Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Miami Florida
738 am EDT Sat Aug 23 2014
high pressure will remain over the eastern Gulf of Mexico today
while a tropical disturbance moves west northwest into the
southern Bahama Islands from Hispaniola. This will allow for a
northeast wind flow over most of the taf sites today...except for
kapf taf site where it will be from the westerly direction due to
the West Coast sea breeze. The wind speeds will be light until
around 15z then increase to 5 to 10 knots.
There should not be as much coverage of thunderstorms today over
South Florida due to the drier air working into the area from the
northeast. However...the taf sites over South Florida could still
see some showers today. So have added vcsh to all of the taf sites
from around 15z until 00z today. The ceiling and visible should also
remain mostly in the VFR conditions today...except when a shower
moves through which could reduce the visible and ceiling down into the
MVFR conditions. However...the timing of the reduce visible and
ceiling should be less than 30 minutes when it does occur.
Previous discussion... /issued 255 am EDT Sat Aug 23 2014/
Short term (today-monday)...
deep easterly flow will dominate across South Florida today as a middle
level ridge is centered over the lower Mississippi Valley and a
surface ridge is located over central Florida into the Atlantic.
Drier air aloft will also move across the region today and Sunday
with precipitable water at around 1.5 inches or even slightly below which is well
under the average for late August. So chances for
shower/thunderstorm activity will be down considerably this weekend
with the main threat being over the interior and the southwest
Some uncertainty will begin to take shape on Monday as the ridge
centered along the central Gulf Coast builds north as a trough moves
into the North Atlantic. The tropical disturbance currently located
along the north coast of Hispaniola is forecast to move into the
central Bahamas late Sunday or Monday. The 18z run of the GFS gave
South Florida a little bit of a scare but the 00z run has now
shifted back to the east. The European model (ecmwf) is farther to the east with its
development and has also been more consistent with this track
guidance. The European model (ecmwf) also shows the trough moving into the Atlantic
stronger and deeper with a substantial moisture increase across
South Florida with precipitable water increasing back to over two inches. Both
models indicate a northeast steering flow developing and this would
still gear storm coverage towards the interior and southwest
Long term (tuesday-friday)...
the first part of the extended period remain uncertain at this time
as to the tropical development. If the system does indeed develop,
it will all depend on the strength of the northern trough axis
and the ridge over the southeast states. Most model guidance is
keeping the system to the east of the Florida Peninsula, but if
the ridge builds strong enough and the trough is not quite as deep
as currently being forecast then a westward shift is not out of
the realm of possibility. In other words, continue to monitor
forecasts from NHC. In the latter half of the extended period into
the end of the week, a deep layer ridge is forecast to return to
South Florida with abundant tropical moisture and precipitable water returning
to near 2 inches.
an easterly wind is forecast to continue through much of the
period at 15kt or less. However, much depends on possible tropical
development north of Hispaniola spreading into the central Bahamas
this weekend. Early next week, computer model spread is quite
large due to the uncertainty of steering flow over the Atlantic.
Mariners should keep a close look at forecasts from NHC through
the middle of next week.
Preliminary point temps/pops...
West Palm Beach 91 80 92 80 / 20 0 10 10
Fort Lauderdale 92 80 92 80 / 20 0 10 10
Miami 93 80 94 80 / 20 0 10 10
Naples 92 77 94 79 / 20 10 30 30