Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Miami Florida
744 am EDT Tuesday Oct 13 2015
Mainly VFR conditions expected through the forecast period.
Regional winds are currently light and variable. West and East
Coast sea breezes are expected to form in the 16-18z time frame.
Around 00z likely to become light and variable again.
Previous discussion... /issued 355 am EDT Tuesday Oct 13 2015/
Short term (today-wednesday)...
current upper air analysis shows South Florida sitting beneath the
base of a large trough centered over the Great Lakes with a weak
surface ridge stretching from the eastern Gulf of Mexico across
South Florida and into the western Atlantic. This is maintaining a
deep west to northwest flow across the region with decent amounts of
low level moisture remaining over the area with precipitable water from last
evening's 00z mfl sounding at 1.52". Forecast soundings show a
similar pattern throughout the day today except for a more southerly
flow at the very low levels and a slight nudge up of low level
moisture with precipitable water increasing to around 1.6-1.7" by this afternoon.
So with the light wind field, a sea breeze is likely to develop
along the East Coast and the slight moisture increase could be
enough to set off a couple of showers and some high resolution short
term model output suggests this. The hrrr was more aggressive in
earlier runs but has since backed off on much development so will
lean towards the mav guidance and just go with a slight chance of a
shower along the southeast coast. The NAM maintains the low level
inversion so thunder will remain none.
All of the global models and the high resolution short term models
show a return of moisture on Wednesday as an east to southeast low
level flow slowly begins to emerge as the surface ridge nudges
northward and the precipitable water increases to near 2". The NAM also shows the
cap eroding by Wednesday afternoon. So probability of precipitation will be on the increase
at least across the southern areas along with a slight chance of
thunder by the afternoon. Not much change is foreseen on Thursday
except for the easterly flow deepening supporting an increase in
rain chances. However, I can also see this forecast trending down as
time GOES on as these patterns are never handled very well by the
models and sometimes are way too aggressive in the moisture
Long term (thursday-monday)...
only some subtle changes are seen in the extended period as a large
scale middle level cyclonic flow will remain over the eastern states. A
large surface high pressure ridge will move out of Canada into the
northern plains on Friday night and move to the Middle Atlantic States
by Monday. This will keep the deep layer moisture over South Florida
from moving very far to the north and in fact some models suggest it
could be shoved back to the south over the weekend. At the same
time, the surface ridge along the Middle Atlantic States is forecast to
be 1035mb which will cause a strong pressure gradient to develop
across the Florida Peninsula leading to an increased threat for
rip currents at the Atlantic beaches over the upcoming weekend.
good boating conditions will exist through the early this weekend
as wind remains below 15 knots. High pressure currently exists
across the South Florida waters and the ridge will slowly shift
north through the week.
Preliminary point temps/pops...
West Palm Beach 86 73 88 74 / 10 10 30 20
Fort Lauderdale 87 76 88 76 / 20 30 40 30
Miami 88 75 88 77 / 20 30 40 30
Naples 87 73 87 74 / 10 10 30 10