Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
355 PM EDT Tuesday Jul 22 2014
Short term (tonight-wednesday)...
an upper low is spinning over the MS/Alabama region with an upper high
offshore of the southeast US coast...with the Florida Peninsula sitting in
between the two. At the surface...weak high pressure is ridging
across South Florida from the Atlantic with weak troughing just to the
north of the area. The surface and upper ridge will shift west
over the state through Wednesday. Winds will become light and
variable overnight...with a sea breeze dominating the flow for
Wednesday afternoon. Deep moisture will continue across the area
and allow for scattered to numerous showers and thunderstorms this
afternoon through this evening. Convection should dissipate after
midnight...then return around noon Wednesday as the sea breeze
starts to set up. Temperatures will fall into the 70s
tonight...and rise into the lower 90s for Wednesday afternoon.
Middle term (wednesday night-thursday)...
models continue in relatively good agreement with synoptic scale
features during this time frame so will again use a blend. A
closed middle level low over la at the start of the period will
weaken and open up as it retrogrades west toward the Texas coast
as upper ridging over the western Atlantic builds west over the
peninsula while the attendant surface ridge axis meanders across
the south Central Peninsula. Deep moisture (pw's at or above 2 inches)
combined with daytime heating will lead to scattered to numerous
showers and storms along the sea breeze and outflow boundaries
during the afternoon and early evening hours. A very weak steering
flow will result in slow and erratic storm motion each day which
will favor some locally heavy rainfall amounts in some locations.
Temperatures will remain a few degrees above normal with overnight
lows in the middle 70s inland areas...and upper 70s to around 80
along the coast with daytime highs in the lower to middle 90s.
Long term (thursday night - monday)...
the upper and surface ridge will sink further south across the
southern peninsula during this time frame in response to the
amplifying upper level trough over the eastern United States
impinging upon it. The GFS/European model (ecmwf) differ some with how they handle
the upper trough with the GFS showing a more amplified look while
the European model (ecmwf) shows the massive upper ridge over the four-corner
area nosing southeastward across the northern and eastern Gulf
keeping the main effects of the upper trough further to the north.
Regardless of which solution should pan out...the surface ridge axis
will remain suppressed across the south-Central Peninsula through
the period...which will favor a more pronounced southwest steering
flow across the forecast area...which in turn will favor isolated
showers and storms along the coast during the late night and early
morning hours...then shifting east and becoming scattered to
numerous in coverage over inland locations each afternoon with the
convection then lingering into the early evening hours and have
depicted this scenario in the grids. Temperatures will remain a
few degrees above normal through the period with overnight lows
in the middle 70s inland areas...and upper 70s to around 80 along
the coast...with daytime highs in the lower to middle 90s.
VFR conditions will prevail...but will have scattered
thunderstorms continuing near the terminals through 23/01z. Any
storms that move over terminals will cause tempo MVFR to IFR
conditions. Winds will become light overnight with skies clearing
out...but some isolated pockets of shallow ground fog possible
mainly at inland terminals. Chances for fog are low so have left
it out of the tafs for now.
high pressure over the Gulf of Mexico ridges across central
Florida waters through Wednesday. This ridge then settles across
the southern waters on Thursday and into the weekend. The gradient
remains relaxed with light winds and lows seas. The only hazards
will be isolated to scattered thunderstorms and the higher winds
and seas in the vicinity of these storms.
Preliminary point temps/pops...
tpa 76 91 78 92 / 20 40 30 40
fmy 75 93 77 93 / 20 50 30 40
gif 75 93 76 93 / 30 60 30 50
srq 75 91 77 92 / 20 30 30 30
bkv 71 93 72 93 / 20 40 30 40
spg 79 90 80 91 / 20 30 30 30
Short term/aviation/fire weather...24/Hubbard
middle term/long term...57/McMichael