TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 PM EDT TUE JUL 16 2024

FORECAST BULLETIN 16 JUL 2024 AT 1830 UTC: A STRONG SURFACE HIGH
PRESSURE ACROSS THE CENTRAL ATLANTIC CONTINUES TO DOMINATE THE
ATLANTIC BASIN. THERE IS HOWEVER A WEAK SFC LOW PRESSURE
DEVELOPING ACROSS THE SOUTHERN CARIBBEAN...CLOSE TO PANAMA AND
COLOMBIA...AS WELL AS ANOTHER LOW PRESSURE ALONG THE MONSOON
TROUGH IN THE EAST PACIFIC. THE CENTRAL TO EASTERN TROPICAL
ATLANTIC IS FAIRLY QUIET AS A LARGE PLUME OF SAHARAN DUST AND DRY
AIR ENCOMPASSES MOST OF THE TROPICAL ATLANTIC...WITH THE EXCEPTION
OF AREAS ALONG THE ITCZ / MONSOON TROUGH. A SERIES OF TROPICAL
WAVES WILL BE MOVING THROUGH THE TROPICAL REGION OVER THE NEXT FEW
DAYS. THESE TROPICAL WAVES ARE PROVIDING LOCALLY HIGHER AREAS OF
MOISTURE...WHICH WILL HELP INCREASE THE CHANCES OF SHOWERS AS THEY
APPROACH LAND AREAS. IN THE UPPER LEVELS...A FEW TROUGHS AND LOW
PRESSURES ARE HELPING THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS
AS THEY REMAIN NEARLY STATIONARY FOR THE REST OF THE WORKWEEK.
THERE IS AN UPPER LOW ACROSS THE WESTERN TROPICAL ATLANTIC...EAST
OF THE BAHAMAS...AND ANOTHER OVER EASTERN TEXAS. THESE UPPER LOWS
WOULD CAUSE RISING MOTION JUST NORTH OF THE CARIBBEAN AND OVER
NORTHEASTERN MEXICO RESPECTIVELY. AN UPPER TROUGH OVER THE CENTRAL
CARIBBEAN IS EXPECTED TO WEAKEN OVER THE NEXT FEW DAYS...AND ITS
LIMITED IMPACT COULD CAUSE MODEST AMOUNTS OF SHOWERS OVER CENTRAL
AMERICA.

IN TERMS OF RAINFALL ACCUMULATIONS...SOME SECTIONS OF NORTHERN
SOUTH AMERICA WOULD HAVE SIGNIFICANT RAINFALL...THOUGH DIFFERENT
SECTIONS EACH DAY THROUGH THE END OF THE WORKWEEK. THESE LOCAL
MAXIMUM RAINFALL COULD BE ATTRIBUTED TO THE INTERACTION BETWEEN
TROPICAL WAVES WITH THE LOCAL TERRAIN AND AVAILABLE MOISTURE. THIS
IS BECAUSE THE MID AND UPPER LEVEL DYNAMICS ARE NOT PARTICULARLY
CONDUCIVE FOR PROLONGED RISING MOTION OR VENTILATION...AS THE
WINDS ARE LIGHT. THAT SAID...THE WESTERN SECTIONS OF COLOMBIA WILL
HAVE SIGNIFICANT RAINFALL TODAY AND WEDNESDAY INTO THURSDAY...AS A
LOW PRESSURE AT THE SURFACE BRINGS PERSISTENT DEEP MOISTURE FROM
THE MONSOON TROUGH INTO THE CONTINENT. THE RAINFALL FORECAST FOR
WESTERN COLOMBIA SUGGESTS DAILY ACCUMULATIONS IN THE ORDER OF
15-20MM/DAY WITH MAX VALUES RANGING FROM 35 TO 80MM TODAY AND
WEDNESDAY. THURSDAY INTO FRIDAY COULD BE A BIT DRIER...AND THE
FORECAST FOR WESTERN COLOMBIA HAS MAX VALUES BETWEEN 20-35MM BUT
NORTHERN COLOMBIA COULD OBSERVE UP TO 60MM...THOUGH THIS COULD BE
DUE TO THE PASSING OF A TROPICAL WAVE. FOR THE REST OF NORTHERN
SOUTH AMERICA...MOISTURE POOLING ASSOCIATED WITH A TROPICAL WAVE
COULD CAUSE AS MUCH AS 50-100MM OF RAIN ACROSS EASTERN VENEZUELA
AND NORTHERN BRAZIL TODAY. HOWEVER...THIS IS A COMPROMISE AS THE
GFS MODEL IS VERY AGGRESSIVE WITH THE AMOUNTS...SUGGESTING HIGHER
THAN 125MM...WHILE THE ECMWF IS VERY SHY WITH THE RAINFALL
SOLUTION. GIVEN THE CURRENT SATELLITE IMAGERY...BEING CLOSER TO
THAT GFS SOLUTION...WE DECIDED TO LEAN TOWARDS THE GFS BUT WITH
SLIGHTLY LOWER AMOUNTS. OTHER AREAS IN VENEZUELA AND THE GUIANAS
ARE FORECAST TO OBSERVE UNDER 25MM OF RAIN TODAY. ON
WEDNESDAY...PORTIONS OF CENTRAL VENEZUELA TO THE SOUTH INTO
NORTHERN BRAZIL ARE FORECAST TO OBSERVE RAINFALL MAXIMA BETWEEN
20-60MM...WITH CENTRAL VENEZUELA ON THE HIGHER END OF THAT RANGE.
OTHER SECTIONS OF NORTHERN SOUTH AMERICA...INCLUDING THE
GUIANAS....EASTERN AND NORTHERN COLOMBIA...AS WELL AS NORTHERN
VENEZUELA...ARE FORECAST TO OBSERVE AMOUNTS GENERALLY BETWEEN
05-10MM WITH MAXIMA BETWEEN 15-35MM ON WEDNESDAY. ON THURSDAY INTO
FRIDAY...NORTHEASTERN VENEZUELA AND NORTHWESTERN GUYANA...AS WELL
AS NORTHERN COLOMBIA AND WESTERN VENEZUELA...COULD OBSERVE
RAINFALL MAXIMA BETWEEN 30 AND 80MM...THOUGH ELSEWHERE IN THE
REGION...35MM OR LESS CAN BE EXPECTED.

ACROSS MEXICO...A LARGE PART OF THE COUNTRY WILL OBSERVE RAINFALL
EACH DAY THROUGH THE REST OF THE WORKWEEK...ESPECIALLY ALONG
SIERRA MADRE. THERE IS AN INCREASE IN MOISTURE AS A TROPICAL WAVE
PASSES JUST SOUTH OF THE COUNTRY...AND A SFC HIGH PRESSURE PUSHES
ONSHORE FLOW INTO THE WEST COAST. THIS WILL COMBINE WITH A
PREDOMINANTLY EASTERLY WIND FLOW FROM THE GULF...CAUSING A
PERSISTENT MOISTURE CONVERGENCE ACROSS THE HIGHER ELEVATIONS. THIS
LOW LEVEL CONVERGENCE WILL COMBINE WITH AN UPPER TROUGH ACROSS
TEXAS...WHICH WILL GIVE RISING MOTION ACROSS THE SOUTH AND AND
SOUTHEAST OF THE UPPER LOW...WHICH IS OVER PORTIONS OF CENTRAL
MEXICO. THEREFORE...DAILY RAIN VALUES BETWEEN 05-15MM WITH
LOCALIZED MAXIMA BETWEEN 20-45MM CAN BE EXPECTED ACROSS MANY
SECTORS OF MEXICO THROUGH THE END OF THE WORKWEEK.

THE RAINFALL AMOUNTS ACROSS THE CARIBBEAN ISLANDS AND MOST OF
CENTRAL AMERICA IS A BIT MORE MODEST THAN THE REST OF THE TROPICAL
REGION. WITH THE EXCEPTION OF THE EASTERNMOST SECTIONS OF
PANAMA...WHICH COULD OBSERVE SIGNIFICANT RAIN ASSOCIATED WITH THE
SFC LOW AND MONSOON TROUGH...THE REST OF CENTRAL AMERICA IS
FORECAST TO OBSERVE DAILY RAINFALL VALUES NEAR 05-10MM WITH MAXIMA
BETWEEN 15-35MM FOR THE REST OF THE WORKWEEK. WHILE THE CARIBBEAN
ISLANDS COLD EXPECT EVEN LOWER AMOUNTS...OBSERVING DAILY RAINFALL
OF AROUND 05-10MM OR LESS...WHILE ISOLATED MAXIMA OF 25MM OR LESS
IS POSSIBLE. THAT SAID...SAHARAN DUST IS EXPECTED TO MOVE INTO THE
CARIBBEAN FROM WEDNESDAY NIGHT ONWARD...WHICH WILL BRING DRIER AIR
AND EVEN LESS SHOWER ACTIVITY.


ALAMO...(WPC)
FERNANDER...(BDM)
CLARKE...(CINWS)