892
FXUS02 KWBC 230659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT MON SEP 23 2024
VALID 12Z THU SEP 26 2024 - 12Z MON SEP 30 2024
...TROPICAL SYSTEM DEVELOPMENT THREAT FOR THE GULF OF MEXICO AND
CENTRAL TO EASTERN GULF COAST/SOUTHEAST MID-LATE WEEK...
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES SEEM TO BE FINALLY TRENDING TOWARDS A MORE
CONSISTENT FLOW PATTERN ACROSS THE CONUS DURING THE MEDIUM RANGE
PERIOD, WHICH INCLUDES THE EVENTUAL TRACK OF A POSSIBLE TROPICAL
SYSTEM THROUGH THE GULF OF MEXICO AND TOWARDS THE CENTRAL-EASTERN
GULF COAST REGION LATE THIS WEEK. MODELS HAVE TRENDED TOWARDS MORE
SPLITTING OF FLOW AND A CUTOFF UPPER LOW LINGERING OVER THE MIDDLE
MISSISSIPPI VALLEY MUCH OF THE PERIOD. THIS SHOULD HELP TO PULL A
GULF TROPICAL SYSTEM NORTHWARD AND FASTER THAN PREVIOUS GUIDANCE.
LATEST QPF/ERO FORECASTS FROM WPC AND NHC THOUGHTS REFLECTED THIS.
STILL, VERY LITTLE CONFIDENCE IN ANY OF THE SPECIFICS ASSOCIATED
WITH ESPECIALLY THE TROPICAL AND UNTIL AN ACTUAL SYSTEM FORMS,
MODELS WILL LIKELY CONTINUE TO FLIP-FLOP. SHOULD ALSO NOTE THAT THE
ENSEMBLE MEANS ARE A LITTLE SLOWER THAN THEIR DETERMINISTIC
COUNTERPARTS, WHICH HIGHLIGHTS THE UNCERTAINTIES IN INDIVIDUAL
ENSEMBLE MEMBERS. ELSEWHERE ACROSS THE CONUS, THERE IS SOME TIMING
AND AMPLITUDE UNCERTAINTY WITH ANOTHER SHORTWAVE INTO THE WESTERN
U.S. LATE WEEKEND AND REINFORCED TROUGHING/A CLOSED LOW NEAR THE
NORTHEAST.
THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM A
COMPOSITE BLEND OF THE GENERALLY COMPATIBLE GFS/ECMWF AND ECMWF
ENSEMBLE MEANS FOR THURSDAY INTO SATURDAY WHOSE FORECAST CLUSTER
WAS CLOSEST TO NHC THOUGHTS ON POTENTIAL GULF TROPICAL DEVELOPMENT
AND TRACK. AFTER THIS, FAVORED A SOLUTION CLOSEST TO THE EMSEMBLE
MEANS GIVEN INCREASING UNCERTAINTY. THIS PLAN IS OVERALL FASTER
THAN WPC CONTINUITY WITH THE GULF COAST SYSTEM AND FASTER TO BRING
COPIUS RAINFALL TO THE EAST-CENTRAL GULF COAST AND THE SOUTHEAST.
..WEATHER/HAZARDS HIGHLIGHTS
THE NATIONAL HURRICANE CENTER (NHC) AND THE WEATHER PREDICTION
CENTER AMONG OTHERS CONTINUE TO MONITOR POSSIBLE TROPICAL SYSTEM
FORMATION IN THE CARIBBEAN THAT LOOKS TO LIFT INTO THE GULF OF
MEXICO TO THREATEN MARITIME INTERESTS AND THE CENTRAL TO EASTERN
GULF COAST/SOUTHEAST MID-LATE WEEK. GIVEN THE SYSTEM HAS YET TO
FORM, STRENGTH AND TRACK REMAIN UNCERTAIN, BUT THE PICTURE US
GETTING CLEARER. THE VAST BULK OF RECENT GUIDANCE OFFERS A GROWING
SIGNAL FOR IMPACTFUL WEATHER, INCLUDING A THREAT FOR HEAVY
RAINFALL/WINDS/SURF FOR THE CENTRAL TO EASTERN GULF COAST/FLORIDA,
WITH IMPACTFUL WEATHER POSSIBLE THROUGH THE SOUTHEAST AND VICINITY
LATE WEEK INTO THE WEEKEND. THERE HAS BEEN AN OVERALL FASTER TREND
IN RECENT GUIDANCE. BY DAY 4/THURSDAY, THERE ARE EXPANSIVE WPC
MARGINAL AND SLIGHT RISK EXCESSIVE RAINFALL OUTLOOK (ERO) AREAS
SPREAD NORTHWARD ACROSS THE SOUTHEAST. IF THE CURRENT FORECAST
HOLD, IT IS LIKELY AT LEAST A MODERATE RISK WILL BE NEEDED CLOSER
TO THE COAST FOR THIS TIME PERIOD, BUT WITH ONGOING UNCERTAINTY, IT
STILL SEEMS PRUDENT TO HOLD OFF FOR NOW. REGARDLESS, LATEST MODELS
AND ENSEMBLES CONTINUE TO SUPPORT A HEAVY RAINFALL/STORM
SURGE/FLOODING THREAT ACROSS THE CENTRAL TO EASTERN GULF COAST
REGION BOTH WITH ADVANCE MOISTURE FEED INLAND AND WITH LANDFALL.
THE THREAT WOULD CONTINUE FOR DAY 5/FRIDAY WITH SYSTEM PROXIMITY
AND MOISTURE FEED BACK ACROSS THE SOUTHEAST AND INTO THE TENNESSEE
VALLEY/MID-SOUTH TO INTERCEPT A SLOW MOVING CLOSED LOW.
ELSEWHERE, UPPER TROUGH ENERGY WILL DIG THROUGH THE NORTHEAST MID-
LATE WEEK. A WAVY SURFACE FRONT WILL WORK OFFSHORE, LEADING TO
COASTAL LOW DEVELOPMENT AND EXIT. EXPECT A PERIOD OF ENHANCED RAIN
OVER MAINE THURSDAY WITH A CLOSED UPPER LOW AND WRAPBACK MOISTURE.
OUT WEST, MOST AREAS SHOULD BE DRY. THE WASHINGTON COASTAL RANGES
AND CASCADES WILL BE AN EXCEPTION WITH ENHANCED RAIN AND HIGHEST
ELEVATION SNOW POTENTIAL LATE WEEK WITH PACIFIC SYSTEM PASSAGES.
SCHICHTEL
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC MEDIUM
RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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