Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Lake Charles la
701 am CDT Friday Aug 26 2016
26/12z taf issuance.
ample moisture remains over the region this morning, resulting in
widespread clouds and patchy fog. Low stratus was producing
IFR/LIFR cigs at the la terminals along with MVFR vsby reductions
in fog. Expect cigs/fog to lift through 14z. Kbpt was reporting
MVFR cigs along with some -ra although the strongest convection is
occurring offshore. Convection is expected to gradually shift
inland with daytime heating this morning as a disturbance aloft
continues to move west. Rain chcs will be highest acrs se Texas then
decreasing to the east, so carried an aftn tempo group at kbpt,
prob30 at klch and thunderstorms in the vicinity at klft/kara/kaex. Outside of convection,
expect VFR to prevail with scattered/broken mid and high cigs and Ely winds
less than 10 kt.
Previous discussion... /issued 439 am CDT Friday Aug 26 2016/
latest upper air analysis from 26/00z shows height falls occurring
at klch at 500 mb and 70h as center of the mid/upper level ridge has
moved further to the northeast and centered over the southern
Appalachians. Moisture analysis at 26/00z showed high
precipitable water over the forecast area with precipitable water value over
2.25 inches and mean relative humidity over 80 percent. The 26/07z GPS-met data,
continued to show precipitable water values between 2.0 and 2.25 inches across
the immediate area. However, some drier air was noted across the
Gulf south on water vapor and GPS-met data just east of the
forecast area showed precipitable water values less than 1.8 inches.
Showers and thunderstorms are noted on radar over the coastal
waters and into mainly southeast Texas, as an easterly wave/upper
level impulse is interacting with the moist atmosphere.
In the broader picture, satellite shows a tropical wave (invest
99l) still disorganized and centered over the Atlantic between
the southeastern Bahamas and Cuba. This feature is relatively void
of convection near the center from satellite and confirmed on
Cuban weather radars, and seems to be barely hanging on as it
moves slowly west toward the Cuba coast.
upper level ridge will continue to slide to the northeast through
the weekend becoming centered over the mid-Atlantic states. This
will allow an easterly flow to continue across the region. First
moisture surge with an easterly wave/upper level impulse will move
into Texas today. Some drier air will then briefly move in behind
it and ahead of the next system. Therefore, likely to see a
gradient across the forecast area as far as pops go. Higher pops
over southeast Texas, with just isolated pops over Acadiana.
The next impulse will move across the northern Gulf on Saturday
and into Texas late Sunday. This will again bring a surge of
moisture with precipitable water values over 2 inches. Some guidance suggests a
surface reflection of this feature in the form of a weak surface
low/trough will form over the western Gulf before moving into the
middle Texas coast. Therefore, expect highest pops near the coast
and over the coastal waters over the weekend, mainly from the I-10
corridor and south, occurring any time from early morning through
the afternoon, with possibly a break during the evening hours. However,
decent chances for at-least scattered showers and thunderstorms
will also extend inland north of the I-10 corridor, especially
during the afternoon hours.
With the high moisture content, storms that develop may produce
some locally heavy rainfall, with a quick one to two inches of
Decent moisture will be hanging around the southern portions of
the forecast area on Monday, and with a weakness aloft, a chance
for showers and thunderstorms will also continue.
Beyond that, forecast uncertainty remains and confidence in the
overall forecast is low. The main reason is the still unknown
future for the tropical wave invest 99l. As strength of that
system and how it interacts with the strength and location of the
mid-Atlantic ridge will be key. System, if it survives its
encounter with Cuba, will remain weak for today, and with that,
guidance will still likely have big problems figuring out a
solution. At this time, solutions showing a weaker system with a
more southern and western track are preferred, with low impacts
for the immediate forecast area. Since this could change, it is
advisable to keep up to date with the latest information from the
National Hurricane Center on this system through the weekend.
With the uncertainty in the forecast for Tuesday to the end of the
period, will keep using the superblend solution, and that looks
reasonable at this time, with small chances for showers and climo
coastal waters will be on the periphery of a surface ridge
extending down from the mid-Atlantic states. This will keep an
easterly flow in place today. This flow will increase some later
today and tonight as a surface trough develops over the western
Gulf of Mexico before moving into Texas on Sunday.
A good coverage of showers and thunderstorms can be expected
through the weekend, as upper level disturbances interact with
the moist atmosphere. Winds and seas will be higher near the
storms, along with cloud to water lightning, and heavy rainfall
The forecast for next week still has some uncertainty, as the
eventual out come of the tropical wave (invest 99l) moving into
the eastern Gulf of Mexico is still unknown at this time. As it
stands now, this system will have little to no impact for the
immediate coastal waters. All mariners are still advised to keep
updated on this system through the weekend.
Preliminary point temps/pops...
aex 92 73 92 74 / 20 10 40 20
lch 91 75 88 76 / 30 20 50 40
lft 92 75 89 75 / 20 20 50 30
bpt 90 76 88 76 / 60 30 60 40