Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
315 am EDT Sat may 23 2015
Short term (today - sunday)...
middle and upper level ridging will build in over the region today
through Sunday in response to a deep upper trough/closed low over
the Great Basin and central rockies. At the surface high pressure
over the northern middle Atlantic coast early today will shift east
into the Atlantic through Sunday with an increasing deep layered
east to southeast wind flow expected across the forecast area.
Ample low level moisture (pw's in the 1.6 to 1.8 inch range) and
instability combined with daytime heating will support scattered
diurnal showers and storms across the region today and again on
Sunday with an weak sea breeze likely remaining very close to
the coast due to the increased east to southeast flow which will
favor highest rain chances along the coast during the afternoon
and early evening hours.
Temperatures will run some 3 to 5 degrees above normal with lows
in the lower to middle 70s with daytime highs climbing to around 90
along the coast...and lower to middle 90s inland.
Long term (sunday night - friday)...
at the start of the week...an amplified upper level pattern will
be in place with a strong Omega ridge over the Caribbean and
eastern Continental U.S....and an amplified trough over The Rockies. Through
midweek...the upper level pattern will make little progression
with the trough slowly working into the Great Plains and the ridge
rotating to along the U.S. East Coast. At the surface...strong
high pressure over the Atlantic will be ridging into the middle
Atlantic Sunday night...and will gradually sink south towards the
southeastern Continental U.S. Through Wednesday...resulting in steady east to
southeast low level flow across the Florida Peninsula. Although
subsidence from the strong ridging will limit some of the
convection potential...precipitable water values of up to 1.8
inches and a sea breeze collision over the western half of the
Florida Peninsula will allow for around 20-40 percent chances of
storms during the afternoon and early evening hours each day
During the second half of the week...the long range models are in
good agreement regarding an upper level cutoff low and attendant
surface wave moving northwest through the Atlantic just north of
the Caribbean. This will break down the upper level ridge...and
as the upper trough comes across the eastern Continental U.S....the cutoff
low will get swept back to the northeast and remain over the open
Atlantic. Meanwhile...the surface ridge will get displaced to the
northeast...with drier air (precipitable water values of 1.25
inches or less) filling into the area Thursday and keeping rain
chances largely less than 20 percent. As the wave moves farther
away on Friday and the upper trough crosses the Florida
Peninsula...moisture will rebound slightly with rain chances of
up to 20 percent possible...mostly over the interior.
Temperatures will be warm through midweek under the strong upper
level ridge...with highs in the low 90s and upper 80s...but will
drop a couple degrees Thursday and Friday into the upper 80s. Lows
will run from the upper 60s to middle 70s all week.
brief MVFR/IFR ceilings and visibilities will be possible after
20z as rain showers/thunderstorms and rain develop and move across the region...otherwise
VFR will prevail. East southeast winds around 5 knots early this
morning will increase to around 10 knots after 15z...briefly
becoming west to northwest at the coastal taf sites after 20z as
the sea breeze develops...with gusts up to 30 knots possible in
the vicinity of thunderstorms and rain.
surface high pressure will build in from the north today through
the Holiday weekend and into early next week. As the high builds
in an increasing east to southeast wind flow is expected across
the Gulf waters with periods of cautionary or low end small craft
conditions possible through the period...mainly during the late
night and early morning hours.
humidity values are expected to remain well above critical levels
through early next week. High mixing heights in the 5 to 6kft
range though combined with increasing easterly 20 foot winds and
transport winds will yield high dispersion indices across the
forecast area the next several days.
Preliminary point temps/pops...
tpa 92 74 91 74 / 60 10 60 20
fmy 92 73 91 73 / 60 20 50 20
gif 92 72 91 72 / 50 10 40 10
srq 92 73 90 74 / 60 20 60 20
bkv 92 71 90 70 / 40 10 60 20
spg 91 76 90 76 / 60 20 60 20
Short term/aviation/marine/fire weather...57/McMichael
long term/decision support...18/Fleming