Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
301 PM EST sun Feb 1 2015
Short term (today - monday)...
high pressure exits eastward as the next frontal system moves
across the central United States this afternoon. Southeast to
south winds are carrying moist air over the peninsula of
Florida...creating the potential for patchy ground fog overnight.
Temperatures should remain a tad warmer tonight compared to
previous nights thanks to the moist airmass and increasing cloud
cover. Preferred a blend of model guidance...as spread was minimal
for the overnight.
Model guidance begins to diverge a tad on Monday with the GFS
offering a faster solution for the progress of the frontal
boundary compared to the slower NAM. The European model (ecmwf) is close to the
GFS...as is local high resolution model guidance. Preferred a
middle-of-the-Road blend with more weight towards the GFS timing.
Rain chances should be on the decrease as the front heads south
across the area and loses the upper level support of 500 mb
trough. Temperatures on Monday will be heavily dependent on the
cloud cover and frontal timing.
Have included some mention of thunderstorms in the forecast along
the front as there could be enough instability to support a few
storms...but not enough to go above a slight chance. The best 0-1
km helicity values in the guidance appear to be around 06-12z on
Monday...with both the GFS and European model (ecmwf) offering values around 200
m2/s2. Do not believe any convection will be around to tap into
this shear...due to the lack of instability. Storm Prediction
Center discusses in their day 2 outlook /swody2/ that the severe
risk should be minimal with this front.
Long term (monday night - sunday)...
a progressive amplified split-flow pattern will persist across the
Continental U.S. During the long term period. Models remain in relatively good
agreement with synoptic scale features so a blend will be used. At
the start of the period an upper level trough will be moving off the
East Coast with an attendant cold front exiting to the south of the
state. Cool air advection in the wake of the cold front will usher
in cooler drier air on a breezy northwest to northerly wind flow
which will last through early Tuesday.
During Tuesday night into Wednesday pleasant dry weather is
expected as zonal flow aloft develops and surface high pressure
moves off the middle Atlantic coast with an return easterly flow
supporting milder conditions.
By late Wednesday into Thursday the surface high will shift
further east into the Atlantic as a closed low that has been
anchored over southern Baja California/Mexico region opens up and ejects
eastward across the northern Gulf. As this system moves east it
will dampen out as it encounters a confluent flow aloft...but will
still help to induce low pressure development over the western
Gulf Wednesday night. Models continue to differ some with the speed
placement and intensity of this low as the overall evolution of
this system will depend on how much interaction it has with the
northern stream flow...thus confidence in any model solution is
rather low at this time...but models do agree that it will track
east along the northern Gulf Coast on Thursday...moving across the
northern or north-Central Peninsula during Thursday afternoon and
then exiting east into the Atlantic Thursday night and Friday.
Ample moisture accompany this system will bring another round of
showers and possibly a few storms to the region along with the
possibility of some locally heavy rain given an increasing divergent
flow aloft beginning Wednesday night and continuing through Thursday
as it affects the region...with some additional low rain chances
continuing on Friday as another upstream short wave trough (trailing
this system) moves southeast across the region.
During Saturday and Sunday a dry northwest flow aloft and surface
high pressure building in from the north will provide pleasant dry
weather across the forecast area. After a brief cool down on Tuesday
in the wake of the first front temperatures should run close to
normal through Thursday before cooling down again Friday and into
the first half of the weekend.
VFR through much of the period...with some MVFR ceilings possibly
sneaking into the area overnight ahead of the next frontal system
on Monday. Winds should remain southerly to close the weekend and
turn west then northwest behind the front.
low pressure over the Ohio Valley and high pressure off the southeast U.S.
Coast slide eastward with a cold front sweeping through the Gulf...
Crossing the coastal waters Monday accompanied by showers...thunder-
storms...and exercise caution winds. High pressure dominates the
Gulf Tuesday through Thursday. This high slides off to the east during the
end of the week as low pressure with a trailing cold front forms in
the Gulf. There is some unable-certainty with timing and location but
thunderstorms and robust to strong winds may be possible.
no fire weather concerns expected with several fronts expected to
creating wetting rains and keep relative humidity values above
concern thresholds. Overnight fog tonight should be patchy in
nature and not create much of a concern.
Preliminary point temps/pops...
tpa 61 69 45 66 / 10 60 0 0
fmy 61 76 53 72 / 10 40 10 0
gif 59 74 46 67 / 10 70 0 0
srq 61 71 49 67 / 10 60 0 0
bkv 57 70 38 65 / 10 70 0 0
spg 62 69 50 64 / 10 60 0 0
Short term/aviation/fire weather...02/Garcia
long term/decision support...57/McMichael