Scientific Forecaster Discussion
fxus62 kmlb 180805 aac
Area forecast discussion...updated
National Weather Service Melbourne Florida
405 am EDT Fri Aug 18 2017
Today...upper low will move from central to western Cuba while the
axis of a mid to upper level inverted trough extends northward into
central Florida. The models show high moisture lingering today to
the north of the low level ridge axis which will nudge north into
the Central Peninsula. Some drier air aloft, seen on water vapor
imagery across the northern Bahamas, will start to affect southern
sections. Therefore, pops in the north look to be around 60%,
with 30 percent over the south.
Impressive upper level winds out of the east are occurring to
the north of the low, with 250 mb speeds around 50 knots forecast
over our southern areas. Additionally, some drier and cooler mid
level air associated with the trough aloft is shown affecting
southern sections. Though a lower coverage is anticipated in the
south, some more vigorous storms with strong gusty winds are
Sat-sun...as mid-upper low over Yucatan Channel moves slowly west,
the associated low-level reflection of an inverted trough moves
across South Florida late Sat/early sun. West of trough axis, expect
brief lowering of deep-layer moisture for Sat, reducing pops to
below mid August normals, especially north/central County Warning Area. Temps will
run a few degrees above climo. Slug of deep, tropical moisture
advects from southeast to northwest across County Warning Area to east of trough axis Sat night
and sun. With deep southeast flow of moist conditions (pw 2.00-2.25
inches), coverage of showers with embedded storms will increase
over the Atlantic late Sat with scattered activity working
onshore, especially southeast coast, with some isolated nocturnal
showers possible even far inland. High coverage of showers/storms
expected sun areawide, with best chance over central/South County warning area
Mon-Thu...ridge axis re-establishes north of County Warning Area next week,
resulting in long fetch of onshore flow across central Florida.
Moisture levels lessen early in the week as inverted trough exits
west, causing diurnal storm coverage to return to climo values
(generally 30-40 pops, possibly a little higher near Lake
Okeechobee and southern Treasure coast). Global models continue
to display run-to-run inconsistency with handling of next
tropical disturbance. With unfavorable conditions for significant
development, best course of action at this point is to show
increase of shower/storm coverage Wed/Thu as swath of higher precipitable water
reaches area in association with inverted trough. Max temps near
to slightly above normal, with mins at least several degrees above
climo, with some coastal locations remaining near 80 for mins
given onshore flow across warm waters.
Aviation...VFR until this afternoon when scattered storms break
out. The greatest chance for direct impacts on terminals will be
across the interior and at kdab. The main hazards will be IFR
conditions in heavy rain and frequent lightning strikes, but gusty
winds to 40 mph are possible. Convective initiation along the
East Coast sea breeze should be just inland from kmlb to ksua.
Storms may be more gusty there, so outflow boundaries could still
kick up winds at some of those terminals.
today-tonight...axis of Atlantic high pressure ridge is forecast to
nudge north into the central waters. This will maintain a rather
light pressure gradient with winds generally 10 knots or less today
then a period of 10-15 knot southerly flow is expected across the
central/north waters this evening. Still, seas will only be 1-2
feet along the coast and 2-3 feet well offshore. Scattered strong
afternoon storms over land may kick gusty outflow boundary winds
back to the immediate coast, mainly around Cape Canaveral and
Sat-sun...light southeast winds increasing to 10-15 kt, especially across
southern waters late Sat/early sun as axis of inverted trough
reaches South Florida. Seas 2-3 ft, up to 4 ft in Gulf Stream.
Scattered to locally numerous showers and storms moving onshore,
especially southernmost waters.
Mon-Tue...long southeast fetch near 15 kt with seas building to 4-5 ft,
except 3 ft over northern near-shore waters. Onshore flow becomes
more easterly Tue and perhaps lessing a bit as ridge axis builds
far to the north. Long fetch should allow seas to remain elevated
at 4-6 feet across offshore waters and 3-4 ft closer to shore.
Scattered onshore moving showers/storms.
Preliminary point temps/pops...
dab 91 76 90 77 / 50 20 30 30
mco 94 76 93 76 / 50 20 30 20
mlb 91 78 89 78 / 30 20 20 30
vrb 92 76 89 77 / 20 10 30 40
Lee 93 77 93 77 / 50 20 30 20
sfb 94 77 93 77 / 60 20 30 20
orl 94 77 93 77 / 50 20 30 20
fpr 92 76 89 77 / 20 20 30 40