Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Miami Florida
1036 am EDT Sat Aug 30 2014
Sal characteristics in the lowest levels of the sounding this
morning evident with some hazy skies also observed today. Lapse
rates and 500 mb temperature are very favorable for storms, however 12z mfl
precipitable water was 1.49". Considering the lapse rates and 500 mb temperatures were
similar yesterday and activity was scattered at best along the
East Coast, expecting the same or less today through the cities.
Models aggressive with storms firing this afternoon near Naples
and much of western Collier and Hendry counties, customary with
deep easterly flow. Based on the height of the freezing level and
lapse rates, there is a chance of a few strong storms with hail
this afternoon interior and West Coast. Only change to current
forecast was to increase probability of precipitation Naples/western Hendry/western
Previous discussion... /issued 801 am EDT Sat Aug 30 2014/
For the East Coast terminals...there is an area of
showers/thunderstorms in the northwest Bahamas with deep moisture
and some showers extending westward towards South Florida.
Terminal kpbi could experience light to moderate showers this
morning although mainly VFR conditions expected to prevail. With
the influx of deep moisture...thunderstorms in the vicinity assigned to all East Coast
terminals at 16z. With any shower/thunderstorm activity very brief
IFR conditions may be possible.
For terminal kapf...with high pressure prevailing across the
region and resultant moderate easterly winds...the West Coast sea
breeze may not develop with the kapf taf wind forecast indicating
southeasterly winds in afternoon. As the afternoon progresses
shower/thunderstorm activity is expected to increase across the
western peninsula with thunderstorms in the vicinity assigned at 18z.
Previous discussion... /issued 349 am EDT Sat Aug 30 2014/
* maximum heat indices hitting 102-108 today
* moderate risk of rip currents Atlantic beaches
* strong tstorm potential western interior/Gulf Coast this
heat indices are still in the 90s at this early morning hour
across the East Coast metropolitan areas where it has not rained.
A Saharan air layer is over South Florida and will remain overhead
today. Lidar and sounding data show that this sal is rather
low...maxed at 1 km. Forecast soundings show this layer with a cap
and steep lapse rates/dry air above it. However, this is not a
strong sal so it won't limit convection as would a strong episode.
As such, moisture will be sufficient and with the presence of the
sal (steeper lapse rates above an inversion) and 500 mb temperatures cooling
to near -8c...we could again have strong thunderstorms this
afternoon across the western interior/Gulf Coast region where
convergence will be best...though not optimal. That's one negating
factor for robust convection...the low level wind flow will be
easterly at near 15 knots which likely will prevent a full blown Gulf
sea breeze from developing. However, there still will be some
convergence with wind flow veering along the Gulf Coast. Will
Orient probability of precipitation from isolated East Coast to scattered category Gulf
Coast...where frequent lightning/strong wind gusts will be
Maximum heat indices are forecast to be in the 102-108f range across
South Florida today...due to lower to middle 90s maximum temperatures and
dewpoints well into the 70s.
Onshore winds will result in a moderate risk of rip currents along
the Atlantic beaches today.
The sal will depart the area on Sunday as ridging across North
Florida moves this area westward on the easterly wind flow. A deep
layered ridge will remain over North Florida with deep easterly
flow across South Florida next week. A TUTT/upper level trough
east of the Bahamas will continue to move westward. Model
consensus takes this to the Bahamas during the middle part of next
week while opening up. GFS/European model (ecmwf) show a low level trough moving northwest
and across the area middle week....leading to an increasing chance of
showers and thunderstorms then. Guidance indicates increasing probability of precipitation
beginning tomorrow as well. No significant weather features...but
it looks unstable and sufficiently moist and as such followed the
pop trends in the guidance through next week. /Gregoria
Marine...a light to moderate east to southeast wind will prevail
across the local waters as the Atlantic ridge remains across North
Florida. Seas will prevail less than 4 feet through next week.
Winds/seas will be higher in and near an increasing chance of
thunderstorms early next week.
isolated showers will continue to develop and move northwest over
the Atlantic waters early this morning...before drier air works
into the area from the Bahama Islands. A few of the showers could
even work into the East Coast taf sites. Therefore...a vcsh will
be put in for the East Coast taf sites through 14z today before
going dry for rest of today.
The winds over the East Coast taf sites will remain east to
southeast at 5 to 10 knots increasing to around 12 knots after
14z. The winds at kapf taf site will be easterly at 5 to 10 knots
through most of today...but could become more southerly late this
afternoon after 20z when the West Coast sea breeze tries to
develop. So will also put in thunderstorms in the vicinity for kapf taf sites between 21z
and 00z today.
The ceiling and visible will also remain in the VFR conditions today
at all of the taf sites. /Bnb
Preliminary point temps/pops...
West Palm Beach 92 79 90 79 / 30 20 30 10
Fort Lauderdale 92 81 91 80 / 20 20 20 10
Miami 92 80 90 80 / 20 20 20 10
Naples 91 77 92 77 / 60 20 60 20