Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jacksonville Florida
333 am EDT Friday Aug 28 2015
Near term /today and tonight/...
Early this morning...so far moisture surging back to the north has
triggered most of the convection over the Atlantic coastal waters and
some may brush the coastal counties with the best chances of
moving onshore across southeast Georgia with brief heavy rainfall
in some bands that move onshore there. Further inland...a few
isolated showers possible...otherwise fair skies with very little fog
formation expected this morning.
Today...abundant tropical moisture with precipitation water amounts close
to 2 inches over the central/southern Florida Peninsula will begin to surge
back to the north across NE Florida/coastal southeast Georgia this morning and inland
southeast Georgia by the afternoon hours. While southerly flow is expected
aloft...the surface flow will be out of the east which will bring
showers and thunderstorms onshore along the coastal counties
first...then developing over inland areas by the afternoon with
daytime heating. With onshore flow and abundant cloud cover expect
slightly below climatology temperatures in the middle/upper 80s along the coastal
counties and near 90 degrees further inland. The evening soundings
showed some decent cooling in the middle levels with 500 mb temperatures in
the -8c to -10c range...which is rather cool for late August so
expect high chances for shower activity to contain embedded
convection throughout the day. The slow movement inland will make
the primary threat heavy rainfall if any training rain bands can
set up along the coast...while further inland during the afternoon
hours expect greater chances for storms with gusty winds and even
some small hail due to the cool middle level temperatures...although just a
few strong storms are expected.
Tonight...with loss of daytime heating the inland areas should see
convection decrease and end by midnight while the east/southeast steering
flow off the Atlantic will continue scattered showers/storms over the
Atlantic coastal waters which will move onshore at times through the
night. Near normal lows in the 70s expected.
Short term /Saturday and Sunday/... low level flow will coincide
with southerly flow aloft to set the stage for an active
thunderstorm pattern over the weekend. Scattered to numerous storms
are expected both days. Maximum temperatures will be a little lower with highs
generally in the middle to upper 80s with the lower readings at the
coast and the higher readings well inland.
Long term /Monday through Thursday/...
despite settling with a forecast that somewhat reflects the current
track from the Tropical Prediction Center (just off our Atlantic
coast early next week)...the forecast for early next week continues
to be one of extremely low confidence and changes can be
expected...probably sooner rather than later...especially given the
latest westward shift in the model suite.
Rainfall amounts...wind conditions...and temperatures early next
week will all depend on the eventual evolution of Erika...if it
survives Hispaniola. As of the 0z model runs tonight...there remains
a considerable amount of spread with regards to exactly what this
system has up its sleeve early next week. The latest GFS and nearly
all of its ensemble members have now trended westward...taking the
system across the southern tip of the Florida Peninsula and into the
Gulf of Mexico. The NAM and European also show this. Given the
latest trends with this system...this shift seems rather reasonable.
Based on the high degree of uncertainty...it is still a little too
soon to provide specific forecast details for early next week. In
the meantime...we still have plenty of time to monitor the progress
of this system over the next couple of days. Erika...which is
currently a weak and disorganized tropical storm...still has to
contend with persistent wind shear...dry air...and the mountainous
terrain of Hispaniola over the next 36 to 48 hours. Exactly
how...if at all...this system emerges on the other side of all of
this adversity...should allow US to attain a much better assessment
of how the system will impact our area...thus allowing US to provide
a more confident forecast.
Even with a system tracking west of our area...a plume of rich
tropical moisture will move into our area and bring periods of heavy
rainfall with potential for localized flooding concerns during the
first half of next week.
current shower activity over the Atlantic coastal waters and pushing
to the north/northwest and may impact ssi at times early this morning
otherwise will wait for onshore push of convection during the
morning hours to impact taf sites from the coast and moving inland
to kvqq and kgnv by the late morning and afternoon hours. For now
have mainly included vcsh until around 15z...then enough heating
should occur and have changed it to thunderstorms in the vicinity through the remainder of
the day until around 00z...then back to vcsh. Just not organized
enough rainfall to warrant tempo groups with probability of precipitation generally in the
40-60% range. Mainly VFR ceilings today...with possible MVFR
ceilings/visibilities in heavier shower activity that may impact some of the
terminals. Easterly winds increase to around 8-12 kts with gusts
to 15-18 kts along the coastal taf sites.
onshore flow expected to increase to 10-15 knots with seas into
the 3-5 feet range by Sat...with further increases on Sunday
possibly to scec conds. Early next week...still too much
uncertainty in long range predictions of Erika and potential for
high winds/seas for any details and will continue with wording for
tropical storm conditions possible based on current wind probs at
this time and any changes will depend on TPC track updates in the
next couple of days.
Rip currents: easterly flow increases just enough today and
Saturday to warrant a marginal moderate risk of rips with swells
of 2 to possibly 3 feet at times.
Surf zone/tides: coming up on full moon Sat 8/29 and expect the
easterly flow to enhance already elevated tidal levels along the
coast but not likely enough to produce coastal flooding at this
Preliminary point temps/pops...
amg 90 72 87 72 / 40 30 60 40
ssi 85 77 85 75 / 50 40 50 40
jax 88 74 87 73 / 50 30 60 40
sgj 87 75 86 75 / 50 40 50 30
gnv 90 72 88 71 / 60 40 60 30
ocf 90 73 89 72 / 70 40 60 30