Scientific Forecaster Discussion
fxus62 ktbw 281852
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
252 PM EDT sun may 28 2017
18z water vapor and h4 rap analysis shows an amplified
upper level pattern in place across the Continental U.S....with ridging
on both the Pacific and Atlantic coasts...and deep
troughing through the mid-section of the country. However,
the trough energy rotating through the middle of the country
will have little to no impact on our local weather, as a
large area of mid/upper level ridging covering the Florida
Peninsula/Gulf of Mexico acts as a protective shield from
any inclement weather through the early portion of the week.
The subsidence inversion associated with this ridge was
very evident on the 12z ktbw sounding between 900-940mb,
with expected significant drying above this level.
At the surface, subtropical ridge axis over the western
Atlantic ridges westward over the southern half of the
Florida Peninsula and eastern Gulf of Mexico. This is a
fairly typical Summer-like pattern for our area, and the
current position provides generally light westerly to
variable large scale flow. Local winds rest of today through
Monday will be more dominated by the development of the
diurnal sea- breeze and land-breeze during the day and night
respectively. This influence will be greatest to the south
of the I-4 corridor...in closer proximity to the ridge axis.
Short term (rest of today through monday)...
rest of today...a warm and benign weather pattern in place.
Diurnal temperature rise under the stacked upper ridging
has been efficient, reaching the lower to middle 90s inland
and into the 80s at the beaches. The atmospheric column
remains much to dry and thermodynamically hostile to allow
any deep convection along the sea-breeze this
afternoon. Visible satellite imagery shows only a shallow
and suppressed cumulus field underneath the suppression of
the ridge...and so rain chances will remain near 0%.
Tonight...dry and seasonable. Sea-breeze will slowly
dissipate into the later evening hours. Winds will be light
westerly north of the I-4 corridor...and shift light east or
northeasterly (offshore) further to the south. Similar to
this morning, the presence of strong stacked ridging aloft
overtop shallow boundary layer moisture is favorable for the
development of shallow field fog to develop after midnight.
Normally more fog prone areas will have a good potential to
see this field fog develop, however, the shallow nature of
the fog means it will very quickly burn off after sunrise
Monday morning. Low temperatures in the mid/upper 60s inland
and lower to middle 70s at the coast.
Monday...the broken record continues. Stacked ridging for at
least on more day. There will be a subtle increase in column
moisture, however, all indications are that conditions will
remain hostile enough toward deep convection to prevent
anything but very isolated late afternoon showers. If they
will occur (and this is a big if)...it would be down toward
Fort Myers. However, for now going to keep only 10% pops in
the forecast for these southern zones, as much higher
potential for any one location to stay dry. Temperatures
climbing well into the 90s away from the coast Monday
afternoon. Normal hotter locations of far inland
Polk/Highlands/DeSoto/Hardee counties have some potential to
top out in the upper 90s. Even near the coast temperatures
may flirt with 90 before the sea-breeze develops and drops
temps back into the middle 80s.
Everyone have a safe and fun Holiday weekend. Remember that
sunscreen for outdoor activities as the sun is nearing peak
strength this time of year.
Long term (monday night - sunday)...
Monday night and Tuesday, mid level high pressure over the
western Atlantic will be ridging into the Florida Peninsula
but will gradually shift east of the area through mid week
as a broad trough sets up over the northeastern Continental U.S.. at
the surface, the subtropical ridge centered over the
Atlantic will hold across the Florida Peninsula through the
week, with relatively light low level flow and daily sea
breeze circulations. A few afternoon showers or
thunderstorms will be possible over the interior on Tuesday,
but relatively dry air and subsidence will prevent
widespread rain chances.
Through the second half of the week, with the upper level ridge
moving away, atmospheric column moisture will gradually increase,
leading to building thunderstorm chances. The best chances will
generally be over the interior, although south of Tampa Bay weak
easterly/southeasterly flow will allow the sea breeze collision and
highest storm coverage to occur closer to the coast.
Temperatures will be a few degrees above normal Tuesday and through
Thursday with highs over the interior in the mid 90s and around 90
along the coast. As subsidence aloft decreases and low level
humidity increases, temperatures will moderate to around normal
Friday through the weekend.
Aviation (28/18z through 29/18z)...
general VFR conditions across west-central and southwest
Florida through the day. Onshore sea-breeze winds diminish
to light westerly after sunset. Another round of shallow
patchy field fog possible after 08z tonight...mainly once
again for klal and kpgd. Sea-breeze winds again develop
onshore during the early afternoon hours of Monday.
Atlantic high pressure continues to ridge westward across
the southern half of the Florida Peninsula into the eastern
Gulf of Mexico through the early portion of the week. The
close proximity of the ridge axis and position will provide
a generally light westerly to variable large scale flow
across the region. Winds will become a bit more gusty and
onshore near the coast each afternoon/early evening with
the development of the daily sea breeze.
high pressure remains in control of the region through the early
portion of the week. No rain is expected through Monday, with only
a slight chance of a few showers late Tuesday afternoon. Conditions
across the interior are expected to be quite dry Monday afternoon
with widespread sub-critical levels of relative humidity. The only
counties that currently are expected to be close to red flag
conditions based on relative humidity and erc would be Highlands
and Polk. Red flag warnings may become necessary for these counties
if current forecasts hold. A slow influx of low level moisture will
likely prevent any red flag conditions by Tuesday afternoon.
Fog potential...normally fog prone areas away from the immediate
coast will have the potential for some shallow field fog late tonight
and again late Monday night. The fog will be very shallow and burn off
within an hour or two after sunrise.
Preliminary point temps/pops...
tpa 75 91 75 91 / 0 0 0 20
fmy 73 93 75 92 / 0 10 10 20
gif 72 98 73 96 / 0 0 10 30
srq 74 86 74 86 / 0 0 0 20
bkv 71 92 71 93 / 0 0 0 20
spg 76 91 75 91 / 0 0 0 10