Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Miami Florida
issued by National Weather Service Tampa Bay Ruskin Florida
928 am EDT Monday Jul 25 2016
an upper level low over the eastern Gulf of Mexico early
this morning will continue to move west-northwest toward the
northern Gulf Coast later today on the western side of the sub-
tropical ridge over the Atlantic. Morning radiosonde observation data shows a moist
and unstable air mass covering the forecast area with a precipitable water of 2
inches and lifted indice's in the -4 to -5c range. 88d returns show some
isolated showers over the Atlantic waters, otherwise dry
conditions under mainly clear skies prevailed across the forecast
area. As for the rest of today expect to see a gradual increase in
showers and storms along the East Coast sea breeze boundary by
late morning and early afternoon, with the highest probability of precipitation and
coverage of storms expected over inland and western sections of
the forecast area during middle to late afternoon along the east and
West Coast sea breeze merger. Warmer middle level temperatures (-5.5c
at 500mb) should keep overall storm intensity in check with a low
severe threat, with locally heavy rains, some gusty winds, and
frequent deadly lightning strikes being the main hazards from the
storms as they move to the west and northwest around 10 miles per hour. Have
made some minor adjustments to rain chances in the grids, but
overall change does not warrant a morning update to the zones at
surface high pressure from the western Atlantic extending west
northwest across the Northern Peninsula and southeastern states will
maintain east to southeast winds around 10 knots with seas of 2 to 3
feet with little to no swell expected over the Atlantic and Gulf
waters the remainder of today. Winds and seas will be higher near
thunderstorms, otherwise no headlines are expected. Current forecast
is on track with no real changes expected in the late morning update.
Rip current risk will be low today for the Atlantic and Gulf
beaches, but may increase some by midweek with an increasing east
southeast onshore flow for the Atlantic beaches.
Previous discussion... /issued 754 am EDT Monday Jul 25 2016/
today looks less active than the last couple of days for the area
around the taf sites. There may be shower development by late
morning along the coastal areas, as a sea breeze attempts to
develop. The sea breeze should not be too strong today, and likely
not progress too far inland. The showers will propagate through
outflow boundaries, and most of the activity should be in the
interior this afternoon. However, there is still a slight chance
amendments may be needed for vcts, at any of the taf sites.
Otherwise, VFR conditions through the taf period, with brief IFR
under any heavy showers that develop.
Previous discussion... /issued 330 am EDT Monday Jul 25 2016/
Surface high pressure and upper-level ridging will prevail over
South Florida over the next several days, with a east to southeast
flow. A tropical wave currently located in the central Atlantic will
continue to track westward, approaching the region by the end of the
Near term /through 6pm Monday evening/...
As of 330 am EDT...a quiet night will continue across the region
as drier air continues to advect westward from the Bahamas. This
drier air has resulted in partly cloudy to mostly clear skies for
much of the region. An isolated shower will be possible over the
local Gulf and Atlantic waters through daybreak, with dry weather
for land areas.
Today should see less in the way of coverage of showers and
thunderstorms, as the aforementioned dry air continues to spread
across South Florida. This dry air is on the leading edge of a sal
intrusion, with hints already evident on the 00z Nassau, Bahamas
sounding with a drying column in the 850-700 hpa layer along with a
sharp capping inversion.
Despite drier air working into the region, enough residual low-level
moisture should be in place to allow for scattered showers/storms to
develop mainly during the afternoon and evening hours, with some
isolated activity possible by the late morning on the leading edge
of the Atlantic sea breeze. With the flow out of the east/southeast
and slightly stronger than recent days, the best coverage will be
across the interior and Gulf Coast, especially across inland
Collier, Glades, and Hendry counties.
The primary threats with today's storms will be frequent lightning,
gusty winds up to 40 mph, and locally heavy rainfall. The threat for
strong storms today will not be as high as recent days, with 500 hpa
temperatures warming back to near normal values. The wild card will be how
much dry air intrudes during the afternoon which may enhance dry air
entrainment in updrafts for some stronger gusty winds in the 40-55
miles per hour range.
High temperatures will generally range from near 90 to lower 90s,
with a few middle 90 readings possible in the interior. Heat index
readings will be near 100 degrees for most areas, but as
high as 105 degrees in portions of the interior and Gulf Coast.
Short term /6 PM Monday evening through Tuesday night/...
Below normal chances for showers/storms expected through midweek...
Heat indices 105+ degrees across portions of interior and Gulf
Monday night: any lingering convective activity is expected to
rapidly diminish after sunset, with a stray shower/rumble of thunder
possible out over the local Gulf waters through the nighttime hours.
Low temperatures will range from the middle 70s in the interior to near 80
along the coasts.
Tuesday-Tuesday night: the aforementioned sal layer will continue to
drift westward into South Florida, with the latest model guidance
depicting 1000-500 hpa relative humidity falling below 50% by Tuesday afternoon.
Forecast model soundings also show a strong capping inversion around
850 hpa at the base of the sal layer, along with 500 hpa temperatures above
normal (around -6 to -7 c). All of these features will suppress
precipitation chances across South Florida Tuesday, with much of
South Florida likely seeing the first dry day in quite some time.
The best chance for some widely scattered showers/storms will be
across the interior.
High temperatures on Tuesday will be a few degrees warmer with
plenty of sunshine expected, ranging from the low 90s to middle 90s.
Heat indices will range from 100-105 degrees across much of inland
South Florida, with 105+ degree readings across portions of the
interior and Gulf Coast. Will continue to monitor for the potential
issuance of heat advisories on Tuesday and highlight in the
hazardous weather outlook. Low temperatures Tuesday night will
range from the middle 70s to near 80.
Long term /Wednesday through Sunday/...
Below normal precipitation chances continue through at least
Heat indices 105+ degrees across portions of interior and Gulf Coast
Wednesday-thursday: this period of the long term will continue to
feature below normal precipitation chances with dry air firmly
entrenched across the region. The best chance for widely scattered
showers/storms will be across the interior and Gulf Coast. Heat
indices will once again range from 100-105 degrees across much of
inland South Florida, with 105+ degree readings across portions
of the interior and Gulf Coast.
Friday-sunday: midlevel moisture begins to return by Friday,
allowing for a return to normal chances for precipitation featuring
scattered afternoon/evening showers and thunderstorms focused in the
interior and Gulf Coast. A tropical wave passing by may also help to
enhance activity as well during this period.
Temperatures will be near normal during the long term period.
Preliminary point temps/pops...
West Palm Beach 91 80 92 82 / 30 10 10 10
Fort Lauderdale 90 81 91 81 / 30 10 10 10
Miami 90 80 92 80 / 30 10 10 10
Naples 90 76 91 77 / 40 20 20 20