Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Miami Florida
748 am EDT Monday may 4 2015
gusty easterly flow will prevail at all sites through the next 24
hours with VFR conditions. Flow should easily counteract any Gulf
Breeze at kapf. A few showers will be possible across the East
Coast sites for the latter half of this taf cycle as a middle level
trough moves into the Florida Straits...therefore added vcsh
after 02z for the East Coast sites.
Previous discussion... /issued 428 am EDT Monday may 4 2015/
one more relatively dry and pleasant day in store until changes
unfold late tonight through the middle-week period as low pressure
develops over the Bahamas Tuesday and moves north over the western
Atlantic into late week.
Short term (today through wednesday)...
high pressure keeping deep moisture to our south today, but
barely, as the middle/upper low over the southeastern Gulf begins to
pull the moisture north late. A slowly moistening air mass over
the area will be enough for a 20% pop over eastern areas as
moderate/strong east winds continue area-wide. Showers and a few
thunderstorms will increase and spread north/west into the area
late tonight as precipitable water values increase from around an
inch to 1.5 inches by Tuesday morning. Correspondingly, the
threat of heavy rainfall will begin early Tuesday, with the
greatest threat still looking like Tuesday into early Wednesday as
the low pressure takes shape just to our east. As in previous
forecasts, the deepest moisture and most favorable set up for
heavy rainfall will be over the Atlantic and western Bahamas.
However, with the rapid moistening of the local air mass, speed
convergence of the low level winds and our area under almost
ideal upper level divergence pattern between jet maxes over North
Florida and the central Gulf of Mexico, copious rainfall amounts
a distinct possibility over parts of metropolitan Southeast Florida. Wpc
quantitative precipitation forecast probabilities show reasonable possibilities of 24-hour rain
totals exceeding 3 inches along the coast. Models diverge on the
low development by Wednesday, with the GFS closer to the east-
central Florida coast and the European model (ecmwf) weaker and farther offshore.
The general model trend has been for the low to be slightly west
and closer to the Florida coast on Wednesday, and this will begin
to lift the deeper moisture to the north. So Wednesday could be a
transition day with heavy rainfall still possible but shifting
north as the day progresses.
With the middle/upper level low pressure overhead Tuesday and
Wednesday, atmosphere will be unstable enough for thunderstorms/gusty
winds in addition to the heavy rain threat.
Over the western half of the area, including the Gulf Coast,
highest shower/thunderstorm chances will be during the day on Tuesday,
with rain chances tapering off on Wednesday as the low moves north
and slightly drier air moves into the area.
Long term (wednesday night through next weekend)...
a more typical diurnal rainfall pattern looks to return by
Thursday as the low meanders off the southeast United States. This
means mainly scattered afternoon/evening thunderstorms over the
peninsula as winds becoming light east/southeast.
Small Craft Advisory conditions will continue over the Gulf and
Atlantic waters through at least early afternoon and possibly into
early Tuesday as strong pressure gradient remains between the high
to the north and the developing low to our south/east. Slow
improvement in winds and seas are expected Wednesday as the low
moves to the north, but this could change if the low becomes
stronger than expected, which is not likely but also not out of
the question. Locally rough seas will continue over all waters
through Tuesday, along with the high risk of rip currents at the
Preliminary point temps/pops...
West Palm Beach 82 72 77 69 / 20 40 70 50
Fort Lauderdale 82 72 78 70 / 20 40 70 60
Miami 82 72 79 70 / 20 50 70 50
Naples 86 69 83 69 / 10 20 50 20
Florida...high rip current risk through this evening for flz168-172-173.
Am...Small Craft Advisory for hazardous seas until 8 PM EDT this
evening for amz650-651-670-671.
GM...Small Craft Advisory for winds until 2 PM EDT this afternoon for