Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Melbourne Florida
1000 am EDT Tuesday Aug 4 2015
Current...analysis of surface metars/visible imagery shows the surface-1km ridge
axis running west-northwest from about ksua to north of Kobe to ktpa south-southwest-SW
winds cover all but the southern 3 cos...where flow is light. Morning
radiosonde observations indicate higher mean precipitable waters locally...about 2.0" with 1.9" at
tbw/mfl. Much deeper moisture noted at kjax (2.3") closer to the
departing weak surface low which had been across north ctrl Florida this time
Monday. Looking aloft...the Florida Peninsula lies to the east of a h50
col/deformation zone...which has been drifting westward allowing middle level
ridge axis to nudge westward and into the coast. North-north-northeast h25 pattern looks
neutral west/r/T any possible weak contribution to uvm/forcing.
Remainder of today...MOS guidance and mesoscale model output favor
the northern County Warning Area for diurnal convection...although the mesoscale models are
somewhat anemic in overall quantitative precipitation forecast and coverage of higher dbz cells.
With the middle/upper pattern neutral to marginally negative for weak
forcing...would expect near to slightly below normal coverage of
diurnal convection. Wcsb may be a bit more more active (as it is
climatologically) with less initial action along ecsb. We may
have to wait for additional boundary interactions (sea/lake/outflow)
later in the afternoon to see sig coverage over the eastern side of the
peninsula. All in all...don't see much to argue with the current
pop distribution of 30 S-se/40 N-NW.
Aviation...best chance for ts today north of ism-tix...although
with the current probability of precipitation...having tempo ts for the north/interior
aerodromes may turn out to be a bit pessimistic. Timing looks OK
with activity holding off until late afternoon. Will monitor radar and
visible Sat trends to see if keeping the temperatures groups in for the 18z
package will be warranted.
Marine...current buoy and C-man observation indicate S-SW flow of around
10-12kt with 1-2ft seas near shore and 2-3ft well away from the
coast. Other than removing small area of 3-4ft seas through middle
morning well offshore Volusia...fcst/grids look fine.
Previous discussion... /issued 310 am EDT Tuesday Aug 4 2015/
Tonight...some evening convection should be favored across Osceola/
southeast Orange and northern Brevard counties with late day boundary interactions.
Will keep a low shower/thunderstorm chances for these areas southeast toward
the Treasure Coast into the evening. Otherwise...expect skies to
become partly cloudy to mostly clear overnight. Lows will in the
lower to middle 70s.
Wed-Thu...Atlantic subtropical ridge axis lifts back north across
the region into middle week. A more normal summertime convective
pattern is expected each day with isolated to scattered showers and
storms developing along the sea breeze boundaries and increasing in
coverage with any boundary collisions over the interior. Have probability of precipitation
ranging around 30-40 percent along the coast and 40-50 percent
inland. Model soundings indicate some drier air aloft that may lead
to a few stronger storms each afternoon. Relatively weak west/SW
steering flow may allow any storms that develop over the interior to
move back toward the coast into the evening hours before convection
Temperatures expected to be near normal with highs around 90 degrees
along the coast to low 90s over much of the interior. Lows will
range from the low to middle 70s.
Fri-Mon...models continue to show middle level short wave trough shifting from
the Ohio/Tennessee Valley toward the middle Atlantic coast into late week/early
weekend. This feature helps develop low pressure near the middle
Atlantic that lifts north/NE along the eastern Seaboard with trailing
frontal trough extending across the southeast states this weekend.
This boundary and lingering u/l trough along the eastern coast will
shift subtropical ridge axis southward and lead to a deeper offshore
flow across central Florida. Low level west/SW winds should be just weak
enough to allow the East Coast sea breeze to form each after...
especially south of the cape but it will likely be delayed with
little inland movement.
Sufficient moisture and instability expected for scattered showers
and storms to develop each after and push eastward over the region.
Any storms/outflow boundaries that interact where East Coast sea
breeze develops will lead to a few stronger storms near the coast.
Highs will continue to reach the low 90s most areas with lows in the
Aviation...lowered rain showers/thunderstorms and rain to prob30 groups for interior
terminals with rain chances in the chance category expected this afternoon.
Expect any convection developing in the middle to late afternoon to stay
mainly west of terminals from kmlb-ksua as East Coast sea breeze moves
inland. Mainly VFR overnight past 00z.
Marine... morning winds across the offshore waters will be around
15 knots with seas 3-4 feet so will lower scec headlines. Winds will
decrease to 8-12 knots this afternoon but should increase some overnight
to 10-15 knots. Seas will slowly drop and average 2 feet nearshore to
3 feet offshore late.
Wed-Sat...ridge axis will lift near to just north of Lake Okeechobee
by middle week before it shifts back southward Fri-Sat. S/southeast winds
become S/SW by late week with wind speeds expected to remain less
than 15 knots. Seas will generally range from 1-3 feet. A relatively
weak west/SW steering flow will be present each after with a few stronger
storms potentially pushing offshore each after/early evening.
Preliminary point temps/pops...
dab 89 73 91 74 / 40 20 30 20
mco 90 74 93 75 / 40 20 40 30
mlb 90 74 89 76 / 30 20 40 20
vrb 89 73 90 74 / 20 20 40 20
Lee 90 75 92 77 / 40 10 40 20
sfb 90 74 93 75 / 40 20 40 30
orl 90 76 93 76 / 40 20 40 30
fpr 90 72 90 74 / 20 20 40 20