Scientific Forecaster Discussion
fxus62 kmlb 190907
Area forecast discussion
National Weather Service Melbourne Florida
407 am EST sun Feb 19 2017
Today-tonight...lingering rain chances as a low amp short wave
trof extending from the srn appalachian to the NE Gomex pushes
into the west Atlc. A band of relatively high moisture will ride
ahead of it...h100-h70 mean relative humidity values btwn 70-80pct...pwat values
generally btwn 1.25"-1.50". Mid lvl support will come in the form
of an 850 mb-h30 vort Max over the Florida Big Bend/southeast GA, as well as a
noteworthy mid lvl thermal trof extending from the Carolinas into
the ern Gomex.
Isold shra dvlpmnt along the Nature Coast over the past few hrs
supports small pops areawide. However, an 80-100kt h30-h20 jet
streak pushing acrs the Florida Peninsula will place much of the County Warning Area
under its descending left exit quad, leaving the LCL airmass devoid
of upr lvl support. Furthermore, the zonal nature of the mid/upr lvl
flow will carry the bulk of the moisture/instability into the Atlc
fairly quickly. Should see precip end from sunrise-60 northward by
midday. Will hold low pops along the Treasure Coast/lake-o region
thru late aftn as the trajectory of the moisture band suggests that
region will be the last to clear out.
Hi pres will nose into the east Gomex in the wake of the departing
short wave, then will pinch off into an independent anticyclone over
the deep south as the shortwave deepens east of the Bahama bank.
H100-h70 mean flow will respond by shifting from a westerly flow at
daybreak, to northwest by mid aftn, then north/NE overnight. However, the
source region for the Post trof airmass is the deep south/lwr MS
valley, while the short duration of the north/northwest flow will limit the
duration of meaningful cool air advection this aftn. Onshore flow
overnight will then push modified ocean air acrs the Central
Peninsula. Temps will remain abv avg...maxes in m70s/l80s along the
coast, l/m80s interior. Min temps u50s/l60s along the coast, M/u50s
Mon-Tue...the local weather during this period will be dominated by
a rather high amplitude upper ridge whose N/S axis will be located
over the eastern Gulf of Mexico on Mon, then transitioning over the
Florida Peninsula Mon night, and then east of the peninsula for Tue as
it dampens. At the surface, N/S elongated high pressure will
sprawl across the east-Continental U.S. And also transition east during the
period. Local NE winds will veer maritime east by late Mon and thru
Tue. Rain chances will be minimal and too low to mention...except
for a few onshore moving showers overnight Tue into Wed morn along
the immediate space/Treasure coasts. Max temps in the l80s and
min temps u50/m60s.
Mid-late week...per GFS, a closed upper low moves oddly off the
Lower Texas coast out across the Gulf of Mexico during the mid-week
toward the Florida Straits as it fills. The gefs ensemble mean currently
supports this (change of) thinking. More so, the European model (ecmwf) Happy to
do same but keeps a closed feature for this otherwise anomalous
pattern. Thus, a respectful amount of uncertainty remains
prudent here relative to the strength/track of this low-latitude
storm system. Even so, looks like unsettled weather moving toward
the eastern Gulf mid-late week with the distribution of
convective potential and related hazards highly dependent on the
aforementioned. It is enough at this point to indicate
thunderstorm chances for ecfl Wed-Thu, but a watchful eye will be
needed for the evolving and unexpected. Pops 30-40 percent
areawide Wed, but toward Lake Okeechobee and the marine waters
Thu. Some lingering pops afterward before clearing out during the
weekend courtesy of a more traditional frontal system. Max temps
u70s/l-m80s with min temps l/m60s.
sfc winds: thru 19/13z...W/SW 3-5kts. Btwn 19/13z-19/15z...bcmg west/northwest
7-11kts. Btwn 19/23z-20/02z...bcmg north/NE 5-8kts.
Vsbys/wx/cigs: thru 19/14z...slgt chc MVFR cigs/vsbys in -ra...north of
kism-ktix areas MVFR/LCL LIFR vsbys in br. Btwn 19/14z-19/18z...S of
kism-ktix slgt chc MVFR shras.
today-tonight...a short wave trof will push off the east Florida coast
today, allowing high pres ridge to nose its way into the ern Gomex
from the Florida Straits. The ridge will pinch off into an independent
anticyclone and drift into the deep south as the departing trof
deepens east of the Bahamas. Shifting winds thru the day, moderate
to fresh wrly breeze at daybreak diminishing to a gentle to moderate
north/northwest breeze by mid aftn, then slowly veering north/NE overnight. Seas 2-
3ft nearshore and 3-4ft offshore. Rough short pd wind chop possible
as the offshore winds veer thru due north and buffet up against the
srly Gulf Stream.
Mon-Tue...local NE wind flow around the southern periphery of large
high pressure over the east-Continental U.S. Will gradually veer to the east as the
feature shifts out over the western Atlantic by Tue. Speeds 10-15
knots with seas well below cautionary levels. A slight chance of
showers Tue evening continuing through the overnight.
Wed-Thu...reinforced onshore wind flow for Wed as east fetch increases
opposite a low-latitude storm system developing in the central Gulf.
Moisture will steadily gather in proximity bringing increased
shower/storm chances to the forecast as winds become southeast for Thu.
Seas 3-4 feet supported by speeds 10-15 knots.
Preliminary point temps/pops...
dab 77 58 77 60 / 20 0 0 10
mco 83 58 81 61 / 20 0 0 0
mlb 79 60 78 63 / 20 0 0 10
vrb 80 60 79 63 / 20 0 0 10
Lee 82 56 81 60 / 20 0 0 0
sfb 81 58 80 60 / 20 0 0 0
orl 83 59 80 61 / 20 0 0 0
fpr 80 60 79 62 / 20 0 0 10