Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Miami Florida
916 am EDT Sat Jul 23 2016
for this mornings update, have consulted the 12z sounding as well
as the current hi-res models. Today is looking not as favorable
for strong convection as yesterday. A 500mb ridge is moving over
the region, and the sfc high is residing near Bermuda at this
time. Looking at the 500mb temps, they have warmed back to around
-6.7c this morning, and pwats have dropped back to 1.87 inches.
700mb-500mb lapse rates are only 5.8 c/km this morning, and even
the freezing level is back to just over 15k ft. The surface flow
is much lighter as well. All, this looks to be more of a diurnal
and sea breeze driven convective activity today. The hrrr is
showing most convective development should hold off until at least
17z, barring a few isolated showers between now and then. It then
develops most of the convection along the Atlantic coast sea
breeze boundary. This is not contrary to the area of activity in
the gfs20, nor really the European model (ecmwf). So, have backed off on pops this
morning, and adjusted this afternoons pops to favor areas inland
from the coast (reducing pops along the immediate Atlantic coast).
However, this does not mean there will be no convective activity
along the coast, but most of it should be west of the area,
perhaps over the central to western Southeast Florida Metro areas,
then slowly progressing westward. For the Gulf Coast, a similar
situation, with most of the convective activity developing along
the Gulf Coast sea breeze, and mainly affecting areas east of i75,
and progressing eastward into the interior.
With the warmer temps aloft, even small hail will be hard to come
by. There is almost no shear in the low levels, leaving only some
gusty wind as the threat besides the typical heavy rain and
lightning. The storm motion is only showing to be around 3 kts
today, so it may very well resemble yesterday where, what
develops, pretty much remains in place for a while. This could be
a problem if the convection is over any of the Metro areas, and
not the interior, as there could be ponding of water on roadways,
and typical low drainage areas.
Previous discussion... /issued 759 am EDT Sat Jul 23 2016/
with an upper level ridge sitting to the northwest, and a surface
Bermuda high settling in, todays activity should be mostly sea
breeze driven. Current models are showing convection initiating
after 17z along the Atlantic coast, with mainly showers. As the
East Coast sea breeze slowly progresses inland, additional
convection should develop, and likely mature into thunderstorms
along the sea breeze boundary. For this mornings runs of the
models, most of any thunderstorm activity looks as though it
should be west of the taf sites, outside of the 10sm ring. Given
that, have taken out the thunderstorms in the vicinity in exchange for vcsh, until more
confidence can be had for the ts coverage closer to the airports.
Otherwise, will still expect tsra, but more towards the interior
today, with isolated ts closer to the East Coast. For kapf, models
are showing the activity should be east of the site, so, also
reduced down to vcsh for now.
Previous discussion... /issued 346 am EDT Sat Jul 23 2016/
At the surface, high pressure and a light easterly flow will prevail
over South Florida through the weekend. Aloft, strong upper-level
ridging will continue across the central United States while an
upper-level trough off the eastern Seaboard gradually weakens. In
the tropics, a tropical wave will continue to move westward through
the central Carribean.
Near term /through 6pm Saturday evening/...
Another round of scattered to numerous thunderstorms expected across
much of South Florida today...
As of 345 am EDT...a quiet and dry weather night across South
Florida and the local waters will continue after an active day of
convection yesterday, outside of some possible widely scattered
showers and storms over the Atlantic waters. Light and variable
winds across many inland areas has allowed for plenty of remnant
outflow boundaries to persist, which will help to focus convection
later this morning and continuing into the afternoon and evening
hours as both Atlantic and Gulf sea breezes develop and collide.
Similar to yesterday, expect scattered showers and thunderstorms to
develop by the late morning hours along the Atlantic sea breeze and
portions of the interior, becoming numerous into the afternoon
hours, especially across the interior as the Gulf sea breeze pushes
inland. While the bulk of the activity will be in the interior, the
lingering presence of a weakening upper-level trough and light wind
field will allow for convection to occur anywhere across South
Florida, strongest where sea breeze/outflow boundary collisions
The primary threats with the strongest thunderstorms will be
frequent lightning, gusty winds up to 50 mph, and heavy rain.
Waterspouts will also be possible over the nearshore waters as well,
with plenty of boundaries and the weak low/midlevel wind field in
High temperatures will be near normal, ranging from near 90 along
the East Coast, to lower and mid 90s in the interior and Gulf Coast.
Heat indices will once again top 100 degrees at times during the
late morning/afternoon hours, mainly across the interior and
portions of the Gulf Coast prior to sea breeze development.
Short term /6 PM Saturday evening through Sunday night/...
Saturday evening/night - shower and thunderstorm activity will
continue into the early evening hours, lingering mainly across the
interior, Gulf Coast, and Lake Okeechobee region. During the
overnight hours, typical diurnal trends should ensue with mainly dry
conditions over land and isolated to scattered showers/storms over
the local waters. Low temperatures will range from the mid 70s to
Sunday/Sunday night - another day of more widespread coverage of
showers and thunderstorms is expected across South Florida as a
tropical wave continues to pass south of the region across the
Carribean. The best chance for showers/storms will be during the
afternoon/evening hours across the interior and Gulf Coast, with the
Atlantic sea breeze becoming slightly stronger than in recent days.
Will need to keep an eye on the inland extent of the Gulf sea
breeze, which may help to focus additional convection into portions
of the East Coast Metro.
Showers and thunderstorms will decrease in coverage during the
evening hours, with land areas mainly dry through the nighttime
hours and additional scattered convection possible mainly over the
local Atlantic waters. High temps Sunday will range from the upper
80s to lower 90s with lows Sunday night ranging from the mid 70s to
Long term /Monday through Friday/...
The long term period will feature mainly afternoon and evening
scattered showers and thunderstorms, with a continued
east/southeasterly flow keeping the bulk of the activity across
the interior and Gulf Coast. Hints of a weak sal intrusion will be
possible early next week, which may limit overall convective
coverage somewhat. The aforementioned tropical wave will continue
to progress westward into the western Carribean by the midweek
Temperatures will be near normal for late July during the long term
A light easterly flow will prevail across the local Atlantic and
Gulf waters through the weekend, generally around 10 knots or less.
Locally higher winds will be possible in and around thunderstorms,
along with frequent lightning and rough seas. Seas are expected to
be 3 feet or less with little to no swell. The easterly flow will
begin to increase and shift more southerly heading into next
week, with minor increases in seas possible, but still expected to
be 3 feet or less.
Rip current risk will be low through the weekend for Atlantic and
Gulf beaches with a light easterly flow in place.
Preliminary point temps/pops...
West Palm Beach 89 74 88 76 / 30 20 50 30
Fort Lauderdale 88 75 87 76 / 30 20 50 40
Miami 90 75 89 76 / 40 20 50 40
Naples 89 75 85 75 / 40 30 50 30