Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Melbourne Florida
335 am EST Wednesday Dec 11 2013
surface hi pressure extending from the middle Atlantic to the Red River valley is
providing the sole impulse to a weak cold front pushing through the
Central Peninsula this morning...early morning surface observation indicate the
frontal boundary in the vicinity of Fort Pierce-Punta Gorda...confirmed by
a band of high h100-850 mb relative humidity just S of the I-4 corridor. Surface/low level
winds already shifting to the NE behind the front in response to the
ridge building over the deep south. Surface dewpoints drop from the
M/u60s ahead of the front...to the l/m50s behind it. Little in the
way of rain outside of a pencil thin band of convection off the
an Arctic high pressure ridge building out of the northern plains will draw
the Post frontal ridge into its grasp and merge with it over the
Midwest. As this happens...the cold front will stall as it loses its
only source of forward momentum. However...despite the nearly
saturated h100-850 mb layer...the airmass overhead is almost completely
lacking in any middle/upper level dynamic or thermodynamic support. RUC
analysis shows no sig middle level vorticity/upper level divergence to speak
of...while lapse rates through the 850 mb-h50 layer are largely at or below 5.5c/km.
Local profilers indicate strong nearly winds just off the deck across
central/North Florida...but these will diminish by midday as the two
ridges undergo their merger. Wrly winds above 850 mb have already
diminished below 15kts across the Central Peninsula and will not be able
to produce much in the way of middle level evacuation. Any low topped
rain showers that manage to develop in the onshore flow will not have much to
sustain them once they move onshore. Will go with slight chance probability of precipitation
areawide...but impact from any precipitation will be quite low.
Onshore flow will strengthen overnight as the newly merged Post
frontal ridge drops into the deep south and tightens the local pgrad.
While this should keep the low level airmass sufficiently mixed to
prevent widespread fog from forming...there will be a period in the
predawn hours where surface/boundary layer winds will be light enough for
patchy fog to form.
Weak cool air advection associated with the NE low level winds will knock
a few degrees off maximum temperatures today...still 4-8f above average with afternoon
readings in the M/u70s...except l80s around the Lake Okeechobee
region. Low clouds overnight and NE flow will combine to keep min
temperatures in the l/m60s...10-12f above average.
Thursday...surface high pressure pushing toward the Tennessee Valley and southeast
states will increase the north-northeast low level flow and push a band of low
clouds through the area into the afternoon with some clearing across
northern sections in the late afternoon. Breezy northerly winds are
expected with windy conditions developing at the beaches. Isolated
showers will move south-southwest and onshore...with slightly higher shower
chances along coastal sections up to 30 percent. High temperatures
will be cooler and range from around 70 at Daytona Beach to the middle
70s for Orlando and upper 70s across the southern counties.
Friday...the surface high center near the NC coast will push offshore
with winds becoming easterly. Considerable low to middle level cloudiness
should push onshore from the Atlantic with isolated showers moving
onshore from around Vero Beach south to Martin County. Highs will be
in the 70s.
Saturday...a progressive pattern and middle level shortwave trough
approaching the southeast will allow a surface low pressure area to move
from MS across Alabama toward north Georgia into Sat evening. Low level flow will veer
to southerly on Sat with high temperatures warming into the lower to middle 80s.
A few showers may develop in the late afternoon but will keep probability of precipitation
below 15 percent for now. Sat night... the approach of the middle level
shortwave and surface cold front moving through the eastern Florida Big Bend
late will allow for S chance/chance of showers in the prefrontal
Sunday-Sunday night...the next cold front will move into east central
Florida Sunday or Sunday night with the 00z European model (ecmwf) slightly slower than
the GFS. Mostly cloudy skies expected with the front and the chance
for showers in the 30-40 percent range. Highs Sunday expected to again
be warm ahead of the front between 80-85 degrees. Lows in the upper 50s
north to middle 60s south.
Mon-Wed...surface high pressure across the southeast states will be reinforced
into middle week keeping north-north-northeast low level flow across the area. 00z ecm
was slower to move front through the area so have nudged GFS probability of precipitation up
a bit and gone 30 percent all areas Monday. By Tuesday into Wednesday...the front
should push south of the state with a drier Continental airmass
taking hold with more sunshine and seasonable temperatures which
should run above normal...in the middle 70s north to upper 70s southern
through 11/14z...surface cold front will stall vicinity of ksua-Kobe. S of
kvrb-Kobe...surface wind light/variable patchy MVFR visibilities/ceilings in br...local LIFR
visibilities/ceilings in fog. North of kvrb-Kobe...N/NE surface wind around 10kts ceilings between
fl015-025 tempo below fl010 through 11/12z.
Between 11/14z-11/24z...NE surface wind 8-12kts. North of kmlb-kism...ceilings between
fl020-030. S of kmlb-kism...ceilings between fl040-060.
After 12/00z...north surface wind around 4-8kts. North of kvrb-Kobe ceilings between
fl010-015 tempo below fl005...patchy MVFR visibilities in br. S of kvrb-Kobe
ceilings between fl020-030.
today-tonight...a cold front will stall over the Central Peninsula
today...allowing a moderate to fresh north/NE breeze to diminish 15kts
or less...continuing into the overnight period. Winds will refreshen out of
the north in the predawn hours as the strong Post frontal hi pressure ridge
builds across the Ohio/Tennessee River valleys. The nerly component will push a
2-3ft swell into the local Atlantic...maintaining 3-4ft seas nearshore and
4-5ft offshore...up to 6ft in the Gulf Stream north of Sebastian Inlet.
Scripps buoys measuring seas less than 3ft...but C-man stations are
indicating winds between 15-20kts north of Sebastian Inlet. Will keep the
cautionary statement for the central/northern coastal zones.
Stronger northerly flow expected Thursday as high builds into the
southeast. 7 mb pressure gradient from jax-mia will support winds up
to 20-25 knots with some gusts to around 30 knots. Seas will build
to 8-10 feet in the Gulf Stream. Wind will veer to east on Friday with
winds from 15 knots northern waters to 20 knots southern waters. Seas will
remain elevated offshore and across the southern waters. Wind will veer
to southerly Saturday near 15 knots with seas 3-4 near shore and 5-6
feet well offshore. The front will move toward the waters Sunday with
offshore flow into early afternoon. The highest seas will remain
across the offshore waters up to around 5 feet.
Climate...a record high temperature of 85 degrees was set at
Melbourne on Tuesday. This broke the old record of 84 previously set
in 2012...1994... 1967 and 1947.
Preliminary point temps/pops...
dab 75 62 71 52 / 20 20 20 10
mco 80 62 74 53 / 20 20 20 10
mlb 79 65 76 62 / 20 20 20 10
vrb 80 63 78 64 / 20 20 30 20
Lee 78 60 71 50 / 20 20 10 10
sfb 79 62 72 53 / 20 20 20 10
orl 79 62 73 54 / 20 20 20 10
fpr 81 64 78 64 / 20 20 30 20