Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
400 PM EDT Thursday Aug 21 2014
..hot days of Summer across west central and southwest Florida...
Short term (rest of today-friday)...
hot day continues across west central and southwest Florida. Some
showers and thunderstorms have developed across the interior and
southwest Florida this afternoon. With the high pressure over the
Gulf shifting west...these storms will tend to have a northeast
flow. Expecting coverage to increase as convection is able to tap
available instability from today/S heat. Heat index values remain
below the 108 degree heat advisory criteria across the area and
are expected to remain that way on Friday.
On the temperature side of the forecast...hot continues to be the
trend. Preferred a blend of the 12z GFS mav/12z NAM met/00z European model (ecmwf)
MOS guidance with heavy weight also given to the GFS ensemble
mean. The spread between guidance was minimal...granting higher
confidence than the last few days. One of the biggest factors in
the forecast will be cloud and shower/thunderstorm
development...time and locations will affect temperatures. A sea
breeze is expected again on Friday...providing an additional
trigger along with slightly increased moisture.
Long term (friday night-wednesday)...
the extended portion of the forecast features two systems having
the potential to influence our weather. The first is the tropical
disturbance approaching the Lesser Antilles. The 00z suite of
guidance is in pretty good agreement in taking the disturbance
west-northwestward toward Hispaniola during Saturday...then
turning more northward toward the eastern Bahamas after that. By
no means is this a guarantee but the forecast will follow this
scenario for now.
The second feature is a weak back-door cold front forecast to move
southward into North Florida by Sunday...then into central or
South Florida by Monday. Saturday may be our last drier than
normal day before the front moves in by Sunday. The European model (ecmwf) does
bring drier air in behind the boundary which would keep our rain
chances below normal. The European model (ecmwf) also has a rather weak reflection
of the tropical disturbance moving northward well east of the
Carolinas on Tuesday while the other global models including the
Canadian and GFS have a more robust system near or east of the
Bahamas. A tropical cyclone moving northward near the Bahamas
would typically put is in the dry/subsident region of the system.
With so much uncertainty...did not want to put too much stock in
any one of the global models so stayed pretty close to climatology
with highest rain chances over our northern zones on Sunday with
the advancing cold front then over our southern zones Monday
through Thursday more typical of climatology.
We will also finally get into more of an easterly flow regime
which will bring more afternoon storms toward the Gulf Coast
rather than moving quickly inland as we have seen for much of
VFR through the period...with MVFR/IFR briefly possible if
convection moves across a terminal in the afternoons. Sea breeze
pushing inland...will retreat later tonight restoring light winds
overnight. Repeat of this pattern for Friday.
high pressure centered over the central Gulf of Mexico will keep
winds out of north northwest direction below 15 knots and seas
less than 2 feet through the week and into the weekend. Thunderstorm
chances will also remain minimal for the next couple of days with
little more than isolated showers and a few thunderstorms. Showers
and storms will increase on Sunday and into the beginning of next
week as a weak cold front moves over northern Florida.
no fire weather concerns through the weekend.
Preliminary point temps/pops...
tpa 79 93 80 94 / 20 30 10 20
fmy 77 93 78 94 / 20 30 10 20
gif 77 96 77 96 / 20 30 10 30
srq 78 91 78 92 / 20 30 10 20
bkv 73 94 74 95 / 20 30 10 20
spg 81 93 81 93 / 20 30 10 10
Short term/aviation/fire weather...02/Garcia and 99/bhagwandin
middle term/long term...63/jillson
decision support services...57/McMichael