Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Melbourne Florida
11 am EDT Thursday Sep 18 2014
Patchy low clouds lingering from Vero Beach and Fort Pierce west to
the Kissimmee river will lift by noon. Morning cape sounding shows
much drier air above 850 mb but sufficient low level moisture
remains so expect scattered cumulus to develop. Have adjusted probability of precipitation just a
little...reducing rain chances along the Treasure Coast to 20
percent in order to show that the best chance for showers this afternoon
will be over the interior and around Lake Okeechobee. Light north/northwest
winds this morning will turn NE to east this afternoon. Our local
WRF and the hrrr model are in good agreement regarding expected
evolution of convection this afternoon showing the best chance for
showers and a few storms around Lake Okeechobee as well as the north
interior. Motion generally toward the S/SW.
Previous day 1 discussion...
little in the way of organized precipitation today as the relatively stable
airmass overhead limits vertical motion...while dry air aloft limits
potential for cumulus development. Broad low pressure over the west Atlantic will lift
NE...allowing hi pressure to build down the eastern Seaboard in its wake. As
it does...light nwrly winds through the h100-850 mb layer will veer to the
NE by midday...then to the east through sunset.
Northwest/NE flow regimes typically do not produce much in the way of
thunder over central Florida. Cannot completely rule out precipitation with surface
dewpoints in the l70s and h100-h70 mean relative humidity values ruining between
70-80pct. However...the dlvpg onshore flow will limit the window of
opportunity for coastal thunderstorms and rain development. Interior will have a better
opportunity as near full sun will allow temperatures to reach their
convective triggers by early afternoon. However...with precipitable water values
expected to drop to around 1... will be at or below 20pct over most
of the area....with go with 30 probability of precipitation around Lake Okeechobee due to
slightly higher moisture profile. Precipitation should burn out by sunset
or shortly thereafter.
Developing onshore flow will keep maximum temperatures along the coast in the
M/u80s...interior warming into the l90s. Min temperatures holding in the
l/m70s areawide overnight as the continuing onshore flow will
quickly modify whatever low dewpoint air that manages to filter into
the County Warning Area.
lingering MVFR ceilings at vrb/fpr will lift by 16z. Brief MVFR ceilings
will be possible elsewhere as surface heating works on low level
moisture but entrainment of drier air aloft should limit duration of
MVFR conds. Isolated rain showers/thunderstorms and rain after 17z pushing southward may impact
sfb/mco/Lee. Light north/northwest flow turning NE to east.
no significant changes to current coastal waters forecast.
Weak hi pressure over New England and the Middle Atlantic States will nudge its
way off the eastern Seaboard... allowing surface/boundary layer winds over the
local Atlantic to veer to the north/NE by midday...then to the east by late
afternoon...steady speeds between 8-10kts. Long period swells from Hurricane
Edouard will dampen over the local Atlantic through the day...subsiding to
2-3ft nearshore and 3-4ft offshore today...then 2-3ft areawide
tonight. Isolated rain showers limited to the Gulf Stream.
Preliminary point temps/pops...
dab 87 74 83 71 / 20 10 60 40
mco 91 73 87 69 / 20 20 60 50
mlb 87 75 84 73 / 20 10 70 50
vrb 86 73 85 73 / 20 10 70 50
Lee 91 74 88 68 / 20 20 60 40
sfb 91 74 86 70 / 20 20 60 40
orl 91 74 86 69 / 20 20 60 50
fpr 87 73 86 73 / 30 10 70 50