TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
352 PM EDT WED SEP 11 2024

FORECAST BULLETIN 12 SEPT 2024 AT 1945 UTC:

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON HURRICANE
FRANCINE...WHICH IS FORECAST TO MAKE LANDFALL IN THE LOUISIANA
COAST THIS EVENING. THE RAINFALL ASSOCIATED WITH FRANCINE IS NO
LONGER EXPECTED TO AFFECT NORTHEAST TAMAULIPAS...AS THE HURRICANE
IS NOW FAR ENOUGH FROM NORTHEASTERN MEXICO. THERE IS ALSO A NEW
TROPICAL DEPRESSION SEVEN...LOCATED AT 16.0N AND 28.7W. THIS
TROPICAL DEPRESSION IS FORECAST TO MOVE WEST TO WEST NORTHWEST FOR
THE NEXT SEVERAL DAYS...AND REMAIN OVER THE OPEN WATERS.

ACROSS THE ATLANTIC BASIN...THERE ARE A FEW LOW PRESSURES ALONG
THE MONSOON TROUGH..WHICH ARE MOVING WEST. ONE OF THE LOW
PRESSURES IS LOCATED NEAR 13N/54W AND 13N/46W. THE LATEST MODEL
GUIDANCE IS SUGGESTING THAT THE LOW PRESSURES NEAR 54W AND 46W
WILL BE MOVING SLOWLY TO THE WEST...AS THEY WEAKEN. THEY ARE
FORECAST TO BECOME A TROUGH BY THE END OF THE WORKWEEK...AS THEY
APPROACH THE NORTHERN LEEWARD ISLANDS. A TROPICAL WAVE NEAR 85W
WILL CONTINUE TO MOVE WEST...ENHANCING THE CHANCES OF SHOWER
ACTIVITY OVER THE NEXT FEW DAYS OVER CENTRAL AMERICA TO THE EAST
OF ITS AXIS.

AT THE SURFACE...OTHER THAN THE AFOREMENTIONED LOW PRESSURES ALONG
THE MONSOON TROUGH IN THE ATLANTIC...THERE IS A BROAD HIGH
PRESSURE ACROSS THE NORTHEASTERN ATLANTIC...AS WELL AS A HIGH
PRESSURE ENTERING THE NORTHWESTERN ATLANTIC. THIS WILL CAUSE A
PREVAILING EASTERLY TO SOUTHEASTERLY WIND FLOW ACROSS THE TROPICAL
ATLANTIC INTO THE CARIBBEAN. THE WIND FLOW OVER THE GULF OF MEXICO
WILL BE STRONGLY INFLUENCED BY HURRICANE FRANCINE...WITH WINDS
BEING GENERALLY FROM THE SOUTH TO SOUTHWEST TODAY INTO
FRIDAY...BUT BECOMING LIGHTER WITH EACH PASSING DAY.

IN THE MID LEVELS...THERE IS A LOW PRESSURE OVER THE CENTRAL
ATLANTIC...WHICH WILL WEAKEN BY THURSDAY AFTERNOON INTO A MID
LEVEL TROUGH. ANOTHER TROUGH IS PRESENT OVER THE WEST TROPICAL
ATLANTIC...JUST NORTH OF PUERTO RICO/USVI...WHICH WILL WEAKEN AND
FLATTEN BY THIS EVENING INTO EARLY THURSDAY. A BROAD HIGH PRESSURE
IS LOCATED AND WILL PERSIST OVER THE BAHAMAS INTO THE GULF OF
MEXICO THROUGH FRIDAY. A WEAK MID LEVEL TROUGH OVER MEXICO WILL
FLATTEN AND LIFT BY THURSDAY...THEN A TROUGH WILL DEVELOP OVER
NORTHWESTERN MEXICO AND THE BAJA PENINSULA...WHILE A MID LEVEL
HIGH PRESSURE WILL PERSIST OVER CENTRAL MEXICO.

THE UPPER LEVELS WILL HAVE SIMILAR FEATURES TO THE MID LEVELS.
THERE IS A HIGH PRESSURE OVER CENTRAL MEXICO...THAT WILL EXTEND
EAST INTO THE GULF OF MEXICO. A COUPLE OF UPPER HIGH PRESSURES ARE
ALSO LOCATED ACROSS THE CENTRAL TO EASTERN TROPICAL ATLANTIC. A
NARROW UPPER TROUGH HAS ITS AXIS OVER THE WESTERN TROPICAL
ATLANTIC...NORTH OF PUERTO RICO. THIS GENERAL PATTERN COULD
PROMOTE SOME STABILITY OR AT LEAST KEEP DEEP VERTICAL DEVELOPMENT
FROM OCCURRING.

THE AREA WITH HIGHEST RAINFALL POTENTIAL OVER THE NEXT THREE DAYS
WILL BE PORTIONS OF WESTERN MEXICO...ESPECIALLY FROM JALISCO TO
SINALOA...AS WELL AS THE SOUTHERN BAJA CALIFORNIA PENINSULA. THIS
IS DUE TO A DEVELOPING LOW PRESSURE...WHICH CURRENTLY HAS A HIGH
CHANCE OF TROPICAL CYCLONE FORMATION ACCORDING TO THE NATIONAL
HURRICANE CENTER. THIS DEVELOPING LOW PRESSURE WILL BRING MOISTURE
TO THE WEST COAST OF MEXICO AND THE SOUTHERN BAJA CALIFORNIA
PENINSULA OVER THE NEXT FEW DAYS REGARDLESS OF DEVELOPMENT. THIS
MOISTURE ADVECTION AND ONSHORE WINDS FROM VERY WARM WATERS...WILL
CAUSE SHOWER AND THUNDERSTORM DEVELOPMENT WHEN IT COMBINES WITH
THE LOCAL OROGRAPHIC EFFECTS. THE MODEL GUIDANCE APPEARS TO BE A
BIT SHY WITH THE RAINFALL AMOUNT SOLUTION...AND THUS OUR FORECAST
SUGGESTS HIGHER RAINFALL AMOUNTS THAN THE MODEL GUIDANCE IS
SUGGESTING...CONSIDERING HOW WARM THE WATERS ARE AND HOW MUCH
MOISTURE WILL BE MOVING INTO WESTERN MEXICO INTERACTING WITH THE
LOCAL TERRAIN. AT THIS TIME...THE RAINFALL TOTALS BEING FORECAST
COULD HAVE 3-DAY MAX VALUES FROM AROUND 100 TO 200MM OR SO. SOME
SECTIONS OD SOUTHWESTERN SONORA COULD OBSERVE SIGNIFICANT
RAIN...BUT MOST OF ITS RAIN WOULD BE OBSERVED FROM FRIDAY INTO
SATURDAY...WITH MAX VALUES NEAR 30-50MM.

ELSEWHERE ACROSS THE REGION...THE DAILY RAINFALL ACCUMULATIONS
WILL BE GENERALLY IN THE ORDER OF 05-15MM/DAY WITH MAX VALUES
BETWEEN 20 AND 45MM/DAY OVER THE NEXT 3 DAYS. A FEW FACTORS WILL
PLAY A ROLE ON WHERE AND WHEN WILL THE RAINFALL AFFECT THE
DIFFERENT AREAS. SURFACE TROUGHS WILL CAUSE MAX DAILY VALUES UP TO
35MM OVER NORTHERN SOUTH AMERICA EACH DAY...WHILE AREAS NOT BEING
AFFECTED BY A SFC TROUGH ARE FORECAST MAX VALUES NEAR 25MM.
SOUTHERN CENTRAL AMERICA WILL OBSERVE PERSISTENT RAINFALL WITH MAX
VALUES NEAR 20-35MM AS THE ITCZ IS PASSING THROUGH THE
AREA...CAUSING HIGHER THAN NORMAL MOISTURE FOR THE NEXT 3 DAYS.
MEANWHILE...PORTIONS OF NICARAGUA AND HONDURAS WILL HAVE A DRY
SLOT MOVE IN AND THEREFORE OBSERVE LITTLE TO NO RAIN. THE
CARIBBEAN REGION WILL HAVE SCATTERED SHOWERS EACH DAY. THE
COMBINATION OF THE AVAILABLE MOISTURE AND LOCAL EFFECTS WILL CAUSE
DIURNAL SHOWERS AND THUNDERSTORMS OVER AREAS OF LOW LEVEL
CONVERGENCE...PARTICULARLY ACROSS THE HIGHER ELEVATIONS.


ALAMO...(WPC)