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View Full Version : From Jeff this morning


Bozo
01-12-2005, 09:44 AM
Powerful upper level storm system plowing toward TX. Impressive
pressure falls this morning over NW TX where surface pressure have
tumbled to 29.37in. Pressure gradient has greatly increased with Waco
gusting to 40 and DFW gusting over 40 in the last hour. Strong winds
over W TX sustained above 30mph with gust over 50mph will continue
through the afternoon. Locally, gust to 40mph will be possible along
and west of a College Station to Katy to Freeport line.

AM soundings show a large cap in the 800mb-700mb layer nearing 15-20C.
This capping will keep a lid on convection within the warm sector for
most of the day. Strong upper level forcing along with short wave
cooling will arrive by late afternoon and begin to erode the capping.
Low level forcing along the front should be able to produce enough
lift to break the cap by early evening and fire off a line of
thunderstorms. AM profilers and soundings show low level jet of 45-
55kts just off the surface and then a mid level jet of 120kts+ from
the SW. Linear forcing along the frontal boundary will produce a
squall line feature this evening. Wind energy will come to the surface
in downdrafts and microburst and in any line bow segments. Damaging
winds of 60-80mph will be the main threat. Instability will be limited
to near 500-1000 J/kg of CAPE and this should keep a low tornado
potential in an otherwise very favorable sheared profile for
tornadoes.

Degree of capping to the SW of Houston may prevent much more than a
line of thunderstorms or showers. The greatest severe threat is north
of I-10 although SPC has the whole area outlooked currently.

Guess this would qualify as a probable bust for chasing but I'll be out and about for awhile this evening anyway. Latest I read from NWS puts squall line in Houston proper area around midnight, maybe I can catch its development further to the NW if I time it right. More than likely just end up grumpy at the end of what looks to be a long evening.

DANG! I hate when these wretched things come through at night!

Bozo
01-12-2005, 10:54 AM
UPDATED HWO for Houston/Galveston just out:
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1020 AM CST WED JAN 12 2005

TXZ163-164-176>179-195>200-210>214-226-227-235>238-122200-
AUSTIN-BRAZORIA-BRAZOS-BURLESON-CHAMBERS-COLORADO-FORT BEND-GALVESTON-
GRIMES-HARRIS-HOUSTON-JACKSON-LIBERTY-MADISON-MATAGORDA-MONTGOMERY-
POLK-SAN JACINTO-TRINITY-WALKER-WALLER-WASHINGTON-WHARTON-
1020 AM CST WED JAN 12 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST TEXAS.

...WIND ADVISORY IN EFFECT UNTIL 4 PM NORTHWEST OF A COLUMBUS
TO HEMPSTEAD TO MADISONVILLE LINE...

...SQUALL LINE WITH HIGH WINDS EXPECTED BETWEEN 11 PM AND 5 AM...

.DAY ONE...THIS AFTERNOON AND TONIGHT.
STRONG SOUTHERLY WINDS ARE EXPECTED THIS AFTERNOON. A TIGHTENING
PRESSURE GRADIENT IN RESPONSE TO A DEEPENING LOW OVER WEST TEXAS WILL
HELP PRODUCE SUSTAINED SOUTH WINDS AROUND 25 MPH NORTHWEST OF A
COLUMBUS TO MADISONVILLE LINE. WIND GUSTS OF 30 TO 35 MPH ARE ALSO
POSSIBLE. SOUTH WINDS OF 15 TO 25 MPH ARE EXPECTED SOUTH OF THIS
LINE.

THERE IS A SLIGHT RISK OF SEVERE WEATHER ACROSS ALL OF SOUTHEAST
TEXAS TONIGHT.

A LINE OF STRONG TO SEVERE THUNDERSTORMS WILL DEVELOP OVER NORTH
TEXAS THIS EVENING. THE SQUALL LINE WILL BACKBUILD TO THE SOUTHWEST
AS THE SYSTEM PUSHES EAST. A LINE OF SEVERE STORMS WILL APPROACH
THE COLLEGE STATION AREA BETWEEN 11 PM AND 1 AM...HOUSTON METRO
BETWEEN 1 AND 3 AM AND ACROSS THE COAST BETWEEN 4 AND 6 AM.

THERE IS TREMENDOUS WIND ENERGY ASSOCIATED WITH THIS SYSTEM. AT THIS
TIME...IT APPEARS THE PRIMARY SEVERE HAZARD WILL BE STRAIGHT LINE
DAMAGING WINDS. THERE IS SUFFICIENT SHEAR...SO ISOLATED SHORT LIVED
TORNADOES ARE ALSO POSSIBLE. SUFFICIENT INSTABILITY WILL BE PRESENT...
SO DESPITE UNSEASONABLY WARM FREEZING LEVELS...HAIL WILL REMAIN
A THREAT. FLOODING RAINS ARE NOT EXPECTED AS THIS COMPLEX OF STORMS
WILL MOVE EAST RATHER QUICKLY.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.
HAZARDOUS WEATHER IS NOT EXPECTED.

.SPOTTER INFORMATION STATEMENT....
SPOTTER AND EMERGENCY MANAGEMENT ACTIVATION WILL LIKELY BE REQUIRED
TONIGHT.

$$

Bozo
01-12-2005, 03:22 PM
.DISCUSSION...
A COLD FRONT ACROSS SOUTHERN KANSAS WILL HEAD SOUTH TONIGHT. THE
FRONT IS EXPECTED TO MOVE RAPIDLY ACROSS EAST TEXAS OVERNIGHT AND
EXIT THE AREA BEFORE SUNRISE THURSDAY MORNING. DYNAMICS ARE
IMPRESSIVE WITH THIS SYSTEM. 850 MB CONVERGENCE IS STRONG AND THE
LOW LEVEL JET IS HOWLING AT 50-60 KNOTS. PLENTY OF SPEED SHEAR TO
WORK AVAILABLE. THE AREA LIES IN A STRONG 130 KT RIGHT REAR QUAD.
MODELS ARE FORECASTING STRONG OMEGA FIELDS AND LAPSE RATES OF 7-7.5
DEGREES CELSIUS. FCST MODEL SOUNDINGS ALSO REVEAL SOME IMPRESSIVE
INSTABILITY WITH LI'S -3 TO -5...CAPES AOA 1500 AND HELICITY VALUES
NEAR 200. THE HODOGRAPH HAS A NICE TURN TO IT...AND IF WE CAN GET
SOME DISCREET CELLS AHEAD OF THE LINE...WOULD NOT BE SURPRISED TO
GET A FEW TORNADO REPORTS. THIS SYSTEM IS PROGRESSIVE AND ONLY BRIEF
HEAVY RAIN IS EXPECTED.THE FRONT IS EXPECTED TO REACH CLL BETWEEN
05-06Z...IAH 07-09Z AND GLS 9-11Z. WILL KEEP SEVERE WORDING IN THE
ZONES TONIGHT AND WILL RE-ISSUE THE HWOHGX.

Bozo
01-12-2005, 04:22 PM
Strong to severe squall line expected tonight with damaging winds.

Powerful upper level storm system centered near Dalhart, TX will move
ESE along the Red River tonight blasting a cold front through the
area. VAD profiles show a 70kt low level jet roaring NNE across the
area this afternoon with a 140kt mid level jet max approaching SW TX
from old Mexico. Capping remains stout on the animated soundings from
OU, but mid level cooling and strong dynamical forcing should erode
much of this inhibition by mid evening. Strong frontal forcing and
good vertical motions should result in rapid squall line formation as
the front moves into the area. In fact visible images are already
showing towering cumulus over W TX along the front.

Front should reach CLL around midnight, HOU between 2-4AM and the
coast between 4-6am. Powerful 140kt jet max punching into the backside
of the squall line will tranport some momentum to the surface within
downdrafts. Damaging winds of 55-65mph are possible along the leading
edge of the line with 80-90mph or greater winds within bows and
supercells within the line. Given the tremendous shear profiles any
cells that fire ahead of the main line will go tornadic quickly.
Luckily we do not have much instability due to cloud cover or we would
be looking at a major tornado outbreak.