Debate de meteorólogos científicos
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
337 am EST Wednesday Dec 11 2013
Short term (today - friday)...the weakening cold front is losing
steam as it tries to drift southward through central Florida. Dew
points have dropped several degrees at Brooksville over the past few
hours...but have stayed in the middle 60s to the south. The cool
airmass is very shallow with a moist northeast flow below 1000 feet
being over-run by a warmer somewhat drier airmass at and above 2500
feet. This is generating enough lift to produce an extensive area of
low clouds across the region. The question is whether or not the
cold advection will be strong enough to keep these clouds in or if
the sun wins out and creates enough mixing to clear them out. BUFKIT
soundings from our local models indicate enough mixing to break US
out of the clouds middle to late morning so will trend the forecast
toward partly sunny by afternoon. The soundings also show US
clouding right back up again after sunset with a classic low-
level inversion trapping moist air underneath. The clouds could
hang around for most of the morning again on Thursday.
By middle-day Thursday...the secondary push of cooler and drier air
will be moving southeast across the region. While I doubt we will
see any organized shower activity with the boundary...there will be
enough low-level moisture around for a few showers as it passes
through. Most of our region will not see any measurable rain with
this front...but whatever there is should be moving through the
Nature Coast before sunrise Thursday...then through the remainder of
our area during the morning and early afternoon hours.
With strong high pressure north of US moving out into the
Atlantic...we may actually see a fairly nice day on Friday.
Temperature forecasts are always challenging when dealing with
shallow frontal boundaries. Today should still be on the warm side
if the sun manages to break through the clouds...with highs near 80
around Tampa Bay and in the middle 80s again to the south.
My best guess right now for Thursday is that the cool makes it into
the Nature Coast capping temperatures there to the upper 60s for
Levy County but still middle 70s for Hernando and Pasco counties. The
Tampa Bay area will probably stay below 80...but certainly expect to
see some upper 70s. It will still be 80 or a bit better around Fort
Thursday night could be quite chilly for the Nature Coast with some
upper 30s not out of the question in Levy County. Even Tampa should
drop into the 50s...with Fort Myers staying near 60.
We will warm slightly on Friday as winds begin to turn more
southeasterly but still generally 70 to 75 north...upper 70s central
and 80 or so south.
Long term (saturday through next wednesday)...
the next amplification to the pattern across the eastern Continental U.S. Will
come in the way of a series of shortwaves ejecting eastward from the
central and Southern Plains during the first half of the upcoming
weekend. Initial piece of energy will reach the Tennessee Valley during
Saturday with a weak area of associated low pressure moving
northeast from the central Gulf Coast...and a trailing cold front
into the central Gulf. Similar to 24 hours ago...the GFS is still
the faster solution when compared to the European model (ecmwf). However...the GFS
operational solution at this point has good support from both its
ensemble members and also from the operational Canadian model. This
support continues into early Sunday and will lean toward the
operational GFS for the timing of the front and any pre-frontal
precipitation through Saturday night.
As it stands now...the best upper jet support/diffluence and
approaching swath of synoptic support / q-vector convergence looks
to hold to our west and northwest through the daylight hours of
Saturday. Current forecast will show a generally dry Saturday with
above normal temperatures. Any shower chances should be confined to
Levy and Citrus counties...and late in the day.
Saturday night into Sunday morning looks to be the time frame when
the synoptic support and surface focus along the front will provide
the best chances for a round of showers and storms over the central
and northern portions of the Florida Peninsula. However...just about this
time...the overall energy of this system will be translating
northward into re-developing cyclogenesis along the middle-Atlantic
baroclinic zone. We see this scenario quite often in the cool season
months and it quickly weakens the dynamics/kinematics overhead along
with a stretching and weakening of the low level focus. With all
this in mind...decent rain chances initially over the Nature Coast
seem destine to decrease with southern transport of the frontal
boundary into the daylight hours of Sunday.
This "hanging up" of the frontal boundary over the state on Sunday
may keep some shower chances and more abundant clouds in the
forecast...but it does not appear to be an overall wet day and
certainly not a "washout" of a forecast.
Global guidance members in typical fashion for this time of year do
not completely agree on the synoptic pattern / wave phase by the
early and middle portion of next week...but do generally show a
pattern with the main northern stream storm track holding well to
our north. With no significant weather anomalies currently shown for
our region...will go with a generally dry forecast and seasonable
temperatures to round out the long term forecast period.
varying conditions across the region early this morning with a weak
cold front lying between Tampa Bay and Fort Myers. Areas of shallow
ground fog will continue to be an issue for some of the southern
terminals until the fronts passage helps mix the lower levels. North
of the front...periods of MVFR ceilings will be possible through 14-15z
followed by general VFR conditions for the majority of the Wednesday
daylight hours. Statistical guidance and ensemble probability
guidance are suggesting more widespread IFR/MVFR ceiling restrictions
Wednesday evening after sunset into early Thursday for the I-4
corridor terminals and ceiling and/or fog issues for kpgd south to krsw.
Will begin mention of MVFR ceilings after sunset for northern terminals
and leave restrictions out until next taf package for SW Florida
Marine...we are still seeing winds of 20 to 25 knots at buoy 42036
with seas of 7 feet. Winds along the coast are closer to 15 knots.
The current Small Craft Advisory for the offshore waters north of
Englewood still looks good. All the models show the winds relaxing
this morning and we should see winds below 20 knots with seas below
7 feet by middle morning. The next frontal boundary on Thursday will be
followed by a strong ridge of high pressure to our north. This will
again bring some 20 knot winds and 6 to 7 foot seas to our waters.
The weekend should start out fairly benign but an approaching
frontal boundary will bring deteriorating conditions by Saturday
night or Sunday.
Fire weather...we are still expecting humidities to drop to near 35
percent over Levy County Thursday afternoon as a cooler and drier
airmass moves by mostly to our north. Otherwise...no fire weather
Preliminary point temps/pops...
tpa 80 64 77 56 / 10 10 20 10
fmy 85 66 81 60 / 10 10 20 10
gif 81 63 74 53 / 10 20 20 10
srq 81 64 79 59 / 10 10 20 10
bkv 79 60 74 47 / 10 20 20 10
spg 78 66 74 59 / 10 10 20 10
Gulf waters...Small Craft Advisory until 10 am EST this morning for
Englewood to Tarpon Springs out 20 to 60 nm-Tarpon
Springs to Suwannee River out 20 to 60 nm.
Short term/marine/fire weather...jillson