Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Tampa Bay Ruskin Florida
843 PM EST Friday Feb 5 2016

Update (overnight through saturday)...
01z water vapor and h4 rap analysis shows an amplified upper level
pattern in place over the Continental U.S. This evening. Northern stream flow
forms a steep longwave ridge over the western states...before
diving quickly back to the south into a sharp progressive longwave
trough through the middle-section of the country. The flow then
finally ridges back up into the Appalachians in the wake of
storminess exiting the northeastern states. The trough through the
middle-section the County will keep our forecast changing through the
weekend as it approaches and passes over the state. Embedded
within the base of this trough we find a strong piece of shortwave
energy pivoting over the Southern Plains. This shortwave will
cross the northern Gulf during Saturday and arrive over our head
Saturday night. Models are in good agreement that the strong
energy passing over the warmer baroclinic waters of the Gulf
Stream will promote surface cyclogenesis near the Southeast
Florida coast Saturday night. This low will then quickly migrate
to the northeast into the western Atlantic...while becoming quite
a large and potent ocean storm during Sunday/Sunday night. More on
some potential impacts from this system to our area Saturday below...
but first lets look at the forecast for the overnight period.

The atmosphere sure has dried out in the past 24 hours in the wake
of the upper trough the crossed the region last night. Precipitable water values
last night were near record levels for this time of year...and now
are running near record lows. The 00z ktbw sounding this evening
came in with an extremely low precipitable water value of only 0.15". This is
pretty dramatic given that the 10th percentile value for the date
is around 0.40". This is a very dry troposphere under any
circumstances. Viewing the sounding confirms the precipitable water numbers with
very large dewpoint depressions through the entire extent of the
column above the boundary layer. As would be expected with this
profile and no synoptic lift to speak of...that our skies are
clear this evening. However...there are some clouds down over far
South Florida...and these will begin to slowly move back to the
north with a general moisture surge later tonight and continuing
through the daylight hours of Saturday. However...for the
overnight hours...the forecast will be rain-free for all zones
with seasonable cool temperatures.

Strong shortwave will dig southeast into the northern Gulf during
Saturday with height falls commencing over the Florida Peninsula
during the second half of the day. Skies will continue to cloud
over as low level warm air advection regime ahead of this system becomes more
defined. Generally speaking...the first half of the day looks
dry...with perhaps a few light showers/sprinkles south of the I-4
corridor. However...by the second half of the day...the more
robust synoptic support for lift/deep layer qg forcing and upper
diffluence will begin to line up over the region. Even with some
fairly healthy dynamics for lift...the moisture through a deep
layer will not be all that favorable. Therefore...although the
dynamics might normally suggest a healthy rainfall event...this
one is likely to not live up to anything more than a scattering
of afternoon/evening mainly light showers across the region. The
best coverage of these showers should exist south and southeast
of the I-4 corridor. Overall rainfall amounts across our zones
look to be on the light side. Late in the day / evening...the
surface low will begin to consolidate just off the Florida East
Coast. As this low wraps up Saturday night...should see the
showers move east of our region with the flow around the storm
bringing drier air back down from the northwest on gusty winds.

By Sunday the rapidly deepening storm will be exiting away from
the peninsula into the Atlantic...with a dry...cool...and breezy
day on tap to end the weekend.

&&

Aviation...
VFR conditions prevail across west-central and southwest Florida
this evening. Will see a slow increase in clouds during the second
half of the night from south to north. Potential will exist for
ceilings between 3-5kft by dawn...especially for kpgd/kfmy/frsw. Have
gone with prevailing MVFR 2-3kft ceilings with scattered light showers for
Saturday afternoon and evening. MOS restrictions are lower but
seem overdone for the pattern. Will continue to monitor and adjust
with future forecasts.

&&

Marine...
residual seas will gradually subside below advisory levels
overnight. An area of low pressure will develop off the East
Coast of Florida Saturday night and move rapidly northeast over
the open Atlantic on Sunday. Winds are expected to increase back
above advisory levels in the wake of this system Saturday night
into Sunday. Another cold front will move across the waters on
Monday...however very little shower activity if any will be
associated with the cold front. Winds again will likely increase
above advisory levels late Monday and persist through Tuesday.

&&

Preliminary point temps/pops...
tpa 47 64 46 58 / 10 30 30 10
fmy 52 72 51 61 / 10 40 50 10
gif 49 68 45 59 / 10 40 50 10
srq 49 65 50 58 / 10 40 30 10
bkv 43 63 41 58 / 10 30 40 10
spg 50 63 49 57 / 10 30 30 10

&&

Tbw watches/warnings/advisories...
Florida...Beach hazards statement through Monday evening for coastal
Charlotte-coastal Lee-coastal Manatee-coastal
Sarasota.

Gulf waters...Small Craft Advisory for hazardous seas until 4 am EST
Saturday for coastal waters from Bonita Beach to
Englewood Florida out 20 nm-coastal waters from Englewood
to Tarpon Springs Florida out 20 nm-coastal waters from
Tarpon Springs to Suwannee River Florida out 20 nm-waters
from Bonita Beach to Englewood Florida out 20 to 60 nm-
waters from Englewood to Tarpon Springs Florida out 20 to
60 nm-waters from Tarpon Springs to Suwannee River Florida
out 20 to 60 nm.

&&

$$

Update/aviation/marine...mroczka
decision support...rude
upper air/data quality control...Davis

National Weather Service Glossary of Abbreviations