Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Miami Florida
923 am EDT Sat may 23 2015

Update...
surface analysis from this morning showed a leftover boundary
along the East Coast of Florida this morning east northeast of
Lake Okeechobee. Showers and storms may focus near this boundary
late this morning into the early afternoon and then move to the
west and southwest towards the interior and Gulf Coast. The 12z
sounding showed drier low level air and warmer temperatures aloft
compared to yesterday. So the lower instability will lead to a
lower threat of strong storms compared to the past couple days.
However...an isolated strong storm or two cannot be ruled out
across the Gulf Coast this afternoon...with the main threats being
frequent lightning...gusty winds up to 50 miles per hour...small hail...and
heavy rain.

The flow has become east to northeast in the low/middle levels due
to high pressure building over the middle Atlantic and southeast
states. This flow will strengthen throughout the day and over the
Memorial Day weekend...with life threatening rip currents likely
at the East Coast beaches by this evening and continuing through
Tuesday. Isolated/scattered showers and a few embedded storms have
developed over the Atlantic waters and were moving towards the
East Coast metropolitan areas. A waterspout was also reported about 16
miles east of Miami Beach this morning. Waterspouts will remain
possible...especially this morning...over the Atlantic waters.
Bumped up probability of precipitation for the East Coast and added slight chance of
storms. Isolated/scattered showers and a few storms are possible
for the East Coast metropolitan areas...mainly through early afternoon.
Storms will then focus across the Gulf Coast this afternoon as the
East Coast sea breeze pushes inland and a weak Gulf Coast sea
breeze develops. The hrrr and local WRF models show the Lake
Shadow on the west and southwest sides of the Lake May inhibit
development...so lowered probability of precipitation there.

&&

Previous discussion... /issued 738 am EDT Sat may 23 2015/

Aviation...
light winds early this morning will become NE/east by 14z as high
pressure begins to establish itself across Florida. VFR conditions
will prevail despite hazy/smoky skies early this morning. Narrow
area of showers and possibly a thunderstorm may affect fll/pbi areas this
morning through about 18z with vcsh included at these terminals.
Easterly flow will shift showers/thunderstorms to the western half of the
peninsula after 18z with tempo thunderstorms and rain and MVFR at kapf. Most of the
showers/thunderstorms should wind down by or shortly after 00z with mostly
VFR conditions tonight. /Molleda

Previous discussion... /issued 342 am EDT Sat may 23 2015/

Discussion...

Weak surface trough, this very early morning, left over from weak
low pressure/stationary front over central Florida yesterday, will kick
off a few showers/storms offshore and near the beaches of Palm
Beach/Broward/Miami-Dade counties. As strong surface high
pressure moves off the East Coast today, the pressure gradient
increases into Sunday and the resulting deep easterlies lead to a
high risk of rip currents for the Holiday weekend. A pocket of
drier air aloft compared to yesterday, will be forced into the
East Coast on veering 850 mb and 700 mb wind flow later today. Precipitable waters may
drop off slightly by this evening. NE to east winds will combine with
a late day Gulf Breeze to place most showers/storms across the
West Coast and interior sections. Although 500 mb temperatures warm slightly
and 700 mb-500 mb lapse rates decrease a little compared to yesterday,
can't rule out a few stronger storms West Coast today.

Showers may form along the East Coast tonight and during part of
Sunday morning as the easterlies really get underway. Downright
breezy into Sun afternoon with some 25kt gusts along the East
Coast possible. Some of the morning coastal showers may penetrate
inland. Monday looks similar, but again most storms will be
interior and West Coast.

With the cold 500 mb trough lifting from the northeast Sunday, and a
deep West Coast/Four Corners trough persisting, a middle level ridge
will have free reign to grow and expand not only over Florida, but
eventually over the southeast Continental U.S. Coast. With the ridge cutting
off through h3, large subsidence will lead to a significant amount
of drier middle-level air across the East Coast and Florida by the
middle of next week. Model soundings actually drop precipitable waters close to 1"
at times along the East Coast. Although there will remain
opportunities for storms on the West Coast, probability of precipitation will be rather low
by midweek region-wide.

As the 500 mb ridge and surface high eventually move northeast and
away from the eastern Seaboard, the gradient will relax and
persistent moderate easterlies will begin to weaken a bit into
late week.

Marine...

The gradient increases as surface high pressure moves off the
eastern Seaboard today. Winds become increasingly easterly and
stronger through the weekend, close to 15kts by late today, then
near 20kts sustained late Sunday and Monday, else 15-20 kts through
the rest of the forecast. Middle and upper level high pressure will
remain anchored along the East Coast.

&&

Preliminary point temps/pops...
West Palm Beach 88 78 87 79 / 30 30 30 20
Fort Lauderdale 88 78 87 79 / 30 30 30 30
Miami 89 77 88 78 / 30 20 30 30
Naples 93 73 93 72 / 70 30 60 20

&&

Mfl watches/warnings/advisories...
Florida...high rip current risk from 8 PM EDT this evening through Tuesday
afternoon for flz168-172-173.

Am...none.
GM...none.
&&

$$

Short term...84/AK
long term....21/km

National Weather Service Glossary of Abbreviations