Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
407 am EDT Wednesday Jul 23 2014
..another Summer day across west central and southwest Florida...
Short term (today - tonight)...
weak surface flow from Atlantic high pressure continues over the
peninsula of Florida this morning. Aloft...a 500 mb low continues
to linger over the northern Gulf of Mexico. Showers are developing
along a boundary offshore...this activity could potentially move
ashore this morning as the sea breeze develops. Some patchy ground
fog has developed over inland portions of west central and
southwest Florida this morning...expect it to dissipate shortly
Today will be another sea breeze thunderstorm day for much of west
central and southwest Florida...with the lowest rain chances along
the Nature Coast. 500 mb temperatures around -6 degree c mitigate
large hail concerns with strong thunderstorms...though the slow-
moving nature of these storms will once again present lightning
and heavy rain concerns. Slow-moving thunderstorms that develop
quickly overhead present a danger to those outdoors. If the skies
become dark quickly or thunder roars...seek safe shelter indoors
or in an enclosed metal vehicle. Temperatures in the 90s in most
places could push heat index values near 100 today. 00z GFS mav
guidance was a bit warmer than the 00z NAM met guidance...likely
due to the NAM/met featuring higher cloud cover and rain chances.
As the afternoon thunderstorms lose the heating of the day in the
evening...the inland activity will begin to diminish gradually.
The retreating sea breeze could bring shower and storm activity
back close to the coast before moving offshore. Overnight...offshore
activity is expected again along the remnant boundaries.
Temperatures will be in the 70s...with little spread between
Middle term (thursday - friday)...
models remain in good agreement with synoptic scale features
during the middle term period so a blend will be used. A closed middle
level low offshore the la/Texas coasts at the start of the period
will weaken and become absorbed into the amplifying upper level
trough over the eastern U.S through Friday. The amplifying upper
trough will help to keep the upper and surface ridge suppressed
across the south-Central Peninsula through the period which in turn
will support a southwest wind flow across the forecast area. Ample
moisture within this flow will favor isolated showers and storms
along coastal locations during the late night and early morning
hours...then shifting east and becoming scattered to numerous in
coverage along the sea breeze over inland locations each afternoon.
Similar to previous days a weak steering flow will result in slow
moving storms with some locally heavy rainfall amounts possible each
day. The onshore flow will support above normal low temperatures
along the coast where readings in the upper 70s to around 80 can be
expected...with middle 70s over inland areas with daytime highs in the
lower to middle 90s.
Long term (friday night - tuesday)...
models shows an amplifying upper level pattern developing over
the Continental U.S. During the long term period with a strong upper ridge
noted out west and a deepening upper trough over the east. The
deepening upper trough across the eastern U.S. Will keep upper
and surface ridging suppressed across the south-Central Peninsula
through the period with a deep layered southwest wind flow
continuing across the forecast area. Ample moisture combined with
sea breeze and outflow boundary interactions will support diurnal
convection across the forecast area each day...with the southwest
flow favoring isolated showers/storms along the coast during the
late night and early morning hours then shifting east and becoming
scattered to numerous over inland locations each afternoon. Models
this morning are showing some drier middle level air moving into the
region during Monday and Tuesday ahead of a cold front which will
be sinking south toward the northern Gulf Coast in association
with the aforementioned upper trough. If these trends continue
then rain chances may need to be lowered some in later forecasts
for these days...but for now seeing that it is summertime will
leave scattered range probability of precipitation in place for all areas and wait to see
what later model runs show over the coming days.
The onshore flow will keep nighttime low temperatures above normal
along coastal locations with readings in the upper 70s to around 80
with middle 70s over inland areas...while daytime highs will continue
in the lower to middle 90s.
morning MVFR/brief IFR ground fog and low ceilings will improve to VFR
for much of the period. Mainly light flow with a sea breeze
expected to develop later this morning and move inland by the
afternoon. MVFR/brief IFR are possible with morning showers and
afternoon/evening thunderstorms...along with gusty variability in
the winds. Convection will diminish after sunset.
high pressure continues to dominate area weather...providing light
winds and waves. Sea breeze thunderstorms are expected the next
few days...with some possible activity in the waters in the
mornings and overnights.
no fire weather concerns other than overnight/morning patchy
ground fog at low-lying fog-prone locations.
Preliminary point temps/pops...
tpa 91 78 91 78 / 40 10 40 20
fmy 92 76 91 77 / 50 20 40 20
gif 94 75 93 75 / 60 20 50 20
srq 90 77 91 77 / 40 20 30 20
bkv 92 72 92 72 / 40 10 40 20
spg 90 80 90 80 / 30 10 30 20
Short term/aviation/marine/fire weather...02/Garcia
middle term/long term/decision support...57/McMichael