Moisture from Lane and possible TX Flood Event

[Portastorm]

Going to have to keep an eye on moisture from Lane in the Pacific and the front that's going to impact us in Texas on Sunday-Monday-Tuesday.

What worries me is that JB tonight in his column referenced October 17, 1994. You folks in SE Texas ought to remember that one!!

Austin/San Antonio NWS is already mentioning possibility of this event in their forecast discussions.

[Johnny]

Yep, the ingredients will certainly be there. Even if we don't see a flooding event, it looks like getting rain will not be an issue.

From the Dallas/Fort Worth office:

THIS COULD BE A WIDESPREAD AND SIGNIFICANT RAIN EVENT...
WITH SOME LOCATIONS GETTING MORE THAN 2 INCHES...BUT FOR NOW HAVE
CAPPED POPS OFF AT 60 PERCENT. CLEARED THE POPS AND CLOUDS OUT
MONDAY NIGHT WITH TUESDAY THROUGH THURSDAY LOOKING RATHER NICE.

[jasons2k]

Yes, I'm watching this carefully. Jeff mentioned in his email that this setup is very similar to the events of October 1994, 1998, and 2002. However - he said the exact same thing a few weeks ago (I think it was Iliana?) and I got barely a trace of precip from the whole "event". We'll see...I could use some rain, that's for sure.

[Aslkahuna]

The only storm to send moisture into the SW US from EPAC this year was John two weeks ago.

Steve

[bob rulz]

I hope Lane draws moisture northward up here to Utah. It's rare, but it's happened before (just take a look at Olivia in 1984).

[KatDaddy]

I remember Oct 1994 well. It was one of top 3 flood events for SE TX in recent history.

TS Allison
TS Claudette
Oct 1994

Here is this mornings Forecast Disc from Houston-Galveston

000
FXUS64 KHGX 151007
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
507 AM CDT FRI SEP 15 2006

.DISCUSSION...
MOISTURE RETURN UNDERWAY WITH 70 DEWPOINTS ACROSS THE CENTRAL CWA
AND MID 60S IN HOUSTON COUNTY...PW 1.7" COAST TO 1.3" NORTH. THE
MOISTURE RETURN LIMITED BY THE PRIMARILY ESE-E FLOW IN THE LOWER
6KFT PER VWP. LEE CYCLOGENESIS...AS THE PRESSURES FALL IN
WY/CO/NE/SD TODAY WITH THE APPROACH OF THE VIGOROUS TROUGH OVER
ID/UT THE LOW LEVEL WINDS ACROSS SETX SHOULD INCREASE AND BECOME
MORE SE AND WE SHOULD EXPERIENCE A WARM AND MOIST AFTERNOON.
ISOLATED SHRA/TSRA POSSIBLE AS WEAK CONVERGENCE TRAVERSES THE
NEARSHORE WATERS AND INTO SETX THIS MORNING. DAYTIME HEATING TODAY
SHOULD ALLOW FOR A FEW AREAS REACHING THE CONVECTIVE TEMPERATURES
90-91 TO FUEL A FEW MORE SHRA/TSRA...PROBABLY BETTER CHANCES OVER
THE SOUTHWEST 1/3 OF THE REGION. RAIN CHANCES WILL CONTINUE TO
RISE THROUGHOUT THE WEEKEND AS THE POTENT NORTHERN ROCKIES SYSTEM
LIFTS ENE AND MOISTURE FROM THE GULF DEEPENS AND MID TO UPPER
LEVEL MOISTURE FROM THE PACIFIC TROPICAL STORM LANE GETS CARRIED
NORTH ACROSS MEXICO TURNING EAST AS IT GETS CAUGHT UP BY THE
SUBTROPICAL JET FLOW ROUNDING THE BASE OF THE WESTERN TROUGH.

THE FORECAST GETS MORE INTERESTING ON SUNDAY AS PW VALUES CLIMB TO
1.8 TO 2.2" AND WITH A HIGH LAYER RH THROW IN THE DAYTIME HEATING
(THOUGH HAMPERED BY CLOUD COVER) WE COULD SEE SCATTERED SHRA/TSRA
OFF AND ON DURING THE COURSE OF THE DAY. AS THE UPPER TROUGH
SHIFTS EAST THE ASSOCIATED COLD FRONT DROPS SOUTH THOUGH PRIMARILY
PACIFIC IN ORIGIN IT SHOULD MOVE INTO SETX MONDAY/EARLY
TUESDAY...ECMWF SLOWER THAN THE GFS AND WE HAVE TRENDED ABOUT 6
HOURS SLOWER THAN THE GFS. SUSPECT THAT WITH IT BEING PACIFIC IN
ORIGIN THE TAIL END OF THE FRONT MAY BE SLOWER THAN GFS PROGS
INDICATE. BUT WHETHER IT IS SLOWER OR NOT SETX SHOULD BE IN FOR A
WET AFTERNOON OR NIGHT. GIVEN THE ABOVE MENTIONED MID/UPPER LEVEL
MOISTURE THE STRONG LOW LEVEL INFLOW...MODERATE DIVERGENT UPPER
FLOW ALOFT AND MODEST INSTABILITY AT AND AHEAD OF THE FRONT AM
EXPECTING SCATTERED TO NUMEROUS SHRA/TSRA MONDAY/MONDAY NIGHT THAT
WILL BE CAPABLE OF INTENSE RAINFALL RATES. THOUGH IT IS STILL WAY
OUT THERE...MAY BE LOOKING AT A FLOOD WATCH SETUP. MAY ALSO HAVE A
MINIMAL SEVERE THREAT IF THE LOW LEVEL FLOW BACKS ONLY A LITTLE
FROM CURRENT PROGS. DRY WEATHER FOLLOWS THE FROPA TUESDAY AS SKIES
CLEAR OUT. MILD WEATHER WEDNESDAY AND THURSDAY WITH RETURN FLOW
MOISTENING UP THE PROFILE THURSDAY AND AT LEAST A SLIGHT CHANCE TO
CHANCE OF RAINFALL FRIDAY. THE SYSTEM DEVELOPING FRIDAY LOOKS MORE
SHEARED AND MAY BE SLOWER TO COME OUT AND COULD SPELL ANOTHER BOUT
OF PRECIP FRIDAY THROUGH SUNDAY.

[Extremeweatherguy]

[gboudx]

Yep, the ingredients will certainly be there. Even if we don't see a flooding event, it looks like getting rain will not be an issue.

From the Dallas/Fort Worth office:

THIS COULD BE A WIDESPREAD AND SIGNIFICANT RAIN EVENT...
WITH SOME LOCATIONS GETTING MORE THAN 2 INCHES...BUT FOR NOW HAVE
CAPPED POPS OFF AT 60 PERCENT. CLEARED THE POPS AND CLOUDS OUT
MONDAY NIGHT WITH TUESDAY THROUGH THURSDAY LOOKING RATHER NICE.

Curiously the morning AFD makes no mention of a significant rain event for NTX. I don't know if this is just a difference in writing style between the AM and PM crews, or if they aren't expecting it now.

[Portastorm]

Yep, the ingredients will certainly be there. Even if we don't see a flooding event, it looks like getting rain will not be an issue.

From the Dallas/Fort Worth office:

THIS COULD BE A WIDESPREAD AND SIGNIFICANT RAIN EVENT...
WITH SOME LOCATIONS GETTING MORE THAN 2 INCHES...BUT FOR NOW HAVE
CAPPED POPS OFF AT 60 PERCENT. CLEARED THE POPS AND CLOUDS OUT
MONDAY NIGHT WITH TUESDAY THROUGH THURSDAY LOOKING RATHER NICE.

Curiously the morning AFD makes no mention of a significant rain event for NTX. I don't know if this is just a difference in writing style between the AM and PM crews, or if they aren't expecting it now.

My guess is that the NWS mets expect the front to clear north Texas by the time significant QPF amounts are lined up across the frontal boundary. This appears to be much more a south-southeast Texas event.

As with anything else, timing is going to be critical in terms of who, if anyone, experiences significant to extreme rainfall. It could be a total bust ... could be like Oct. 94 or 98 when parts of Texas saw Biblical rainfall amounts nearing 28 inches ... or somewhere in between.

[gboudx]

Well, in another part of the AFD Johnny posted, they mentioned PWATS amounts as being:

"THE GFS SHOWS
THAT PWATS WILL RISE FROM 1.5 TO 2.25 INCHES OVER THE WEEKEND
BECAUSE OF THIS PROCESS."

Hence the call of a possible significant rain event. In fact, they went into a nice discussion and explanation of how the high level moisture from TS Lane would affect the weather. That is part of the "process" they refer to. So, I'm puzzled why this AM AFD doesn't continue the discussion of this possible significant rain event. It's no big deal, but I hope the forecast of some areas getting 2+ inches holds. Soon, many areas may enter Stage 4 drought restrictions which is the most severe.

[Portastorm]

Well, in another part of the AFD Johnny posted, they mentioned PWATS amounts as being:

"THE GFS SHOWS
THAT PWATS WILL RISE FROM 1.5 TO 2.25 INCHES OVER THE WEEKEND
BECAUSE OF THIS PROCESS."

Hence the call of a possible significant rain event. In fact, they went into a nice discussion and explanation of how the high level moisture from TS Lane would affect the weather. That is part of the "process" they refer to. So, I'm puzzled why this AM AFD doesn't continue the discussion of this possible significant rain event. It's no big deal, but I hope the forecast of some areas getting 2+ inches holds. Soon, many areas may enter Stage 4 drought restrictions which is the most severe.

Yup ... no doubt ... y'all could use rain and plenty of it!

[jasons2k]

Just keep in mind Precipitable Water values (PWATS) are not a forecast for precipitation amounts.

[Portastorm]

I think the atmosphere is already getting primed here in South Central Texas. We're getting some streamer showers along the I-35 corridor this morning ... and rain wasn't even in the forecast!

Is this low level inflow continues and is aggravated by copious amounts of Pacific moisture via Lane as well as a frontal boundary ... oh my !

As for the PWATS, Mr. Schlitz is correct. That only tells you what the atmosphere is capable of dumping on you and not necessarily what it WILL dump on you.

[jasons2k]

Yes, the moisture is streaming in faster than the models indicated and faster than forecasted. Jeff said this in his morning email and also the NWS Houston-Galveston mentioned in this AM's AFD. They have upped the chances of rain for today.

As for PWATS, just for more clarification, it is simply a measure of how much precipitable water exists in a given column of air at a given time. All-time PWATS top out in Houston around 2.8 inches, as was the case with Allison. Of course, as we saw, some locations in the area ended up with 10X that amount of actual precipitation.

In general, if PWATS are above 2 inches, it's a very moist/tropical airmass with slow-moving storms capable of producing several inches of rain.

[Johnny]

I hit a nice shower on I-45 this morning near the Woodlands. It only lasted about 3 to 4 minutes but it was a pretty good rain while it lasted. It looks pretty juicy out right now. I was gonna wait till Sunday morning to go up to our ranch in Madison County but I think I'll go in the morning to get some things done. Our property up that way is horrible when it is saturated. I've gotten stuck up there so many times it isn't even funny.

[gboudx]

Yeah, I'm aware of what PWATS means. I only quoted that part to show that the PM AFD was expecting a very moist atmosphere, capable of the significant rain even they mentioned. They did say that some areas could get 2+ inches of rain as well. Anyway, we'll see what the PM crew says today.

[TexasStooge]

I know we need some rain in the North Texas area, but the last thing anyone wants is a flood.

[Yankeegirl]

local 2 just mentioned that the front could cause some really strong storms monday into monday evening,...

[Yankeegirl]

Very nasty line of storms moving into my area from the south...it got really dark all of a sudden...and now its starting to thunder... I live 7 miles north of I-10 and Highway 6...

[jasons2k]

Yep, it's been pouring here by the Galleria