569
FXUS02 KWBC 051915
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
315 PM EDT Sat Oct 5 2024

Valid 12Z Tue Oct 08 2024 - 12Z Sat Oct 12 2024


...What is forecast to become Hurricane Milton will cause
wind/surge and heavy rainfall threats across Florida Tuesday-
Wednesday...


...Overview...

Tropical Storm Milton has formed in the southwestern Gulf of
Mexico and is forecast to track east-northeast across the Gulf
while strengthening to at least near major hurricane strength.
Milton should be approaching the west coast of the Florida
Peninsula by early Wednesday with high wind and storm surge
threats. Additionally, tropical moisture will stream into Florida
even ahead of Milton for heavy rain Tuesday, and then certainly
along Milton`s track across the peninsula on Wednesday. Elsewhere,
an upper trough (anchored by an upper low that may track over or
near New England) will settle over the East for a few days next
week as an upper ridge upstream tracks from the West to Central
U.S. bringing a period of climatologically warm weather. By later
next week, the leading edge of a Pacific trough will produce
gradual height falls over the Northwest with some generally light
precipitation to accompany.


...Guidance/Predictability Assessment...

Now that Milton has formed, model guidance is indicating it to
strengthen to hurricane strength with some signal for a major
hurricane as it tracks east across the Gulf. There are notable
model differences in the timing and track of Milton though. The CMC
remains a very slow outlier that was not preferred. The EC-based
AIFS has been one of the fastest pieces of guidance, but has slowed
down somewhat closer to operational guidance. Other AI models from
the 00Z cycle were split, some faster like the AIFS and some
slower like the operational EC, but will be interesting to see how
the 12Z AI models handle Milton now that it has formed. In general
the operational models are faster with showing landfall of Milton
early Wednesday compared to a day ago. The 12Z ECMWF has slowed a
bit from its 00Z run as it crosses Florida, which increases
rainfall amounts. In any case, the NHC track seems to be a
reasonable middle ground favoring the GFS/ECMWF. Milton may have a
slow transition from tropical to extratropical as it is very close
to frontal boundaries, and cyclone phase space diagrams generally
show a lengthy period of an asymmetric warm core storm.

Farther north with the main jet stream, models are reasonably
agreeable with the pattern described above. The Pacific trough
shows the most spread, as the ECMWF is on the slower side in
bringing troughing into the West than other guidance, including
some AI models. A middle ground/blended solution with its timing
seemed best.

The WPC forecast utilized a blend of the 00/06Z deterministic
GFS/ECMWF/UKMET runs early in the period, with increasing
proportions of the GEFS and EC ensemble means later next week.


...Weather/Hazards Highlights...

Milton is forecast to be a hurricane, possibly near major
hurricane strength, as it tracks across the eastern part of the
Gulf Tuesday and approaches Florida. There is an increasing risk of
life-threatening storm surge and wind impacts for portions of the
west coast of the Florida Peninsula beginning late Tuesday or
Wednesday. Residents in these areas should ensure they have their
hurricane plan in place, follow any advice given by local
officials, and check back for updates to the forecast.
Additionally, enhanced tropical moisture will be in place across
Florida with wavy fronts on Tuesday even before Milton approaches,
promoting heavy rainfall, with more to come on Wednesday as Milton
is forecast to cross the state. Upgrades to Slight Risks are
planned in the ERO for Days 4-5/Tuesday-Wednesday for portions of
Florida.

Elsewhere, the upper low over/near New England should allow for
some lake-enhanced rain within in westerly flow across the Great
Lakes. A mean frontal zone with one or more embedded waves should
reach near the northern Pacific Northwest by early-mid week,
producing some periods of light to locally moderate rain and non-
zero chances of snow in the highest elevations. Widely scattered
showers are possible at times across the Four Corners states into
parts of the south-central U.S., but anything beyond light rain is
unlikely.

The strong and persistent western-central U.S. upper ridge will
promote an extended period of well above normal temperatures over
that part of the country. Gradual eastward drift of the ridge axis
will shift the highest anomalies from the West into the Plains by
Tuesday, and some northern locations could reach 20-30F above
normal persisting into mid- and late week. Meanwhile height falls
slowly pushing in over the West Coast will support a trend toward
near normal temperatures by Wednesday or Thursday. Temperatures
over most of the East should be cooler as upper troughing sets up
near the East Coast. This may lead to frost/freeze concerns across
portions of the Upper Great Lakes region and interior Northeast,
with the timing around the median to a bit late for the first
frost/freeze of the season.


Tate/Santorelli


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







$$