Scientific Forecaster Discussion
fxus62 ktbw 270727
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
327 am EDT Tue Jun 27 2017
07z water vapor and h4 rap analysis continues to be characterized by
a longwave pattern of upper ridging over the inter-mountain west and
downstream to the east of the Continental Divide. The Florida
Peninsula resides within a zone of weaker flow aloft...lying just
south of the eastern Continental U.S. Trough, and generally north of the
influence from upper ridging extending from the southeast Gulf of Mexico to
the Bahamas. This region with which we sit is characterized by a
decent amount of column moisture (pw ~ 2") and no apparent hostile
levels aloft from a thermodynamic Point of View. The 00z ktbw
sounding no longer showed any significant subsidence/inversions...as
the ridge has settled far enough south.
At the surface...quasi-stationary boundary remain in place over the
northern portion of the peninsula early this morning. This boundary
became the focus for some rather heavy rainfall and strong storms
during Monday afternoon/evening, and may very well repeat this
situation today. The gradient over the region is very weak today
between this boundary and the subtropical ridge axis...located over
the far southern peninsula. Expecting the the region will see a good
deal of solar insolation this morning...and force a well defined sea-
breeze after midday...with decent inland prorogation by the end of
Short term (today through wednesday)...
today...scattered storms will start the day over the coastal waters
along residual outflow/land breeze boundaries...with the flow
allowing a few of these to migrate back toward the coast of
Levy/Citrus counties early in the am. Otherwise, the morning hours
will generally be dry over the landmass, with plenty of solar
insolation supplying the terrestrial heating to force a sea-breeze by
midday. The gradient is very weak across the region, but if anything
is light SW. This synoptic flow will help move the sea-breeze
inland through the afternoon hours. Therefore, initial scattered
convection along the coastal plain from midday through early
afternoon, will become more numerous late afternoon and especially
this evening over the interior, and leaving areas closer to the
coast...generally dry late in the day. Better chances for additional
convection will occur near the coast for our northern Nature Coast
zones where the synoptic frontal boundary will supply the focus for
one more day, but elsewhere along the I-75 corridor from Tampa Bay
southward, the late afternoon/evening have a good potential to be
mostly dry. Inland areas from the villages, to eastern
Polk/Highlands counties may be a very different story with a stormy
evening forecast...possibly as late as midnight over Polk/Highlands.
Tonight...lingering storms over the interior slowly diminish through
06z...followed by a dry rest of the overnight for the land zones.
Will see a well defined land-breeze develop tonight, forced partial
by the diurnal cooling, but also a slowly developing east/east-southeast synoptic
flow in the lower levels as high pressure builds to our north. Will
likely see another early morning with widely sct storms over the
Wednesday...the 1000-700mb low level flow becomes light but fully
east-southeast during Wednesday. The flow will be light enough to allow a sea-
breeze to develop and move onshore, but prevent the type of inland
propagation we are expecting to see today. This pattern should lead
to the most active convection staying a bit closer to the coast
later Wednesday afternoon/evening. The pattern would suggest the
storms consolidate along the I-75 corridor itself, but would not be
surprised to see the outflow strong enough to build storms all the
way back to the coast through the evening hours.
Long term (wednesday night - tuesday)...
troughing extends from near Nova Scotia southward along the New
England coastline. A little closer to home, a typical Summer time
pattern will continue over the region. Upper level ridging extends
over the Bahamas westward through the Florida Peninsula and into the
Gulf of Mexico. This pattern will hold through the period with very
little variation through the week. On the surface, subtropical high
pressure near Bermuda ridges west-southwest over southern Florida. A
weak frontal boundary over northern Florida washes out and
dissipates as high pressure moves off the mid-Atlantic coast by
Wednesday evening. This will keep a general east-northeast through
southeast wind flow over the region through the week. Rain chances
will be typical for the Summer time with 50-70 pops each day through
the week, with the highest coverage over the interior counties.
Temperatures will remain near seasonal averages with upper 80's
to low 90's during the day and overnight lows in the mid 70's.
Aviation (27/08z through 28/06z)...
prevailing VFR for all terminals through the morning hours.
Sea-breeze will turn winds onshore after midday and push
inland through the terminals during the afternoon hours.
Expect storms to form along this boundary and push inland as
well. A brief MVFR/IFR restriction is possible with any
passing storms, but otherwise VFR will continue through the
taf period. The majority of storms look to move inland from
the terminals by the evening hours. Klal would likely be the
last to see the storms end.
a weak pressure gradient remains over the eastern Gulf of Mexico
through the end of the week...keeping winds and seas generally
light, outside of scattered thunderstorms.
no significant fire weather concerns are expected through the next
several days as relative humidity values remain well above critical
levels, the potential for wetting rainfall remains high, and winds
remain generally low, outside of thunderstorms.
Fog potential...no significant area of fog or visibility reduction
are anticipated through the next several days.
Preliminary point temps/pops...
tpa 90 76 92 76 / 50 10 50 20
fmy 91 75 93 74 / 50 20 60 30
gif 91 73 92 75 / 60 40 60 20
srq 86 76 87 76 / 50 10 40 20
bkv 90 73 91 74 / 40 10 60 20
spg 89 77 91 78 / 50 10 40 20