409
FXCA20 KWBC 091419
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1019 AM EDT FRI OCT 09 2026
FORECAST BULLETIN 09 OCTOBER 2026 AT 1400 UTC:
A WEAK TROPICAL WAVE IS CONTINUING TO MOVE ACROSS JAMAICA AND CUBA
TODAY, STILL SUPPORTING THE DEVELOPMENT OF ISOLATED CONVECTION.
ADDITIONALLY, A WESTWARD MOVING UPPER LEVEL TROUGH IS FAVORING
UPPER DIVERGENCE AND IN TURN, VENTILATION FOR CONVECTION FOR
TODAY. THESE CONDITIONS WILL FAVOR THE DEVELOPMENT OF CONVECTION
THROUGH THE DAY FRIDAY ACROSS JAMAICA AND CUBA. BY SATURDAY, THE
REMNANTS OF THE TROPICAL WAVE AND THE UPPER LEVEL TROUGH WILL MOVE
INTO THE NORTHWEST CARIBBEAN SEA, INCREASING MOISTURE ADVECTION
INTO HONDURAS AND NICARAGUA. ON SUNDAY, BOTH FEATURES WILL BE
ENTERING INTO THE YUCATAN PENINSULA, BELIZE, AND GUATEMALA. WITH
THE PASSAGE OF THESE FEATURES, EXPECT DAILY TOTAL PRECIPITATION
MAXIMA TO RANGE FROM 25 TO 30MM.
ANOTHER FEATURE OF INTEREST IN THE CARIBBEAN IS AN INCOMING LOW
LEVEL TROUGH THAT IS GOING TO ENTER INTO THE LEEWARD ISLANDS AND
PUERTO RICO/VIRGIN ISLANDS ON FRIDAY EVENING/EARLY SATURDAY
MORNING. THIS LOW LEVEL TROUGH WILL BE PROPAGATING ACROSS
HISPANIOLA ON SATURDAY AND EXITING INTO JAMAICA AND SOUTHEAST CUBA
FOR SUNDAY. THE SHARP INCREASE IN PRECIPITABLE WATER VALUES WILL
ALSO HELP INITIATE CONVECTION ACROSS THE REGION FOR THE NEXT THREE
DAYS, WHERE MODERATE TOTAL PRECIPITATION MAXIMA (REACHING 15MM) IS
LIKELY. NOTE THAT THIS LOW LEVEL TROUGH WILL HAVE A FAST
PROPAGATION SPEED, LIMITING THE RAINFALL ACCUMULATIONS.
ACROSS THE WINDWARD AND SOUTH LEEWARD ISLANDS, EXPECT MOSTLY
SEASONAL CONDITIONS FOR FRIDAY. THE PRESENCE OF A LONG FETCH
MOISTURE PLUME ACROSS THE WINDWARD ISLANDS WILL SUPPORT LOCALIZED
SHOWERS AND THUNDERSTORMS FOR FRIDAY. STARTING SATURDAY, THE AXIS
OF A WELL DEFINED WEST PROPAGATING MID-TO-UPPER LEVEL TROUGH WILL
ALSO BE MOVING INTO THE WEST CARIBBEAN, SUPPORTING THE SUBTLE
INCREASE IN MOISTURE AND INSTABILITY ACROSS THE REGION. RAINFALL
IMPACTS ARE EXPECTED TO INCREASE FOR SATURDAY AND CONTINUE INTO
SUNDAY, LEADING TO TOTAL PRECIPITATION MAXIMA OF UP TO 20MM IN
BARBADOS ON SATURDAY AND UP TO 20MM ACROSS THE REST OF THE
WINDWARD ISLANDS FOR SUNDAY.
IN CENTRAL AMERICA, THE SURFACE TO LOW LEVEL MONSOON TROUGH WILL
CONTINUE TO MEANDER IN THE REGION FOR THE NEXT THREE DAYS.
ISOLATED CONVECTION IS EXPECTED TO DEVELOP THROUGH SATURDAY. THERE
WILL BE A SLIGHT DECREASE IN MID-LEVEL MOISTURE FOR SUNDAY AS A
DRIER AIR MASS MOVES OVERHEAD. OVERALL, ANTICIPATE ISOLATED DAILY
TOTAL PRECIPITATION MAXIMA OF UP TO 40MM IN THE HIGHER TERRAIN
(ISOLATED) AND LESSER AMOUNTS IN THE LOWER ELEVATIONS.
ALONG THE PACIFIC COAST OF COLOMBIA AND ECUADOR, ANTICIPATE THE
DAILY DEVELOPMENT OF SHOWERS AND THUNDERSTORMS THAT WILL BE DRIVEN
BY DIURNAL CYCLE PROCESSES. SOUTHERLY LOW LEVEL WINDS AT 850 HPA
WILL ALSO HELP TRANSPORT A MOIST AIRMASS INTO THE CENTRAL AND
SOUTHERN COAST OF ECUADOR FOR FRIDAY, ELEVATING PRECIPITATION
CHANCES AND TOTAL PRECIPITATION MAXIMA. THEREAFTER, THE HIGHEST
TOTAL PRECIPITATION MAXIMA WILL BE TOWARDS THE NORTH-CENTRAL COAST
OF ECUADOR. ADDITIONALLY FOR SATURDAY AND SUNDAY, AT 850 HPA,
EXPECT ONSHORE WESTERLY LOW LEVEL WINDS TO DOMINATE IN THE REGION.
THIS PATTERN WILL FAVOR THE TRANSPORT OF TROPICAL AIR FROM THE
PACIFIC OCEAN AND SUPPORT ENHANCED TOTAL PRECIPITATION MAXIMA.
IN MEXICO, REMNANT MOISTURE PLUMES, INDIRECTLY ASSOCIATED WITH
HURRICANE ISAIAS, ARE CONTINUING TO CONVERGE INTO THE SOUTHERN
GULF REGION. AT THE SAME TIME, THERE WILL BE SPEED DIVERGENCE IN
THE REGION THAT WILL SUPPORT CONVECTIVE VENTILATION. THUS, EXPECT
MODERATE TOTAL PRECIPITATION MAXIMA ACROSS CHIAPAS, TABASCO, AND
PARTS OF GUATEMALA FOR TODAY AND SATURDAY. THERE WILL BE A CHANGE
IN THE DIRECTION OF THE LOW LEVEL WIND FLOW FOR SUNDAY THAT WILL
TRANSPORT DRIER AIR INTO THE AREA AND THUS DECREASING TOTAL
PRECIPITATION MAXIMA.
ANOTHER REGION OF INTEREST IS THE WEST PACIFIC COAST OF MEXICO,
SPECIFICALLY GUERRERO, MICHOACAN, COLIMA AND JALISCO, SINALOA, AND
NAYARIT FOR THE NEXT THREE DAYS. HURRICANE SIMON WILL BE MOVING
NEAR THE CONTINENT ON SATURDAY AND SUNDAY BUT IN ITS PERIPHERY,
THERE WILL BE FEEDER BANDS DEVELOPING. THESE FEEDER BANDS ARE
ANTICIPATED TO CONVERGE INTO GUERRERO ON FRIDAY AND INTO MICHOACAN
THROUGH THE FORECAST CYCLE. TOTAL PRECIPITATION MAXIMA IS LIKELY
TO EXCEED 500MM ACROSS MICHOACAN AS THE HURRICANE MOVES INTO THE
REGION. ACROSS GUERRERO, WEAKER FEEDER BANDS WILL CONVERGE INTO
THE AREA AND WILL SUPPORT TOTAL PRECIPITATION MAXIMA OF UP TO
100MM THROUGH MONDAY MORNING.
PRECIPITATION EFFECTS WILL INCREASE FOR SATURDAY AND SUNDAY IN
JALISCO AND COLIMA, WHERE A CUMULATIVE TOTAL PRECIPITATION MAXIMA
OF 400 TO 500MM IS LIKELY FOR THAT TIME PERIOD. IN PARTICULAR,
EXPECT PRECIPITATION TO INCREASE IN MAGNITUDE SATURDAY EVENING.
THE SYSTEM WILL BE MOVING PARALLEL TO THE NAYARIT AND SINALOA
COAST FOR SUNDAY AND TOTAL PRECIPITATION MAXIMA WILL BE FROM 100
TO 150MM THROUGH MONDAY MORNING.
ANOTHER REGION OF INTEREST IS NORTHERN BAJA CALIFORNIA WHERE
TROPICAL STORM RACHEL IS EXPECTED TO MOVE INTO FOR SATURDAY. A
MID-TO-UPPER LEVEL TROUGH WILL ABSORB RACHEL AS THE SYSTEM MOVES
INTO BAJA CALIFORNIA BUT ADDITIONAL VORTICITY MAXIMA AT 500 HPA
WILL FAVOR ASCENT AND THUS THE DEVELOPMENT OF CONVECTION IN THIS
REGION. ADDITIONALLY, EXPECT AN INCREASE IN CONVECTION ACROSS THE
MOUNTAINS OF SONORA AND SINALOA DUE TO THE INCREASE IN MOISTURE
AND INSTABILITY BEING SUPPORTED BY APPROACH OF THESE TWO TROPICAL
FEATURES AND THEIR COUPLING WITH THE DYNAMIC MID-LATITUDE
MID-TO-UPPER LEVELS, SPECIALLY FOR SATURDAY AND SUNDAY.
TROPICAL WAVES INITIALIZED AT 12 UTC:
TYPE SOF INIT 10/00 10/12 11/00 11/12 12/00 12/12 13/00 13/12
TW 16N 35W 37W 39W 41W 43W 45W 46W 48W 50W
TW 20N 78W 80W 82W 84W 86W 88W 90W 92W 94W
TINOCO-MORALES...(WPC)
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