Mesoscale Precipitation Discussion 0751...Correction
NWS Weather Prediction Center College Park MD
1144 AM EDT Mon Sep 03 2018
Correction for location of system
Areas affected...Southeast TX
Concerning...Heavy rainfall...Flash flooding possible
Valid 031459Z - 032059Z
Summary...Bands of heavy rain are expected to shift from the coast
into interior southeast TX with time. Hourly rain totals to 3",
and additional local amounts to 5", are expected.
Discussion...A warm core low with an elongated low-level
circulation is centered northwest of Fort Hood, TX at this time.
An upper level high is allowing divergence aloft which has
sponsored an increasing degree of convection coverage this
morning. Heavy rain is occurring within its primary inflow band
along the Middle and Upper TX coasts within an area with
convergent 850 hPa inflow. Precipitable water values are ~2.5"
per GPS data. Inflow at 850 hPa is 25-30 kts per VAD wind
profiles, currently strongest in western LA, which is 2-3 times
the magnitude of the mean 850-400 hPa wind. The system's cyclonic
circulation is importing ML CAPE values of 500-2000 J/kg into
Southeast TX. Because of the high moisture content, CIN does not
exist per SPC mesoanalyses.
The guidance shows the potential of another few hours of issues
near the Southeast TX and Southwest LA coast as ML CAPE erodes due
to ongoing convection. However, recent radar imagery is showing
some filling in of convection within the ML CAPE gradient east of
Austin. While this convection is currently scattered, the degree
of low-level inflow could lead to the formation of short training
bands on occasion within interior Southeast TX west of the Big
Thicket with time as low-level inflow attempts to increase later
today. The mesoscale guidance advertises additional local amounts
of 5", which seems plausible. As the degree of convective
organization is uncertain across interior Southeast TX with time,
left the category as possible.
Roth
ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SHV...
ATTN...RFC...LMRFC...WGRFC...
LAT...LON 32139688 30869410 29749290 29649375 29269469
28869528 28229671 29209727 31319820
Last Updated: 1144 AM EDT Mon Sep 03 2018