TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
214 PM EDT MON JUL 22 2024

FORECAST BULLETIN 22 JUL 2024 AT 1815 UTC: A RELATIVELY DENSE
SAHARAN DUST LAYER (SAL) IS AFFECTING PORTIONS OF THE CENTRAL
CARIBBEAN...THE BAHAMAS...AND CENTRAL AMERICA INTO MEXICO TODAY.
THERE IS ALSO SOME SAHARAN DUST AFFECTING THE NORTHERNMOST
SECTIONS OF SOUTH AMERICA...MOSTLY AFFECTING NORTHERN VENEZUELA
AND ADJACENT AREAS OF THE NORTHERN COAST. THE SAL OVER THE
CARIBBEAN REGION IS EXPECTED TO MOVE WEST NORTHWEST OVER THE NEXT
FEW DAYS. THIS WILL CAUSE CLEANER AIR TO MOVE INTO THE CARIBBEAN
REGION OVER THE NEXT FEW DAYS...BUT PORTIONS OF THE YUCATAN
PENINSULA INTO THE GULF OF MEXICO WILL SEE AN INCREASE IN THE SAL
INTO WEDNESDAY. ANOTHER RELATIVELY DENSE SAL IS MOVING THROUGH THE
TROPICAL ATLANTIC...AND THIS OTHER PLUME OF SAHARAN DUST WILL
START REACHING THE LESSER ANTILLES LATE WEDNESDAY. ACCORDING TO
THE LATEST GUIDANCE...THE CONCENTRATION OF THIS NEXT SAL EVENT
COULD BE SIMILAR TO THE ONE RECENTLY OBSERVED. THEREFORE...THERE
IS DRIER THAN NORMAL AIR OVER THE CARIBBEAN...WHICH IS MOVING WEST
NORTHWEST AND WILL AFFECT PORTIONS OF CENTRAL AMERICA...MAINLY
FROM NICARAGUA NORTHWARD...INTO THE YUCATAN PENINSULA OVER THE
NEXT COUPLE OF DAYS. THAT BEING SAID...MOISTURE WILL INCREASE
ACROSS THE SOUTHERN CARIBBEAN BY WEDNESDAY...AND WILL PROPAGATE
WEST NORTHWEST AS A SFC LOW OVER THE SOUTHWESTERN CARIBBEAN PULLS
MOISTURE FROM THE ITCZ. DRIER AIR WILL ALSO MOVE IN TO THE LESSER
ANTILLES LATE WEDNESDAY INTO THURSDAY WITH THE NEXT SAL
EVENT...WHICH WILL MOVE IN WITH A TRADE WIND SURGE BEHIND A
TROPICAL WAVE.

ACCORDING TO THE NATIONAL HURRICANE CENTER...THERE IS NO CYCLONE
ACTIVITY EXPECTED OVER THE NEXT 7 DAYS ACROSS THE ATLANTIC BASIN.
HOWEVER...THERE ARE A COUPLE OF DISTURBANCES IN THE EAST PACIFIC
THAT THE NATIONAL HURRICANE CENTER IS MONITORING FOR POSSIBLE
TROPICAL CYCLONE FORMATION. ONE IS A TROPICAL WAVE AT AROUND 102W
AND ANOTHER NEAR 114W...BOTH OF WHICH HAVE A LOW CHANCE OF
TROPICAL CYCLONE FORMATION IN 7 DAYS WITH A PROBABILITY OF 10
PERCENT AND 30 PERCENT RESPECTIVELY. THE GFS MODEL GUIDANCE
SUGGESTS THE DEVELOPMENT OF A LOW PRESSURE FOR THE WAVE NEAR 114W 
BY WEDNESDAY...BUT THE ECMWF DOES NOT LIKE IT AS MUCH. REGARDLESS
OF DEVELOPMENT...BOTH OF THESE DISTURBANCES ARE FORECAST TO
CONTINUE MOVING WEST AND INTO OPEN WATERS. 

AT THE SURFACE...A STRONG HIGH PRESSURE CONTINUES TO DOMINATE THE
ATLANTIC...CAUSING EASTERLY TO SOUTHEASTERLY WINDS ACROSS THE
ATLANTIC...CARIBBEAN AND INTO THE GULF OF MEXICO. THERE IS ALSO A
SFC LOW SOUTH OF PANAMA IN THE EAST PACIFIC...WHICH WILL BE
ABSORBED BY ANOTHER SFC LOW PRESSURE MOVING INTO THE SOUTH
CARIBBEAN FROM NORTHERN SOUTH AMERICA ON TUESDAY. THIS IS CAUSING
A TIGHTENING OF THE PRESSURE GRADIENT ACROSS THE CARIBBEAN SEA AND
THEREFORE LOCALLY STRONGER WINDS. THIS SFC LOW WILL MEANDER OVER
THE AREA FOR THE NEXT FEW DAYS...NOT ONLY CAUSING PERSISTENT
LOCALLY STRONGER WINDS OVER THE CARIBBEAN...BUT ALSO CAUSING
MOISTURE CONVERGENCE OVER COSTA RICA AND PANAMA.

THE UPPER LEVELS ARE PROVIDING SOME SUPPORT FOR CONVECTION ACROSS
THE WESTERN GULF OF MEXICO AND INTO PORTIONS OF MEXICO. THIS IS
DUE TO AN UPPER LOW OVER NORTHEASTERN MEXICO COMBINING WITH DEEP
MOISTURE OVER THE AREA. THIS UPPER LOW WILL WEAKEN BY
TUESDAY...BUT IT WILL BE ABSORBED BY A LARGER UPPER TROUGH
DOMINATING MOST OF THE CENTRAL U.S. INTO NORTHEASTERN MEXICO.
THERE IS ANOTHER UPPER LOW...THIS ONE ACROSS THE WESTERN TROPICAL
ATLANTIC JUST EAST OF THE BAHAMAS...BUT THE AIR IS VERY DRY OVER
THAT AREA...AND THEREFORE THE CONVECTION IS LIMITED.

THE LOW TO MID LEVEL RELATIVE HUMIDITY ACROSS THE TROPICAL REGION
SHOWS THAT THE MOISTURE ALONG THE ITCZ INTO MEXICO AND THE GULF OF
MEXICO WILL PERSIST FOR THE NEXT FEW DAYS...WITH THE EXCEPTION OF
THE DRIER AIR WITH SAHARAN DUST MOVING INTO THE YUCATAN PENINSULA
BY TUESDAY. THIS DEEPER MOISTURE WILL COMBINE WITH THE
AFOREMENTIONED UPPER TROUGH ACROSS MEXICO TO CAUSE PERSISTENT
SHOWER ACTIVITY OVER MANY SECTORS OF CENTRAL TO SOUTHERN MEXICO
OVER THE NEXT FEW DAYS. EVEN THOUGH THE SIERRA MADRE OCCIDENTAL IN
MEXICO IS ON THE CONVERGENT SIDE OF THE UPPER TROUGH...THE LOW
LEVEL WIND FLOW WILL BE FROM THE EASTERN PACIFIC INTO THE SIERRA
MADRE OCCIDENTAL...WHICH WILL PROVIDE MOISTURE TO MOVE INLAND AND
SHOWER ACTIVITY IS EXPECTED TO DEVELOP DUE TO OROGRAPHIC LIFTING.
THEREFORE...THE COMBINATION OF FACTORS WILL CAUSE MANY SECTORS IN
MEXICO TO OBSERVE RAINFALL OVER THE NEXT FEW DAYS.

ACROSS CENTRAL AMERICA...THE LOCATIONS WITH MOST PRECIPITATION ARE
EXPECTED TO BE AREAS IN AND AROUND COSTA RICA AND PANAMA...DUE TO
THE AFOREMENTIONED SFC LOW PRESSURE AND PERSISTENT DEEP MOISTURE
OVER THE AREA. NORTHWESTERN COLOMBIA WILL ALSO HAVE SIMILAR
AMOUNTS OF RAIN OVER THE 3-DAY FORECAST PERIOD. THE GLOBAL MODEL
GUIDANCE DIFFERS ON THE AMOUNTS OF RAIN...WITH THE GFS BEING MORE
AGGRESSIVE. HOWEVER...GIVEN THE RECENT SATELLITE IMAGERY AND MODEL
INITIALIZATION...THE GFS MODEL SEEMS TO HAVE A BETTER HANDLE ON
THE IMPACTS AND THEREFORE IT WILL NOT BE OUT OF THE REALM OF
POSSIBILITIES TO HAVE AROUND 50MM OR MORE OF RAIN IN LOCALIZED
AREAS FOR A 3-DAY RAINFALL TOTAL. ACROSS NORTHERN SOUTH
AMERICA...ANOTHER SECTOR TO OBSERVE IS THE CENTRAL TO EASTERN
SECTIONS OF VENEZUELA...WHICH IS EXPECTED TO HAVE A LOCALIZED
MAXIMUM OF RAIN OVER NORTHERN SOUTH AMERICA. ALTHOUGH THE MID TO
UPPER LEVELS ARE NOT PARTICULARLY PROVIDING SUPPORT FOR
CONVECTION...THE LOW LEVEL WINDS AND DEEP MOISTURE WILL COMBINE
WITH THE OROGRAPHIC LIFTING OVER THE AREA TO CAUSE DAILY SHOWERS
AND THUNDERSTORMS. ACROSS THE CARIBBEAN ISLANDS AND INTO THE
BAHAMAS...GIVEN THE DRIER THAN NORMAL AIR OVER THE AREA...THE AREA
IS EXPECTED TO OBSERVE MODEST AMOUNTS OF RAIN. THE GLOBAL MODEL
GUIDANCE IS SUGGESTING MAX VALUES OF ABOUT 50MM OVER VERY ISOLATED
AREAS FOR A 3-DAY TOTAL PRECIPITATION TOTALS...BUT MOST AREAS
COULD OBSERVE A 3-DAY MAX AMOUNT OF AROUND 35-40MM. THIS COULD
MEAN DAILY MAX VALUES OF UNDER 25MM ACROSS THE ISLANDS THROUGH
WEDNESDAY. THAT BEING SAID...THERE IS A MARGINAL RISK FOR STRONG
THUNDERSTORMS AND SQUALLY WEATHER ACROSS PORTIONS OF SOUTHERN
CUBA..SOUTHERN BAHAMAS AND THE TURKS AND CAICOS ON WEDNESDAY INTO
THURSDAY MORNING.



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