO THE OPEN WATERS OF THE
PACIFIC OCEAN. IT WILL HAVE LIMITED EFFECTS TO THE CONTINENT AND
EXITS THE FORECAST AREA BY FRIDAY.
A TROPICAL WAVE IS INITIALIZED AT 112W AND SOUTH OF 22N...AND WILL
HAVE LIMITED EFFECTS ON CONTINENTAL CONVECTION AND EXITS THE
FORECAST AREA BY THURSDAY.
GALVEZ/ACOSTA/ALAMO...WPC (USA)
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