Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Melbourne Florida
940 am EDT Thursday Jul 30 2015
Low east of Georgia/South Carolina will continue to track away from
the East Coast. Upper level/500mb troughing between upper
level/500mb highs over Southern Plains to the west and east of the
Bahama Islands east in the western Atlantic.
Latest rap forecast run shows the surface low continuing to track
slowly east northeast the next 12 hours. This track will maintain
the offshore flow. Local WRF models suggesting a sea breeze
developing from Cape Canaveral north where the offshore winds are
forecast to be lighter. Potential for some stronger storms over the
north forecast area where slightly cooler upper level temperatures
reside and at the coast where there maybe sea breeze interacting
with the prevailing westerly flow.
Changes to mainly the various wind grids.
Prevailing VFR through 18z. Tempo MVFR thunderstorms in the vicinity 19z-21z. VFR 31/00z
through 31/08z. Tempo IFR/MVFR ceilings/visibility 31/08z-31/14z due
to low clouds/mist/fog.
Buoy 009 was recording southwest winds around 10 knots and 2 foot
seas. The two scripps buoys at 4nm and 6nm off the beach were
recording 1 foot seas.
Afternoon sea breeze Cape Canaveral north...offshore winds south of
Cape Canaveral and remainder of coastal waters.
Today-tonight...models show that the area of lower precipitable
water values...that slipped into northern areas yesterday...
moistening back up above 2 inches. This seems reasonable as the
peripheral drying from low pressure system offshore North Florida
lifts farther away to the northeast.
Had been a bit dubious about the 50-70 probability of precipitation advertised by MOS
especially since there was considerable debris cloudiness
overspreading the peninsula from convection offshore. Recent
trends show the clouds diminishing...and as the low pulls slowly
northeast...expect this trend to continue. Therefore most places
should heat up to around 90 or the lower 90s. The models have been
showing temperatures aloft cooling to around minus 7 celsius. Therefore
expect a few more strong storms...with frequent lightning strikes
being the main danger. Forecast soundings show some lingering
drier air aloft...so isolated strong wind gusts 50-60 miles per hour could
As far as distribution/timing of the storms...would expect a
general scenario similar to yesterday with showers/storms moving
across southern sections earliest (where the strongest/deepest
westerly flow will exist). The local WRF and hrrr models generally
show this occurring...with later and slower moving storms expected
across the north as boundaries interact. These storms could be
the strongest of the day.
MOS has probability of precipitation 50-60 percent in the south tonight...but given the
above discussion...have trended below those unable-climatological
Friday-Friday night...weak area of low pressure at 500 mb lingers off of
the immediate east Florida coast with middle-level high pressure
ridging extending north of the area across the Gulf Coast states.
At the surface high pressure ridging remains suppressed across the
southern Florida Peninsula/Florida Straits. A weak area of surface low
pressure off of the Carolinas early in the period will lift fairly
rapidly northeastward away from the area. Deep layer moisture
continues with precipitable water values in excess of 2 inches
across much of the area. Subtle impulses aloft...deep moisture and
boundary interactions through the day will allow for high end chance
probability of precipitation (50 percent) near I-4 corridor northward (aftn/evening) and
likely chances (60-70 percent) southward. Schc/low end chance wording
for probability of precipitation during the morning. Lowering rain chances Friday night though
realistically there will remain at least a slight chance across ecfl
overnight. Storm movement mainly out of the SW or west. Highs in the
u80s to around 90 and lows generally in the M/u 70s.
Weekend...surface ridge axis will remain situated over the southern
Florida Peninsula as south-southwest/SW flow continues in the low-levels. Aloft...a
generally troughy pattern continues along the eastern Seaboard to
include the Florida Peninsula. We also maintain the deep moisture
and relatively warm temperatures aloft. The storm motion while weak
will generally favor a west to east movement. Locally heavy
rainfall...gusty winds and cloud to ground lightning will remain the
main convective threats. With this persistent pattern will keep
lower end schc/chance probability of precipitation during the morning and mainly likely (60
percent) mention for the afternoon/early evening periods. Highs/lows
will remain consistent from what we have been seeing recently.
Mon-Wed...aloft...as the high pressure ridging continues to amplify
over the western U.S. The general troughiness will continue across
the eastern Continental U.S.. the surface Atlantic ridge will begin building
back northward Tuesday-Wednesday as the eastern Continental U.S. Low-level troughing
shifts west over the Gulf of Mexico. Expect moisture to remain high
and probability of precipitation 50 percent or a little higher still seem warranted...except
possibly trending lower Wednesday...if the surface ridge does indeed build
back into central Florida.
Aviation...a few MVFR ceilings will occur until a little after
sunrise. There is a little more low level wind this morning...but
local IFR could briefly occur too. Then the main forecast problem
becomes the timing of storms. Expect that from about kvrb-ksua
there will be a chance for storms rather early again...about
16-20z...with the remaining terminals likely having the greatest
chance between 18-22z. A few strong storms with wind frequent
lightning strikes and gusty winds over 30 knots are expected again.
today-tonight...southwest wind flow regime will continue with
speeds 10-15 knots offshore and 5-10 knots close to the coast. The
main mariner concern will be offshore moving showers/storms which
could move offshore the Treasure Coast by early afternoon.
Steering flow will be weak northward to the Volusia coast...but a
few strong storms could affect the nearshore waters late in the
Friday-Friday night...surface ridge axis remains suppressed to the south.
Mainly south-southwest/SW winds around 10 kts. Seas generally at or below 3 feet.
Winds/seas locally higher in vicinity of of stronger convection. Offshore
moving storm cells remain a threat through the period. Coverage of
showers/storms looks rather high and storms should start to produce
more frequent lightning strikes.
Sat-Mon...surface ridge axis across the southern peninsula into
early next week. Little change in moist south-southwest/SW wind flow regime.
Storm motion still offshore but weaker. Boaters should continue to
be vigilant for marine storms... especially during the afternoon and
evening. Wind speeds at or below 15 kts with seas 2-4 feet generally.
Preliminary point temps/pops...
dab 90 74 90 74 / 60 30 50 30
mco 91 74 90 74 / 60 30 50 30
mlb 91 73 89 74 / 60 30 60 40
vrb 90 73 89 72 / 60 30 70 40
Lee 89 76 91 76 / 60 30 50 30
sfb 92 75 91 74 / 60 30 50 30
orl 91 76 90 75 / 60 30 50 30
fpr 90 73 89 73 / 60 30 70 40