Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Tampa Bay Ruskin Florida
455 am EDT Thursday Jul 10 2014
..updated to include middle term and long term discussions...
Short term (today and tonight)...an upper-level trough over the
eastern half of the country today will begin to lift out to the
northeast tonight. Most of the dynamics associated with the trough
will bypass our region to the north. There could be some enhancement
to our afternoon showers and storms over Levy County...but not
expecting any severe storms at this time.
Otherwise...typical convective pattern expected for a westerly
flow regime. Scattered morning showers and storms near the coast
will become more numerous as they move inland during the
afternoon. Highest coverage is expected to be south of the Tampa
Bay area where prevailing westerly winds will be much lighter due
to the location of the ridge axis.
There could be a few lingering storms this evening but expect most
of the activity to be gone by around midnight. Scattered showers
and storms should develop along a land breeze boundary over the
Gulf late at night and move toward the coast around sunrise.
Middle term (friday and saturday)...
global guidance remains in good agreement regarding the synoptic
pattern over the forecast area for the end of the week. Upper level
ridge will briefly break down on Friday as a subtle weakness on the
far southern periphery of an eastern Continental U.S. Trough pivots across the
northern half of the state. This weakness will shift east into the
Atlantic during Saturday allowing upper level ridging to become
re-established overhead for the second half of the weekend.
At the surface...subtropical ridge axis will remain over the central
Florida Peninsula through the middle term period. The position of the
ridge axis will result in a variable 1000-700mb wind flow along and
north of the I-4 corridor...and a weak easterly flow further south.
Either way the flow will be weak and thunderstorm coverage looks to
be generally uniform...with perhaps slightly higher probability of precipitation along the
Suncoast where the light easterly flow will favor sea-breeze
convergence. Have been watching the models struggle with the
strength of a swath of drier air arriving aloft from the east/southeast
during Friday/Friday night. Current thinking is that although the
middle-levels will dry out somewhat...the overall impact does not look
to be enough to have a significantly negative effect on the process
of deep convection. Any drier air looks to fade quickly during
Saturday and expect any impacts from this feature to be gone by the
second half of the weekend.
What does it all mean for your forecast. Well...with no significant
ridge or trough in place...temperatures should be right near climatology.
Thunderstorms will be around mainly each afternoon and
evening...although do not be surprised to see a few showers near the
coast during the morning hours of Friday...especially from Pinellas
County northward along the Nature Coast.
Long term (sunday through next wednesday)...
during the second half of the upcoming weekend and early portion of
next week...the eastern Continental U.S. Trough will quickly exit and deamplify
into the western Atlantic allowing upper ridging to once again build
over the northern Gulf and Florida Peninsula. The evolution of the
subtropical ridge axis has not changed in the global guidance and
still is expected to sink southward to an axis position over the
southern portion of the peninsula by early next week. The flow
pattern is rather variable for Sunday...which in terms of
climatology translates to a more uniform 40-50% pop for the area.
As the ridge axis drops south...1000-700mb mean flow will come
around to a more SW direction...which tends to result in more
coastal morning showers...and then higher rain chances inland for
the afternoon/evening as the sea-breeze is pushed away from the
coast by the prevailing synoptic flow. Have not made any significant
changes to the previous forecast as this pattern has been fairly
stable in the global guidance for the past several runs. Either
way...we are looking at generally typical Summer conditions...with
no significant synoptic influences to deviate from day to day
climatology. The "dog days" of Summer are here.
same general weather pattern with scattered storms near the
coastal tafs in the morning pushing inland during the afternoon.
Best chance at seeing brief IFR/LIFR will be at lal and rs/fmy.
Timing uncertain so handling with vats at this time.
surface ridge axis over central Florida today will lift to North
Florida by the weekend...then back south on Monday. The pressure
gradient on either side of the ridge is weak so expect winds to
remain at or below 10 knots and seas 2 feet or less outside of
thunderstorms through Monday.
no humidity concerns. Today will be another day of light winds and
poor to fair smoke dispersions.
Preliminary point temps/pops...
tpa 90 77 92 77 / 40 30 60 30
fmy 92 74 92 76 / 60 40 50 30
gif 92 74 92 75 / 60 30 60 20
srq 90 75 90 77 / 30 30 40 30
bkv 92 71 93 73 / 50 20 60 30
spg 90 78 91 79 / 30 20 50 30
Short term/aviation/marine/fire weather...jillson
middle term/long term...mroczka