Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EDT Thu Aug 29 2019
Valid 12Z Sun Sep 1 2019 - 12Z Thu Sep 5 2019
...Hurricane Dorian forecast to affect Florida and parts of the
Southeast U.S. by this weekend/early next week...
...Expected Weather Pattern...
An upper level ridge centered over the Four Corners region on
Sunday and a broad trough over the north-central U.S. is expected
to prevail going into the early part of the week. An upper low
off the Pacific Northwest coast will likely move inland and spur
the development of a surface low and cold front across southern
Canada and the northern Plains by the end of the forecast period.
Hurricane Dorian will be steered by a building upper level ridge
over the western Atlantic and likely result in a turn towards the
west-northwest towards Florida by early next week.
...Model Evaluation...
Beyond Sunday night, model spread increases substantially in the
eventual evolution of the closed low/trough near the Pacific
Northwest, with the GFS faster to bring an embedded shortwave
impulse inland compared to the ECMWF and CMC, and the UKMET
remains stronger with the upper level ridge over the Intermountain
West. Confidence is below average by Tuesday and beyond owing to
big timing and amplitude differences noted across southern Canada,
and a mainly ensemble blend was incorporated into the forecast by
that time. In regards to Dorian, the GFS remains to the north of
the model consensus, and the latest 00Z CMC, ECMWF, and UKMET
appear to be close to each other on Monday as the storm approaches
Florida.
...Sensible Weather...
The main weather story will be Hurricane Dorian and its eventual
track towards the Southeast U.S. late Sunday and into Monday, with
the Florida Peninsula likely to be directly affected. Heavy rain
is expected across much of central Florida and eventually towards
the Florida Panhandle by Tuesday as the storm is expected to track
in that general direction, although less certain by that time.
Forecast rainfall amounts have increased some since the previous
forecast and more concentrated near the expected track, and
damaging winds can also be expected along with storm surge near
the coast. The National Hurricane Center has additional
information pertaining to the hurricane and its forecast over the
next several days.
Elsewhere across the continental U.S., a relatively dry weather
pattern is likely across much of the central and western U.S. next
week owing to the large upper ridge in place and the lack of any
major storm systems. There will likely be some episodes of
showers and storms from the Dakotas to New England with shortwave
impulses tracking eastward around the ridge, but no significant
heavy rainfall events appear likely away from the southeastern
U.S. Temperatures are forecast to be about 5 to 15 degrees above
average across the western U.S. early in the forecast period
before returning closer to normal values by the end of next week.
Slightly below normal temperatures return to the northern Plains
by midweek after the passage of the cold front.
Hamrick
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at:
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/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml