Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Miami Florida
231 PM EDT Wednesday Apr 16 2014

Short term (tonight-Friday night)...
the short term could be an active weather pattern for South Florida.
The weak cold front that moved through the area last evening has now
stalled over the Florida Straits as the upper flow pattern becomes
more zonal with the middle/upper level trough lifting rapidly to the
northeast. Another middle level trough will begin to move out of the
southern rockies into the Southern Plains late tonight and Thursday.
This will allow for the low level flow to become east to southeast
and the frontal boundary will begin to lift back north late tonight
to near Lake Okeechobee by late Thursday afternoon. As the middle
latitudes remain very progressive along with the deepening trough
over the southern U.S., This will keep 500mb temperatures in the
-11 to -12c range across South Florida along with in the warm
sector south of the boundary for daytime Thursday. This will
steepen lapse rates considerably for Thursday and will be
increasing the threat for thunder. Forecast soundings also show
precipitable water increasing to around 1.5 inches which is considerably above
the average for middle April. Due to the general east to southeast
low level wind flow expected, the eastern coastal region will have
a negligible convergent zone so the primary risk will be interior
and the Naples area especially if a West Coast sea breeze can
materialize.

There continues to be some uncertainty looking ahead into the end of
the week. The middle level trough will continue to deepen as it moves
into the southeast Gulf Coast states on Friday and surface
pressures lower in the northeast Gulf of Mexico as a result. The
concern is the difference in the model runs as to the intensity
of the entire system. The European model (ecmwf) has been very consistent over the
past many runs showing a closed middle level circulation in the
eastern Gulf by Friday with a deep southerly flow of tropical air
into South Florida through Friday night. The NAM began showing
this same solution on its 06z-12z runs although it shows the
deepest plume of moisture to our north. The GFS has been reluctant
to show such an intense system but the 12z run comes closer to
this solution, albeit faster and weaker. It now shows the low
cutting off late Friday night over northeast Florida which would
push most of the active weather east of the peninsula while the
European model (ecmwf) has a much slower evolution due to its cutting the low off
much earlier and farther to the west. Therefore, it keeps active
weather through all of Friday night. At any rate, it looks as
though there will be at least a chance of thunderstorms both
Thursday and Friday with a slight risk of strong to possibly
severe. The exact timing of any such storms on Friday and Friday
along with their intensity will come with later updates as the
models come to terms with their solutions.

Long term (saturday-wednesday)...
the extended period also remains in limbo due to how fast the upper
system evolves across the southeast. The GFS still wants to bring
in drier and more stable air by late Saturday through the rest of
the weekend and into next week. The European model (ecmwf) delays the drying and
stabilizing until late in the weekend. So again will need to
watch this over the next few forecast cycles before a consensus
is made.

&&

Aviation...
broken VFR ceilings expected this afternoon and evening...with possible MVFR at
times. As moisture increases overnight...increasingly likely that 2-
3kft stratus will prevail...so have introduced MVFR conditions after
6z. Shower chances are still uncertain...but at least scattered
activity warrants vcsh after midnight.

Winds will be north-northeast today...become east-northeast overnight. Speeds will
generally be around 10 knots.

&&

Marine...
the wind direction over the South Florida local waters
has become easterly and will remain so through Thursday before
continuing to swing to a southerly direction on Friday. The wind
speeds over the South Florida local waters will be 15 knots or
less today into Friday.

There could be some small northeast swells over the Palm Beach
waters late tonight into Thursday before subsiding by Thursday
night. So the seas in the Palm Beach waters should build to 7
feet late tonight into Thursday...before subsiding below 7 feet
Thursday night into Friday. Rest of the Atlantic seas will remain
below 7 feet along with the Gulf seas.

&&

Preliminary point temps/pops...
West Palm Beach 73 82 73 82 / 20 60 40 60
Fort Lauderdale 74 83 74 83 / 30 50 30 50
Miami 74 83 74 83 / 30 50 30 50
Naples 69 84 69 82 / 20 50 40 60

&&

Mfl watches/warnings/advisories...
Florida...none.
Am...none.
GM...none.
&&

$$

Short term...23/sk
long term....30/kob
aviation...23/sk