Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
222 PM EDT Monday Aug 31 2015
..Flood Watch in effect through this evening...
Short term (tonight - tuesday)...
models remain in reasonably good agreement with synoptic scale
features during the short term period so a blend will be used. A
trough of low pressure (the remnants of erika) over the eastern
Gulf this afternoon will continue to move slowly to the west-
northwest toward the northern Gulf Coast tonight through Tuesday.
In the wake of the trough high pressure surface and aloft will
build in over west central Florida from the Atlantic with a more
typical Summer time pattern returning to the forecast area for the
remainder of the week.
As for the rest of this afternoon abundant tropical moisture (pw's 2+
inches) combined with the trough...daytime heating...upper level
support...lingering upper level divergence and the sea breeze
boundaries will all support numerous shower and thunderstorm
development across the forecast area...with the potential for some
locally heavy rain where the training of storms occur.
Tonight the showers and storms should gradually wind down after
sunset across central and southern interior sections where mainly
dry conditions should prevail after midnight as slightly drier middle
level air works its way in from the southeast. The exception to
this will be along the immediate coast from Sarasota County north
to Pinellas County and across the Nature Coast counties where
shower and storm chances will likely continue overnight along the
ribbon of deeper moisture in the vicinity of the trough axis.
On Tuesday the lingering trough and deepest moisture axis (pw's in
the 2.2 to 2.4 inch range) across the Florida Big Bend region and
Northern Peninsula will keep rain highest in these locations (pops
around 70 percent) while central and southern zones should return
to a more typical Summer-time regime with scattered (pops 50
percent) diurnal storms developing along the sea breeze by late
morning with the convection then moving to inland locations during
the afternoon. Overall moisture levels will remain
high...especially across northern zones...so the threat for some
locally heavy rain will be possible in some locations. However
with the deepest moisture and lift associated with the trough
shifting northward the overall threat for widespread heavy rain
should diminish tonight into Tuesday so at this point in time do
not plan to extend the Flood Watch and will let it expire at 00 UTC
(8pm edt) tonight.
Temperatures will run close to normal with lows tonight ranging
from the lower to middle 70s inland areas...and upper 70s along the
coast with highs on Tuesday climbing into the upper 80s to lower
Long term (tuesday night - monday)...
global models through middle week remain in decent agreement
regarding the forecast synoptic pattern. Both GFS and Euro are
depicting deep layer ridging setting up over Florida with a robust
upper level ridge sitting on the state through Friday. This will
help US return to a more typical summertime pattern of diurnal
thunderstorms developing on the sea breezes with the best
coverage focusing on the sea breeze convergence. Even with a
decent...but very broad...ridge in the middle to upper
levels...plenty of moisture is available through the column as
forecast soundings are showing precipitable water generally in the 1.8- 2.00"
range. Combined with plenty of low/middle level instability and
lifting along the sea breeze expect to see scattered to numerous
thunderstorms develop each afternoon along the sea
breeze...generally favoring inland areas east of the I 75
corridor. Temperatures for the period will generally run a couple
degrees above early September normals.
brief periods of MVFR/IFR conditions will be possible at the
terminal sites through 02z tonight as developing rain showers/thunderstorms and rain move
across the region. Outside of the convection VFR will prevail.
Tonight through middle morning on Tuesday mainly VFR is expected but
additional brief MVFR/IFR will be possible after 16z as more
rain showers/thunderstorms and rain develop over the region. South to southwest winds in the
8 to 10 knot range with gusts up to 30 knots in the vicinity of
thunderstorms and rain this afternoon will become southeast and diminish to 5 knots
or less after 03z tonight.
a surface trough (remnants of erika) over the eastern Gulf this
afternoon will move west northwest toward the northern Gulf
region through Tuesday where it will wash out through Wednesday.
In the wake of the trough high pressure surface and aloft will
build in over the waters with light southeast to south winds and
slight seas expected the remainder of the week...with an onshore
sea breeze component developing along the coast each afternoon.
Winds and seas may be higher in the vicinity of thunderstorms
each day...otherwise no headlines are expected.
abundant moisture and elevated rain chances will keep humidity
values well above critical levels through the remainder of the
week with no fire weather issues expected.
heavy rainfall over the region dating back to late July has
brought numerous rivers across the area into minor or moderate
flood. Additional rainfall is forecast for the first half of the
week as the remnants of Erika skirts the Florida Peninsula...which
will exacerbate existing river flooding. Earlier thoughts on the
heavy rain have been tweaked lower but 7 river points still remain
in flood or forecast to reach flood stage this week. Visit
weather.Gov/Tampa and click 'rivers/lakes' along the right hand
side for up to date forecasts on each river forecast point.
Residents living along rivers or faster flowing streams should
monitor water levels and be ready to move to higher ground should
flooding be observed.
Preliminary point temps/pops...
tpa 76 90 78 91 / 50 50 60 60
fmy 76 92 77 92 / 30 50 50 60
gif 75 92 76 93 / 40 50 60 70
srq 76 89 77 90 / 50 40 40 30
bkv 74 90 74 92 / 50 60 60 70
spg 77 89 79 91 / 50 50 50 40
Florida...Flood Watch until 8 PM EDT this evening for coastal
Charlotte-coastal Hernando-coastal Hillsborough-
coastal Lee-coastal Manatee-coastal Pasco-coastal
inland Hernando-inland Hillsborough-inland Lee-inland
Manatee-inland Pasco-inland Sarasota-Pinellas-Polk.
Short term/aviation/marine/fire weather...57/McMichael
long term/decision support...20/Barron