Scientific Forecaster Discussion
fxus62 kmfl 181201
Area forecast discussion
National Weather Service Miami Florida
801 am EDT Wed Sep 18 2019
Primarily VFR cond. For all sites throughout the period. Storm
activity should diminish over Atlantic waters throughout next
couple hours. Convective coverage this afternoon should be minimal
and generally focused over the interior and Gulf Coast. Left
rain showers/thunderstorms and rain out of tafs for now but may be needed later, especially
for kapf. Gusty north-northeast winds today should remain strong through this
Previous discussion... /issued 300 am EDT Wed Sep 18 2019/
Today through Thursday night...
A low amplitude wave--now evident in moisture channel imagery across
central Florida--will continue its trek equatorward through the
morning hours. This should bring a slight uptick in shower chances
early this morning, primary for the Atlantic waters and East
Coast Metro areas. Thereafter, the strong pressure gradient
between Hurricane Humberto and surface ridging over the eastern
Gulf of Mexico will bring breezy northeasterly winds with
afternoon/evening shower chances confined to interior southwest
Florida and the Gulf Coast. Given the seasonally low precipitable
water values and relatively shallow moisture depth rain coverage
should remain in the slight chance to chance range, with most
areas remaining dry. The onshore wind component should bring
slight cooling to the East Coast Metro areas, where highs should
remain in the upper 80s. Inland values should top out in the lower
90s. Given the drier air in place, overnight lows for interior
areas should drop into the lower to mid 70s, with upper 70s to
around 80 common along the coasts.
The synoptic pattern should remain somewhat similar on Thursday,
with ridging holding court across the Gulf of Mexico and residual
troughing from Humberto located to our east. This will maintain and
even strengthen the pressure gradient resulting in gusty conditions.
The mean 1000-850 mb wind magnitudes peak out at around 30 kt by
Thursday evening/night with downward momentum transport--in the form
of wind gusts--into the surface layer likely maximized during this
time. This evening surge of wind will be accompanied by some
moisture and increased differential cyclonic vorticity advection
thus shower chances should increase for the Atlantic waters and
East Coast Metro areas from late Thursday afternoon into Thursday
night. Temperatures should be similar to on Wednesday, but perhaps
a touch cooler for eastern areas given strong onshore flow.
Friday through Sunday...
High pressure becomes established from the Gulf of Mexico through the
western North Atlantic (south of the departing humberto) allowing an
easterly wind regime to become established across our area. This
will bring a surge of low to mid-level moisture into our area in
association with a low pressure trough during this period. Expect an
uptick in shower and thunderstorm coverage, with an enhancement to
the daily diurnal cycle likely at a minimum. There are some
suggestions that drier air may begin working into our area towards
the end of the weekend, but not enough confidence in this solution
just yet with the low-level trough remaining nearby. As such,
deferred to a consensus model blend for pops during this period.
Monday and Tuesday...
The low pressure trough should meander near/just south of our area
as what is now tropical depression 10 gains latitude well to our
east. Due to low predictability in the exact placement of these
features this far out rain coverage is somewhat uncertain. Will
defer to blended pops for now until the synoptic pattern is better
elucidated going forward.
Substantial swell from Hurricane Humberto combined with fresh to
strong north-NE breezes will produce rough seas across the Atlantic
waters, especially over the Gulf Stream where wave heights may
exceed 10 feet through late week. A Small Craft Advisory remains in
effect for the Atlantic waters through this weekend. Small craft
should exercise extreme caution, especially around jetties and
A high risk for rip currents will continue this week for the
Atlantic beaches due to strong onshore winds and substantial swell
from Hurricane Humberto. High surf is also anticipated, particularly
for Palm Beach County where localized beach erosion is possible due
to surf heights in the 7 to 10 ft range. Swimmers and beachgoers are
urged to use extreme caution this week and follow the instructions
of lifeguards and other public safety officials.
Preliminary point temps/pops...
West Palm Beach 87 78 85 77 / 20 30 50 40
Fort Lauderdale 87 79 85 78 / 20 20 40 40
Miami 88 78 86 77 / 10 20 40 40
Naples 90 76 88 73 / 30 0 20 10
Florida...high rip current risk through Sunday evening for flz168-172-173.
High surf advisory until 8 PM EDT Sunday for flz168.
Am...Small Craft Advisory until 8 PM EDT Sunday for amz630-650-651-