Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jacksonville Florida
419 am EDT Friday Jul 29 2016
..near record highs expected again this afternoon...
overnight surface analysis depicts Atlantic ridging (1017
millibars) centered east of the Bahamas, with is axis extending
across central Florida. Aloft...deep-layered riding remains in
place over the Florida Peninsula. Fair skies prevail over our
region, with light southwest surface winds keeping muggy
conditions in place. Temperatures at 08z ranged from the mid 70s
well inland to the lower 80s in coastal locations, with dewpoints
in the 70s.
Near term (through saturday)...
deep-layered ridging will remain centered just off the Florida East
Coast, with its axis extending across central Florida. This weather
pattern will create southwest to west winds around 10 knots
throughout the lower and mid levels of the atmosphere, which
will keep the Atlantic sea breeze pinned near the coast during the
early afternoon hours. A mostly dry and subsident air mass with
unseasonably warm mid-level temperatures will prevail throughout
our area, resulting in below average rain chances and near record
highs once again this afternoon. The 00z operational GFS and European model (ecmwf)
models indicate that a pocket of higher precipitable water air will rotate
around the western periphery of the deep layer ridge from central
Florida this afternoon into north central Florida early this evening. This
feature should ignite convection along the Gulf Coast sea breeze
by early afternoon, with isolated to widely scattered
thunderstorms developing over southern Marion County towards noon.
Activity will move slowly east-NE across the rest of Marion and into
Putnam County by late afternoon, where it may collide with the
Atlantic sea breeze towards sunset near the St. Johns River along
the Putnam/Flagler County border. Some isolated convection may try
to develop northward along the St. Johns River through the early
evening hours as outflows from this activity collide with the
Atlantic sea breeze. Highs will reach the upper 90s inland, with
mid 90s expected at the beaches. Dry air will mix down to the
surface during the afternoon hours, keeping Max heat index values
around 105 degrees.
Any lingering isolated convection along the St. Johns River basin
and north central Florida will quickly diminish by the mid-evening
hours. Lows tonight will range from the mid 70s inland to near 80
at the coast.
Ridging aloft will begin to slowly retrograde on Saturday as a
TUTT/weak low level trough progresses westward across the Bahamas.
Temperatures aloft will remain warm for this time of the year (-4
to -5 celsius at 500 millibars), but deep-layered moisture will
increase slightly from south to north as the day progresses. The
weakening ridge will allow the Atlantic and Gulf sea breezes to
advance inland a little earlier than today, and these boundaries
should be the focus for isolated to widely scattered convective
development during the afternoon hours for most of our region. A
light westerly steering flow may result in a sea breeze collision
near the St. Johns River and I-95 before sunset, with activity
migrating slowly westward towards coastal locations towards
sunset. Inland highs will soar into the mid/upper 90s, with mid
90s again at the beaches before the sea breeze pushes inland. Max
heat index values will again approach 105 degrees.
Short term (saturday night through monday)...
surface high pressure ridge will be east of the region this
period, with a trough of low pressure to the north. This pattern
will result in a fairly moist southerly flow, leading to scattered
afternoon convection across the forecast area.
Temperatures will remain above seasonal averages this period.
Long term (monday night through thursday)...
high pressure will be southeast of the region with a trough to the
northwest this period. The combination of a moist flow and the
proximity of the trough will result in scattered afternoon
convection across the forecast area.
Temperatures will be near to slightly above normal this period.
VFR conditions will prevail at the regional terminals. Isolated
thunderstorms may approach gnv after 21z through 01z. The Atlantic
sea breeze will move slowly inland through the afternoon hours,
crossing sgj around 18z, ssi around 19z, crg around 20z, jax
around 21z, and vqq around 23z. Surface winds will become
southeasterly at 10-15 knots after the sea breeze passes these
terminals...and will then veer to a southerly direction with
slowly decreasing speeds towards 00z.
evening southerly wind surge has brought speeds into the caution
range offshore. Winds will veer to a southwesterly direction
during the predawn hours, with speeds gradually decreasing below
15 knots. Winds during the morning hours will generally be
westerly around 10 knots, with the sea breeze developing in the
near shore waters. Winds will become southeasterly near shore,
with speeds increasing to near 15 knots during the afternoon, with
southerly winds closer to 10 knots expected offshore. Another
evening wind surge will bring south to southwest winds up to near
caution speeds offshore shortly after sunset. Winds overnight will
become southwest to westerly with gradually decreasing speeds. A
similar weather pattern will prevail on Saturday, with a southerly
wind pattern prevailing during the daylight hours Sunday through
midweek, with evening wind surges resulting in southwesterly winds
reaching the caution range offshore on Sunday night and possibly
each evening early next week. Only isolated thunderstorms, mainly
during the late afternoon and evening hours, are expected through
the weekend, with slowly increasing coverage expected early next
Rip currents: low risk expected through the weekend.
record highs for today (7/29):
Jacksonville 100 (1875)
Gainesville 99 (1896)
St. Simons Island 99 (1993)
Alma 99 (1993)
Preliminary point temps/pops...
amg 98 74 98 74 / 10 0 30 30
ssi 96 80 95 80 / 10 10 20 20
jax 98 75 97 76 / 20 20 30 30
sgj 95 78 94 78 / 20 10 20 30
gnv 97 74 95 74 / 20 10 40 20
ocf 96 74 94 75 / 30 20 40 20