Scientific Forecaster Discussion
fxus62 kjax 150801
Area forecast discussion
National Weather Service Jacksonville Florida
401 am EDT sun Sep 15 2019
..strong onshore winds with high/rough surf through the
Near term (today-tonight)...
tc Humberto over the wrn Atlantic near 28n77.5w continues to
slowly push north-northwest while fairly deep northeast flow up to
around 3-5 km affects our region. Best moisture is over the far
south and eastern zones (pwats 1.9-2 inches), with low level
convergence and a couple of rain bands on the outer parts of
Humberto rotating through the southeast parts of the forecast
area. Latest radar shows isolated to scattered showers over the
marine waters, and narrow bands of showers pushing into northeast
FL, generally fading past Highway 301. Best chances of rain today
will be for the southeast zones with a forecast of 40-60 percent
coastal northeast Florida and 20-40 percent for inland northeast Florida and
only 20 percent for southeast where moisture is just enough to
support a couple of lone showers by the aftn. Chance of T-storms
is fairly low given relatively weak instability with SBCAPE under
2000 j/kg. Max temps today near 90 inland, and mid 80s at the
coast due to more cloudiness and shower activity. Winds today will
increase to 15-20 mph with a few gusts up to 30 mph, especially
for northeast Florida and coastal southeast Georgia. For the time being,
appears winds stay just below wind advy criteria but will be
monitored. For tonight...we continue to advertise a chance of
showers for the coastal counties but as the low level wind field
backs, some drier air will filter in and the prospects for showers
will diminish for the inland areas of northeast Florida. Lows may dip
to near 70 over inland southeast Georgia but rest of the area expected
to have lows from 72 to 78 deg.
Short term...Monday through Wednesday...
Low level ridging will continue to sit over southeastern Continental U.S. And
Humberto will continue to move further out into the Atlantic, keeping
northeasterly winds in place across the area. At the upper levels,
a ridge of high pressure will remain off to our west, with a
trough axis stretching across the northern Gulf waters, and
another ul trough over the northeastern Continental U.S.. relatively light
will prevail aloft, but with a northerly component to the winds
throughout much of the atmospheric column, we'll see a drier air
mass work its way south into the area. Model precipitable water values below 1.5"
dig into southeast Georgia and NE Florida Monday night. Expect mostly dry conditions
with 20-40% chances for showers and isolated thunderstorms along
the coast. Temperatures will peak in the mid 90s Monday and Tuesday,
lower 90s on Wednesday. Lows will be mostly in the low 70s.
Long term...Thursday through sun...
Deep layer ridging will slowly push eastward through the end of the
work week. By Thursday-Friday, this high pressure to our north may
set up a wedge pattern with an air mass from the Appalachian Mountains
moving down into S Georgia. Pops will be low through the long term,
with 20-40% chances for showers and isolated thunderstorms, again
mostly along the coast. Temperatures will be cooler, with highs in
the mid-upper 80s and lows in the upper 60s to low 70s.
Periods of MVFR cigs are expected for the tafs through this
morning, with lowest chance of MVFR at gnv. A few showers are to
be expected for sgj...crg...vqq and jax. Lower chances for
jax and ssi...and MVFR vsby possible. Breezy northeast winds
at sgj early this morning...but winds will pick up again
by mid morning from the northeast at about 15g25kt. Some improvement
in clouds expected after about 20z-21z today into this evening
but still a threat of MVFR cigs for sgj into Sunday night due to
north-northeast flow over the Atlantic waters.
Winds and seas remain very hazardous for small boaters with solid Small Craft Advisory
in place. Northeast winds 20-25 kt and some occasional gusts up
to 35 kt expected through tonight and early Monday. Winds and seas
may decrease a bit on Tuesday-Tuesday night but we see winds
increasing again late Wed through Thu as high pressure ridge
builds north of the area and winds pick up again to near 20 kt and
seas upwards of 5-8 feet. Swells from Humberto should continue to
affect area waters at least through late this coming week.
Rip currents: high risk of rip currents expected in the rough surf
conditions and surf/breakers of 5-7 ft range along the northeast
Florida coast and high surf advisor in effect, with 4-6 ft surf
expected along the southeast Georgia coast. Elevated water levels
expected along the St Johns River basin/Atlc coast during time of
high tide with departures around 1 ft above predicted tide levels
but this will continue to remain just below minor flood levels.
Borderline high dispersion indices are anticipated this afternoon across
inland portions of southeast GA, with more widespread dispersion indices
in the 75-85 range expected tomorrow. Moderate north-
northeasterly transport winds are forecast both days, but winds
will lower on Tuesday. Relative humidity values will remain above critical
thresholds through Monday, then drier air will begin to move in on
Tuesday. The drier air and higher winds will not occur at the
same time, so no red flag conditions are forecast.
Preliminary point temps/pops...
amg 91 72 93 70 / 10 0 10 0
ssi 87 76 88 75 / 30 20 20 10
jax 88 75 90 73 / 40 20 10 10
sgj 86 76 88 74 / 60 30 30 10
gnv 89 73 91 71 / 30 10 10 0
ocf 90 73 92 72 / 40 10 10 0
Florida...high rip current risk through Monday evening for coastal Duval-
coastal Flagler-coastal Nassau-coastal St. Johns.
High surf advisory until 4 am EDT Monday for coastal Duval-
coastal Flagler-coastal Nassau-coastal St. Johns.
Georgia...high rip current risk through Monday evening for coastal Camden-
Am...Small Craft Advisory until 10 PM EDT Tuesday for waters from
Altamaha Sound Georgia to Fernandina Beach Florida from 20 to 60 nm-
waters from Fernandina Beach to St. Augustine Florida from 20 to
60 nm-waters from St. Augustine to Flagler Beach Florida from 20
to 60 nm.
Small Craft Advisory until 9 PM EDT Monday for coastal waters
from Altamaha Sound to Fernandina Beach Florida out 20 nm-
coastal waters from Fernandina Beach to St. Augustine Florida
out 20 nm-coastal waters from St. Augustine to Flagler
Beach Florida out 20 nm.