Special Weather Statement, NWS Melbourne, FL

Area Forecast Discussion
National Weather Service Melbourne FL
945 AM EDT Thu Jul 20 2017

.DISCUSSION...

RAP40 analysis shows central FL under a weak H100-H70 trough with
the Atlc ridge axis blanketing south FL and the Bahama Bank. Lcl
wind profilers map the trough axis quite well through the sfc-5KFT
lyr with N/NW winds at KJAX/KTBW veering to S/SW at KMFL/KMLB/KXMR.
Early morning ocean convection reflecting the axis as well...on the
ascending right flank of the trough, Gulf Stream convection has been
very active in the predawn hrs...on its descending left flank, GOMex
convection has been much more subdued. W/NW flow thru the H85-H30
lvl has been pushing a few scraps of debris clouds from the west
coast convection acrs the region btwn I-4 and Lake-O, but these
should have little impact on sfc heating.

Morning RAOBS indicate slightly drier air has worked its way into
the north FL Peninsula as PWats along and north of I-4 were in the
1.75"-2.00" range. However, sfc dewpoints in the M/U70s indicate
overall available moisture remains plentiful, especially south of I-
4 where PWats remain largely AOA 2.00". Mid lvl temps have changed
little in the past 24hrs...H50 temps btwn -6C/-7C temps are typical
for midsummer, but the H70 readings btwn 9.0-9.5C indicates thermal
ridging has strengthened a touch. However, this will do little more
than delay the onset of diurnal convection as overall thermodynamic
instability remains high:  Fcst CAPE arnd 2000J/kg at KJAX,
increasing to arnd 2500J/kg from KTBW/KXMR southward.

H70-H50 lapse rates arnd 5.5C/KM along and north of I-4 and arnd
6.0C/KM over the Treasure Coast/Lake-O region suggest strongest
activity will be south of I-4 this aftn. Latest round of sct-nmrs
shras/tsras should begin firing around midday along the east coast
sea breeze as sfc temps reach their convective triggers...U80s as
measured by the 20/12Z RAOBs.

Inland progression of the sea breeze will be slow due to the
westerly H100-H70 flow, but convection will largely follow its
propagation, forming along mesoscale bndry collisions as they push
inland. Likely PoPs (60-70pct) remain a good bet given the available
moisture and instability with the strongest activity expected along
the Florida Turnpike south of I-4. KTBW/KXMR RAOBs show a spike in
H50 dewpoint depressions (15-20C) with a noteworthy pocket of dry
air thru the H50-H30 lyr. This will support strong wind gusts and
frequent CG lightning strikes. Weak westerly steering flow will
increase the potential local heavy rain, as well as blowback debris
clouds/precip along the coast late aftn/early evng. Max temps
U80s/L90s along the coast...L/M90s interior.

&&

.AVIATION...Thru 21/12Z.
Sfc winds: Coastal sites N of KTIX...btwn 20/15Z-20/17Z W/SW 4-7KTS
bcmg E/NE 6-10KTS...btwn 21/02Z-21/05Z bcmg S/SW AOB 3KTS. Coastal
sites S of KTIX btwn 20/15Z-20/17Z W/SW 4-7KTS bcmg E/SE 8-12KTS...
btwn 21/02Z-21/05Z bcmg S/SW AOB 3KTS. Interior sites...thru 20/16Z
W/NW 3-6KTS...btwn 20/16Z-20/18Z bcmg E/NE 5-8KTS...btwn 21/01Z-
21/04Z...bcmg S/SE AOB 3KTS.

Vsbys/WX/Cigs: Btwn 20/16Z-20/20Z...sct MVFR shras/isold IFR tsras.
Btwn 20/20Z-20/24Z...nmrs MVFR shras/IFR tsras...slgt chc LIFR
+tsras with sfc G35KTS. Btwn 21/00Z-21/02Z...S of KMLB-KTIX chc MVFR
shras/slgt chc IFR tsras.

&&

.MARINE...
Atlc ridge axis positioned over south FL/nrn Bahamas will combine
with a weak trough over central/north FL to generate a light to
gentle S/SW breeze over the lcl Atlc. Winds bcmg onshore near the
coast by midday with the formation of the east coast sea
breeze...E/NE north of Cape Canaveral, E/SE south of the Cape. Seas
AOB 2FT nearshore and 2-3FT well offshore. Sct to nmrs showers and
sct t-storms over the Gulf Stream thru early aftn, diminishing by
mid aftn.

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.

&&

Short Term Update....Bragaw
Aviation/Impact WX...Glitto

Hazardous Weather Outlook
National Weather Service Melbourne FL
1151 AM EDT Thu Jul 20 2017

AMZ550-552-555-570-572-575-FLZ041-044>047-053-054-058-059-064-141-
144-147-210000-
Flagler Beach to Volusia-Brevard County Line 0-20 nm-Volusia-
Brevard County Line to Sebastian Inlet 0-20 nm-
Sebastian Inlet to Jupiter Inlet 0-20 nm-Flagler Beach to Volusia-
Brevard County Line 20-60 nm-Volusia-
Brevard County Line to Sebastian Inlet 20-60 nm-
Sebastian Inlet to Jupiter Inlet 20-60 nm-Inland Volusia County-
Northern Lake County-Orange-Seminole-Southern Brevard County-
Osceola-Indian River-Okeechobee-St. Lucie-Martin-
Coastal Volusia County-Southern Lake County-
Northern Brevard County-
1151 AM EDT Thu Jul 20 2017

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL FLORIDA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

.THUNDERSTORM IMPACT...
High atmospheric moisture will lead to another round of scattered
to numerous lightning storms this afternoon and early evening.
Storms will continue to form near the east coast into the mid
afternoon, then coverage will increase inland through the late
afternoon. The highest storm coverage is expected from Lake
Okeechobee and the Treasure coast reaching northwest near the
Kissimmee River, the metro Orlando area and into Lake County.
Storms will be more scattered to the north and east of this area.
A few strong storms containing wind gusts up to 50 mph, small hail,
frequent to excessive lightning strikes, and very heavy rain are
expected late this afternoon.

.FLOOD IMPACT...
Locally heavy rainfall accumulating up to 2 to 3 inches will
cause temporary flooding of some roads and low lying areas. The
greatest threat for localized flooding will be from the Orlando
metro area southward to Lake Okeechobee and in areas that have
seen multiple rounds of heavy rain over the past several days.

.MARINE THUNDERSTORM GUST IMPACT...
Scattered to numerous lightning storms are expected to impact the
intracoastal waters and inland lakes this afternoon. Gusty winds
of 35-40 knots and frequent lightning strikes are the main hazards.
Boaters are reminded that sudden changes in wind speed and direction
can occur well ahead of the heaviest rain from a thunderstorm.

.RIP CURRENT IMPACT...
A small east swell will generate a moderate rip current threat
along the beaches of east central Florida. Always swim within
sight of a lifeguard.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.
Scattered to numerous lightning storms are expected each afternoon.
The primary threats will be dangerous cloud to ground lightning
and gusty winds. Slow moving storms will also produce very heavy
rains resulting in temporary flooding of some roads and poor
drainage areas.

An east swell will produce a moderate risk of rip currents at
the beaches.

.SPOTTER INFORMATION STATEMENT...
Spotters are requested to monitor the weather and self activate
if needed. In addition, please report any rainfall amounts greater
than 3 inches to the National Weather Service.

Ulrich/Glitto

Special Weather Statement
National Weather Service Melbourne FL
252 PM EDT THU JUL 20 2017

FLZ147-201930-
Northern Brevard County FL-
252 PM EDT THU JUL 20 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN BREVARD COUNTY UNTIL
330 PM EDT...

At 252 PM EDT, Doppler radar was tracking a strong thunderstorm over
Mims, moving southeast at 10 mph.

Winds in excess of 40 mph will be possible with this storm.

Locations impacted include...
Titusville, Mims, Turnbull, Aurantia and Lagrange.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 2861 8072 2854 8091 2863 8097 2868 8097
      2878 8080
TIME...MOT...LOC 1852Z 320DEG 8KT 2867 8088

Weitlich