Scientific Forecaster Discussion

Return to Local Conditions & Forecast
Area forecast discussion 
National Weather Service Melbourne Florida
336 PM EDT Thursday Apr 17 2014


.Wet through Saturday with potential for locally heavy rainfall
especially along the coast...

..hazardous boating conditions through this weekend and into early
next week...

Current...high pressure over the Middle Atlantic States northward
ridges to the northeast Gulf of Mexico. The northeast to east
windflow around the southeast area of the high was pushing marine
stratocu ashore east central Florida. The 915mhz vertical wind
profilers at the space center bear this out with easterly 20 to 25
knots winds from just off the surface to around 5000 feet/approx
850mb. The winds then make an abrupt shift to the west at around
6500 feet and remain out of the west to 10000 feet which is the
upper limit of the 915mhz recording heights. The frontal boundary
that was analyzed as a diffuse warm frontal boundary just south of
Lake Okeechobee this morning has moved to just north of the lake.
Weather radars detecting scattered showers and lightning storms over
South Florida with more showers and storms along the frontal
boundary as it slowly lifts north across the southern portions of
east central Florida.

Tonight...model time height cross sections were indicating that the
current conditions should continue overnight as the frontal boundary
lifts slowly northward as a warm front associated with a developing
area of low pressure in the north central Gulf of Mexico.
Precipitable water values between an inch and a half and 1.9 inches
and the lift provided by the southwest to west winds moving over the
lower layer easterly winds should give US at least chance...30-50
percent... of overnight rains.

Friday...the newly formed warm front associated with the low
pressure system in the north Gulf of Mexico lifts northward as the
low tracks off to the northeast crossing North Florida and into the
Atlantic east of Georgia with a trailing cold front crossing over
Florida overnight Friday. The brisk south to southwest windflow
ahead of the cold front will make for a breezy Friday with rain
chances ranging from around 60 percent southern areas to 80 to 90
percent northern areas. Have kept thunderstorms in the Friday
forecast as colder...-10c to -12c...middle level air moves overhead
steepening middle level lapse rates and strong middle level impulse moves
overhead during the day Friday. Temperatures range from the middle 80s
southern areas to low 80s northwest Volusia and Northeast Lake

Friday night...the cold front is expected to sweep across central
Florida overnight Friday and Saturday morning clearing central
Florida Saturday afternoon. Lows Saturday morning middle and upper 60s.

Saturday-Saturday night...southwest to west winds advecting Gulf
moisture across the peninsula keep rain chances in the 30 to 50
percent area. Highs range should range from the upper 70s Northwest
Lake County to the middle 80s on the in the areas on the leeward side
of Lake Okeechobee. Northwest winds overnight Saturday bring cooler
air into central Florida. Overnight Saturday/sunrise Sunday morning
lows in the middle and upper 50s sunrise Sunday morning.

Previous zones discussion

Today-tonight...Post frontal dry airmass remain fairly pervasive
across the region...especially across the interior and Volusia
County where dewpoints are still in the middle-upper 50s.

Models have so far been very gung Ho in lifting the old frontal
boundary/enhanced moisture back north...but it appears that the
northward trend may be starting as one heavy rainband set up earlier
this evening across Broward County that has since dissipated.
Current analysis shows a band of enhanced low level moisture from
Brevard/Osceola counties southwards coincident with an area of wind
convergence in the 1000-850mb layer. This is where radar is also now
picking up on a recent upswing in shower coverage.

Local WRF model shows a band of enhanced precipitation around daybreak over
the Treasure Coast...but hrrr model keeps this activity more over
South Florida until later. Its tough to say where or if any locally
heavy bands may set up until they do...but just ahead of/along warm
front would be the best bet. Do expect an increase in shower
frequency towards daybreak across the Treasure Coast.

Frontal remnants and best isentropic lift will move back to the
north across central Florida through the day...accelerating into
North Florida tonight as upper level shortwave swings eastwards and
surface low develops across the Gulf. Have tapered back rain chances
to 20 percent northern interior to 60 percent Okeechobee/Treasure
Coast based on current trends/model forecast. Could see a few
periods of heavy rain along the coast today...before the best rain
chances will lift north of the region later tonight.

Though it will be breezy again this doesn't appear
that speeds/gusts will be quite as high as yesterday so have not
issued a lake Wind Advisory. However conditions will still remain
choppy on area lakes.

Coastal highs will be highly dependent on cloud cover and precipitation
timing...but overall expected anywhere from low 70s along Volusia
coast to upper 70s/around 80 in Brevard/Treasure Coast. Interior
temperatures in the upper 70s and low 80s. Mild overnight as flow becomes
more east-southeast with lows in the upper 60s interior/around 70s

Fri-sun...the overall trend of the short range forecast is decidedly
slower and wetter into Sunday. Strong southern stream short wave
trough will move east along the eastern Gulf Coast before pinching off
into a closed middle-upper low in vicinity of the Florida/al/GA tri-state region Friday
night. The closed low will then drift slowly east somewhere between the
Florida/Georgia border and peninsular North Florida on Sat...easing offshore Sat
night and drifting farther offshore and away from the Florida East Coast
on sun.

At the surface...available model guidance has converged toward a more
agreeable (slower) solution...although the GFS continues to be the
fastest. Surface frontal wave spins up into a low and tracks across the
northestern Gomex Friday...with the surface and middle/upper level lows becoming
vertically stacked by Friday night over North Florida. Surface warm front lifts
northward through central Florida during the morning...which should take
widespread stratiform rainfall northward across north FL/GA...while ecfl
breaks out into the warm sector of the Gomex low. Deep layer S-SW
flow with precipitable waters around 1.75" will lead to widespread showers/storms
with the potential for a band of stronger storms to reach ctrl Florida
from the Gomex (n/west of I-4) around sunset (give or take) and
continue to drop southeastward through the evening hours.

Surface low will be very slow to move across the state Friday night...and
then linger offshore the Florida East Coast throughout Sat. Sufficient
wrap around moisture will exist for scattered to numerous showers...and even
some storms given the cold h50 temperatures underneath the h50 low ovhd.
Expect lingering showers Sat night/Sunday in cool/moist nearly flow
on back side of the low...which will be grudgingly slow to put space
between itself and Florida. Coverage/intensity should be rather low.

Mon-Wed...weak high pressure finally settles in toward Florida early next
week...and drying conds out. There are some suggestions of a weak
frontal trough and ascd moisture band taking a glancing shot at North
Florida Tuesday-night into Wednesday...but will not get too involved in dissecting
day 6-7 probability of precipitation given the more sig weather in days 1-3.


Aviation...prevailing MVFR through the evening and overnight as a
warm front and with areas of light to moderate rain moves slowly up
the peninsula. Prevailing VFR overcast Friday as the warm front clears
and we are in the warm sector.

Previous aviation

Moist and cloudy through the period...though overall it
appears most locations will remain just inside VFR with prevailing
ceilings fl035-050. Coastal sites will be more likely to see MVFR ceilings
fl020-030. Isolated rain showers moving onshore into areas south of kvrb
through 13z...then becoming sct-nmrs. Coverage will increase from
south-north as old frontal boundary lifts back to the north through
the day. A few heavier rain showers may produce tempo IFR conditions mainly
along coastal sites. Could see prevailing IFR ceilings later tonight as
warm front lifts north of region.



Current-overnight...National oceanic and atmospheric administration buoys 009 and 010 were recording northeast
winds around 20 knots and 8 to 9 foot seas. The two scripps buoys 4
and 6nm off the coast were recording 4 and 7 feet respectively.
Northeast to east winds around 20 knots continue overnight as a slow
moving warm front works its way northward. Will keep the Small Craft
Advisory through the evening through 4am coastal issuance.

Friday...winds shift to south and southwest as the coastal waters come
into the warm sector between the warm front to the north and the
cold front in the central/eastern Gulf of Mexico. Winds decrease as
the pressure gradient in the warm sector decreases but expect to
have small craft exercise caution with 15-20kt and seas to 6ft
possibly a bit higher.

Sat-Monday (modified)... coverage of rain and storms/gusty winds will
remain marine threats into Saturday. Synoptic gradient winds will
begin to pick back up Sat afternoon as the low center moves offshore
the Florida East Coast and pgrad tightens. Seas will ramp back up to
7-10ft or a little higher Sat night through sun as west-northwest winds shift
to north and north-northeast behind the slowly departing low. Slow improvement in
winds seas Monday.


Preliminary point temps/pops...
dab 68 78 68 74 / 30 90 60 30
mco 68 82 67 79 / 30 80 60 30
mlb 72 81 71 79 / 30 60 60 30
vrb 72 81 71 80 / 30 60 60 30
Lee 66 79 65 77 / 30 90 60 30
sfb 67 82 68 79 / 30 80 60 30
orl 68 82 67 79 / 30 80 60 30
fpr 72 82 70 81 / 30 60 60 30


Mlb watches/warnings/advisories...
Am...Small Craft Advisory until 6 am EDT Friday for coastal waters
from Flagler Beach to Volusia Brevard County line out 20 nm-
coastal waters from Volusia Brevard County line to
Sebastian Inlet out 20 nm-waters from Flagler Beach to
Volusia Brevard County line 20 to 60 nm offshore-waters
from Volusia Brevard County line to Sebastian Inlet 20 to
60 nm offshore.

Small Craft Advisory for hazardous seas until 6 am EDT Friday
for coastal waters from Sebastian Inlet to Jupiter Inlet
out 20 nm-waters from Sebastian Inlet to Jupiter Inlet 20
to 60 nm offshore.



impact weather...volkmer