Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Melbourne Florida
943 am EDT Tuesday Sep 30 2014
..Flood Watch continues in effect into this evening...
..Locally heavy rain likely with showers and storms again today...
Current-this afternoon...radars detecting showers moving west to
east in the eastern Gulf of Mexico coming ashore between Tampa and
Cedar Key. Water vapor satellite imagery showing drier middle and upper
level air mass reaching south to roughly a Cape Canaveral to
Sarasota line. The 30/12z soundings from Tallahassee and
Jacksonville show a much drier air mass above 500mb...Tampa heading
that way while Miami was still very wet through the column. Closed
1007mb low analyzed east of Jacksonville. Associated front...based
on buoy observation/twc analysis...just north of east central Florida.
Whatever northwest tilt to the middle level/500mb flow there was
earlier flattens during the day per latest RUC/GFS runs.
The southward progress of the front may slow down as the flow aloft
flattens. Main problem looks to be training showers/storms south of
the front over already very soggy/saturated land.
Current 70 north 60 south pop looks good given the very wet air mass
ahead of the front and middle level impulses moving west to east over
central Florida during the day. Like Monday...late afternoon early
evening storms for the east side of the peninsula a good bet.
Previous zones discussion
Today...a slow moving front will move southeast toward lake and
Volusia counties into middle day and through the Orlando metropolitan and
northern Brevard County into the late afternoon and toward southern Brevard
County and Osceola County toward early evening. The frontal boundary
will provide a focus for showers and storms with locally heavy rain
again today...mainly during the afternoon and early evening hours.
Deep moisture will continue across east central Florida with precipitable
water values around two inches. Weaker impulses are prognosticated in the
middle level westerly flow but should still be sufficient to aid in
convective development espec near the approaching low level frontal
boundary across the northern half of the forecast area. One concern for
today is that showers and storms may train from west to east with
the middle layer flow almost parallel to the approaching front sliding
south. Another concern is that the areas that will likely
see the heaviest rainfall today are those same areas that have seen
abundant rainfall over the past week or so...generally from Osceola
and Brevard County northward to lake/Volusia counties including the
Orlando metropolitan. Have raised probability of precipitation to 70 percent from Osceola and Brevard
northward and will keep 60 percent across the far south. Highs will be
in the middle-upper 80s north and upper 80s to near 90 around Lake
Tonight...will indicate highest evening probability of precipitation from Lake County into
the Orlando area and southeast into Brevard where the low level frontal
boundary should provide a focus for showers and a few storms into
the evening hours. After midnight will keep a slight shower chance
over land but most of the rainfall should have ended. Lows in the
Wed-Thu...the previous weak frontal boundary will slide slowly south
of central Florida on Wednesday but will be close enough in proximity
along with ample deep layer moisture to spark at least a 50 percent
chance of afternoon convection across east central Florida. Moisture
remains abundant into Thursday and with periodic middle-level impulses
embedded in the near zonal flow aloft should still warrant chance
wording for afternoon showers/storms especially southward. The
pressure gradient will be fairly weak both days with the East Coast
sea breeze providing an additional focus for storm development.
Steering flow for cells remains from the west to the east so any
activity over the interior during the afternoon/early evening could
work back towards the East Coast late in the day. Locally heavy
rainfall will be possible with nuisance flooding possible across
areas that have seen recent heavy rainfall totals.
Fri-Mon...upper troughiness across the eastern Continental U.S. Will help push
another front into North Florida late on Friday and then through
central Florida on Sat. By sun this boundary will lie across South
Florida and the Florida Straits. Moisture will again pool along and
ahead of this boundary. An East Coast sea breeze boundary will
develop and move slightly inland again on Friday but the deep-layer
westerly flow on Sat will likely inhibit development. Model guidance
suggests between a 40 and 50 percent chance of convection for each
of these days ahead of the front with drier conditions for both
sun/Mon. Any precipitation late in the weekend (sun) or for the
start of next week (mon) will be confined along the Treasure Coast
and southward...mainly in the afternoon where residual moisture may
MVFR tempo IFR kism-kmlb north. VFR tempo MVFR/IFR south of
kism-kmlb this morning as stratus moves through. Prevailing MVFR
this afternoon tempo IFR in/near rain showers/thunderstorms and rain through sunset.
Previous aviation discussion
early morning stratus will affect northern terminals through around 12z
with some IFR ceilings. Frontal boundary moving southeast toward northern terminals by
middle day into the afternoon will bring with it rain showers/thunderstorms and rain chances and
SW/west winds becoming northwest/north behind the boundary and NE late for
kdab/klee. Will indicate highest rain chances from 16z-23z with
tempo rain showers for most terminals.
current-this afternoon...nearshore buoys recording southwest to west
winds 10 to 15 knots. The buoy 120nm east of New Smyrna Beach was
record southwest around 15 knots. All the buoys were recording 2 to
3 foot seas.
Southwest to west winds 10 to 15 knots nearshore and around 15 knots
well offshore ahead of a slow moving front this afternoon. Seas
remain 2 to 3 feet.
No significant changes for the marine forecast update.
Previous marine discussion
offshore winds will become northerly across the northern waters tonight
but not to strong up to around 10 knots. Seas 2-3 feet near shore and
3-4 feet well offshore.
Wed-Sat...the frontal boundary will slowly move south of the coastal
waters on Wednesday with a daily sea breeze expected each day through Friday.
Another front will drop into the area on Sat. Light offshore winds
will likely develop each night with the weak pressure gradient in
place and onshore flow developing each afternoon through Friday from sea
breeze formation. Wind speeds at or below 15 kts. Deeper westerly flow on
Sat likely to inhibit sea breeze development on this day. Westerly
steering flow for storms over land will continue through the period
with the realistic threat for afternoon/evening storms to move over
the intracoastal and near shore waters of the western Atlantic.
Ample moisture continues over the area with a 40 to 50 percent
chance of afternoon/evening storms. Seas 2-3 feet...except possibly
some 4 feet seas returning and well offshore on Sat. Primary threats
to small craft boating from storms remain cloud to water
lightning....gusty winds...torrential downpours and locally higher
St Johns River at Astor continues slightly above flood stage at
Astor with water levels also rising near Deland and Lake Harney...
may approach or reach action stage later this week. Shingle Creek
has also been on the rise to within a half foot of action stage at
Campbell this morning. Will continue to monitor with the possible
need for a short fuse flood statement or warning in this area late
today should heavy rain develop over the Shingle Creek basin.
Preliminary point temps/pops...
dab 85 72 86 74 / 70 40 50 30
mco 87 72 89 73 / 70 50 50 30
mlb 87 73 87 74 / 70 50 50 30
vrb 88 72 88 74 / 70 30 50 30
Lee 87 73 89 74 / 70 40 50 30
sfb 87 73 89 74 / 70 50 50 30
orl 87 74 89 75 / 70 50 50 30
fpr 88 72 88 73 / 70 30 50 30
Florida...Flood Watch through this evening for coastal Volusia-Indian
River-inland Volusia-Martin-northern Brevard-Northern Lake-
Southern Lake-St. Lucie.