SW LA/SE TX Winter 2012-2013

[vbhoutex]

The threat continues with some rains already this morning and radar showing more building S and SW of Houston metro and moving N. Here is Jeff's morning email:

Major storm system will bring high impacts to the area today-late Wednesday.

Flash Flood Watch in effect through Wednesday evening for the entire area.

Severe weather threat will be increasing late today into tonight.

Discussion:

Powerful upper level storm system over N MX is starting to spread lift across the area with numerous showers and thunderstorms having developed in the last 1-3 hours over the southern ½ of the area. These storms appear to be the result of some sort of weak embedded disturbance in the SW flow aloft. Warm front is still located out over the Gulf waters and only slowly moving toward the coast. Strong 850mb moisture advection over the top of this front and into the cool air N of the boundary is resulting in widespread fog, drizzle, and light rain with the above mentioned stronger cells. As surface low pressure develops and deepens over SW TX today the warm front will begin to move northward, but how fast this happens will help determine the location where the greatest rainfall will occur. Areas should be warm sectored by late tonight with the main thrust of the upper level storm moving into C TX and SE TX on Wednesday. Expect a line of thunderstorms to develop over central TX into the coastal bend and spread slowly into SE TX during the day with heavy rainfall and severe weather.

Heavy Rainfall:

Already picked up 1.68 inches of rainfall this morning along the Harris/Montgomery County line including 1.0 inch in 15-minutes which suggests this air mass is very capable of some high totals in a short period of time. Given the tropical tap from the eastern Pacific in the mid and upper levels combined with a strong Gulf inflow, moisture levels will approach or exceed maximum values for early January…with PWS of 1.8-2.0 inches which is at or near summer levels. This combined with the threat for repeat cell movement…training will support the threat for very heavy rainfall possibly for an extended period of time especially near and north of the warm frontal boundary.

While models are showing the greater totals across our western and northwestern counties, the entire area is at risk and it is hard to determine at this point where the axis of heaviest rains will develop, although for today it appears areas south of I-10 have the biggest threat and then further inland tonight, but it is debatable how far inland the axis of heavy rainfall may spread. I am leaning toward the heaviest rains anchoring closer to the coast with a slower northward movement of the warm front.

With grounds already wet from recent rainfall, rainfall of this magnitude will produce significant run-off and rises on area watersheds. Some watersheds will likely exceed their banks. Additionally, the short duration intense rainfall will lead to street flooding in the urban areas.

Severe Weather:

A marginal threat for severe weather will exist today along the northward returning warm front. Feel this threat will be mainly near and offshore of the coast. A few stronger elevated storms may spread inland from the coast with a marginal hail threat. As the warm front shifts inland tonight low level wind fields will be increasing over the area and the threat for isolated tornadoes will increase. Lack of good surface instability should preclude a significant outbreak of tornadoes, but a few weak short lived tornadoes will be possible.

Greater severe threat looks to be on Wednesday as the main forcing from the upper level storm arrives into the area. Linear nature of the forcing supports a squall line type event with the main threat being wind damage. There remains some uncertainty as to how much activity will be developing in the warm sector ahead of this line and if this will keep instability on the lower side. Could see a few tornadoes in the cells across the warm sector given the favorable low level wind shear that will be in place. Damaging winds to 60mph will be possible along the advancing squall line especially within any bowing segments of the line.

Extended:

Next storm system will arrive into the area on Saturday with a strong cold front late Saturday or early Sunday. Rains will begins on Saturday and last through Monday…and while not expected to be heavy…the prolonged nature of light to moderate rains on top of what will then be very saturated grounds could lead to more run-off concerns especially since area rivers will just be reaching their peaks at this point. Highs on Saturday in the 70’s will tumble into the 40’s and 50’s on Sunday under cold air advection and rainfall.

SPC Severe Weather Outlooks:

http://www.spc.noaa.gov/products/outlook/

HPC 1-3 day rainfall Totals

[PTrackerLA]

Flash Flood watch just hoisted for my area. Looks like we are primed for a significant event. I would not be surprised to see some areas pick up over 10" of rain. This morning on my drive to work I still noticed many areas in open lots/fields of standing water. The grounds are very saturated, this could get ugly. Also just looked at 12z GFS and it has a 5"-10" QPF bomb right over Lafayette and this is just over the next 24 hours.

...FLASH FLOOD WATCH IN EFFECT THROUGH WEDNESDAY EVENING...

THE NATIONAL WEATHER SERVICE IN LAKE CHARLES HAS EXPANDED THE

* FLASH FLOOD WATCH TO INCLUDE PORTIONS OF CENTRAL LOUISIANA...
SOUTH CENTRAL LOUISIANA AND SOUTHWEST LOUISIANA...INCLUDING
THE FOLLOWING AREAS...IN CENTRAL LOUISIANA...AVOYELLES AND ST.
LANDRY. IN SOUTH CENTRAL LOUISIANA...IBERIA...LAFAYETTE...
LOWER ST. MARTIN...ST. MARY AND UPPER ST. MARTIN. IN SOUTHWEST
LOUISIANA...ACADIA AND VERMILION.

* THROUGH WEDNESDAY EVENING

* SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP AND MOVE
NORTH ACROSS SOUTHEAST TEXAS...CENTRAL AND SOUTHERN LOUISIANA.
THE HEAVIEST RAINFALL...AND THE GREATEST POTENTIAL FOR FLOODING
RAINS...WILL COME LATE TONIGHT INTO WEDNESDAY AS A SLOW MOVING
SURFACE FRONT ADVANCES THROUGH THE AREA. RAINFALL TOTALS THROUGH
LATE WEDNESDAY NIGHT ARE EXPECTED TO AVERAGE 3 TO 5 INCHES OVER
CENTRAL AND SOUTH CENTRAL LOUISIANA...AND 5 TO 7 INCHES OVER
SOUTHWESTERN LOUISIANA AND SOUTHEAST TEXAS. LOCALLY HIGHER
AMOUNTS ARE POSSIBLE.

* RECENT RAINFALL EVENTS HAVE RESULTED IN SOILS WITH A REDUCED
ABSORPTION CAPACITY...AND RAINFALL THAT OCCURS TODAY AND
TONIGHT WILL ONLY SERVE TO WORSEN THIS SITUATION IN THE LEAD
UP TO THE PERIOD OF GREATEST RISK...WEDNESDAY AND WEDNESDAY
NIGHT. URBAN FLOODING WILL BE A RISK FOR THE DURATION OF THE
EVENT GIVEN THE POTENTIAL FOR HIGH RAINFALL RATES. FLOODING OF
RIVERS AND BAYOUS MAY ALSO BECOME A CONCERN ON WEDNESDAY DUE
TO THE POTENTIAL WIDESPREAD NATURE OF THE EVENT.

[PTrackerLA]

12z GFS shows 8.19" of rain for Lafayette by Thursday afternoon

[CYCLONE MIKE]

Was just thinking this same PT. Noticed on radar a lot of rain and moisture streaming nne/ne out of gulf heading straight for s. central la. Been raining here since about 8:30 although light. Kind of surprised that flood watch has not been issued over here as well considering our grou ds are also saturated with standing water in a lot of places.

[BigB0882]

What kind of rain is it showing for Baton Rouge?

[vbhoutex]

Latest update from Jeff Lindner:

Active warm front over the Gulf of Mexico is slowly lifting toward the coastal counties early this afternoon. Surface moisture convergence is being maximized in the area from west of Corpus Christi to near Galveston and expect this to push inland about 20-30 miles during the afternoon hours as the warm front slowly moves northward. Deep convective complex that has formed near the warm from over the NW Gulf has been “robbing” best moisture inflow for the past few hours, but this complex is moving deeper into the Gulf allowing an influx of rich tropical air along the Mexican coast to surge northward to Matagorda Bay.

With the warm front impinging on the coast counties and increasing upper level divergence increasing this afternoon expect a gradual increase in thunderstorms producing heavy rainfall to fill in from Corpus to Bay City to Baytown and shift slowly northward this evening and overnight. Very heavy rainfall of 1-2 inches per hour can be expected with this activity.

While cell motions are rapid to the northeast, the cells have been showing a tendency to align and training in SW to NE bands over the region and this type of training will limit the breaks between cells reduce the amount of time for storm water to run-off and increasing the flooding threat.

Based on the latest model, RFC, and HPC rainfall forecast I see no reason to deviate from the rainfall forecast at this time with widespread 2-4 inches still likely with isolated amounts to 7 inches.

Will also need to keep an eye on any cell rotation near/along the warm front late this afternoon and evening as a few isolated tornadoes may be possible.

[cycloneye]

Plenty of rain in the region. Still loop.

[PTrackerLA]

Lafayette looks to be under the gun for the next several hours. It has gotten fairly dark outside now as well. Local weatherman just showed a model run that shows 9.30" in Lafayette and 6.70" for Baton Rouge through Friday morning. http://ow.ly/i/1ltYt

Looks like the axis of heaviest rains has definitely shifted east in the GFS and we are now the bullseye .

[cycloneye]

That is a deluge in LA. Be careful over there and stay safe.

http://oi45.tinypic.com/2ee94b8.jpg

[CYCLONE MIKE]

Lafayette looks to be under the gun for the next several hours. It has gotten fairly dark outside now as well. Local weatherman just showed a model run that shows 9.30" in Lafayette and 6.70" for Baton Rouge through Friday morning. http://ow.ly/i/1ltYt

Looks like the axis of heaviest rains has definitely shifted east in the GFS and we are now the bullseye .

One of our guys showed those models at five but said the GFS was "too hot" and didn't believe it. Has more confidence in there in house model which shows us getting about 3-3 1/2in thru Thursday and said after all said is done by Monday we could have 6+. Have to disagree with him on this. The GFS was correct with all the rain more east today, we have already had more than an inch since lunch, and there is a ton more to go before the night is over.

[CYCLONE MIKE]

That is a deluge in LA. Be careful over there and stay safe.

http://oi45.tinypic.com/2ee94b8.jpg

Thanks cycloneye. Just a nasty wet day. Most yards are under water, but its nothing we cant handle. Now if we do receive the 7-9 inches could have some bayou/ river flooding problems.

[PTrackerLA]

Just went over 3" at the house and there's not really an end in sight. The best news may be that the heaviest rain seems to be centered over the Atchafalaya basin right now which is swamp/water but we look to be socked in the moderate rain for some time now. Vermilion river in Lafayette is right now crossing into flood stage as well.

[CYCLONE MIKE]

We are at about 2.5 over here and like you said tons more coming. Guess our local guy will be eating his model come tomorrow since he said we would get upwards of 3.5 thru Thursday.

[Jagno]

Here in Lake Charles it has been very light rain intermittently this afternoon. Certainly nothing to get excited about.

[BigB0882]

The 18z GFS is forecasting an even bigger amount of rain for my neck of the woods in another 48 hours or so. This is simply the first round, then Texas gets a lot more in the next 24 hours and then it comes back and Louisiana is absolutely deluged after another 30 hours or so. It must be showing another 4-6 inches for SC and SE LA in that 2nd round.

[CajunMama]

Just went over 3" at the house and there's not really an end in sight. The best news may be that the heaviest rain seems to be centered over the Atchafalaya basin right now which is swamp/water but we look to be socked in the moderate rain for some time now. Vermilion river in Lafayette is right now crossing into flood stage as well.

Rob Perillo was saying the Vermilion is flowing north. That's not good. Not good at all.

[vbhoutex]

Rains/storms moving in here in Houston again. Nothing like your amounts yet, but they are telling us tomorrow will be a deluge and with what I see in the GOM and to our SW I will not be at all surprised with 3"-5" here. The low that is helping cause all of this hasn't even moved out of N Mexico yet.

[JSDS]

My rainfall total from 6:00 pm yesterday to 6:50 am this morning was 5.5". I am just a stone's throw from Baton Rouge, on the east side. I hate to see the storm total when it's all said and done, because everything is beyond saturated and the rain is still coming down.

[vbhoutex]

Latest from Jeff Lindner:

Heavy rainfall event underway over the coastal bend into C TX and will spread into SE TX over the next 4-6 hours.

Slow moving upper level low located over N MX is spreading increasingly strong lift across coastal TX and a rapid increase in banded heavy rainfall has occurred from near Austin to Victoria to near/east of Corpus Christi. Cloud tops are cooling in this region and this supports the activity forming into more solid bands/lines of heavy rainfall. An extremely favorable flow from south to north off the western Gulf of Mexico will continue to feed this axis of heavy rainfall as it progresses slowly toward the east. Rainfall rates of 1-2 inches per hour with totals of 3-4 inches in 3-4 hours will be possible with this band. Due to already saturated grounds, run-off will be increased and street flooding will be possible.

Short term meso scale models are in good agreement with this band slowly moving across the area from now to mid to late afternoon. There will be a slight severe weather threat associated with the activity today, but thus far limited instability has resulted in no storms reaching severe levels and the threat is fairly small for today.

By late this evening the upper level low should be progressing into C TX with a large mass of dry air over MX surging into the area ending rain chances.

Extended:

A couple of dry days on Thursday and Friday will be followed by increasing chances of rainfall late Saturday into early next week as a strong cold front arrives in the area late Saturday night and early Sunday. Front will stall over the NW Gulf with cloudy and wet conditions developing in the cold post frontal air mass. Current thinking is that most of this rainfall will be on the light to moderate side with fairly low amounts over an extended period of time, but this appears to be a possibility of some heavier rainfall on Sunday. Temperatures will cool significantly behind the front with lows in the 30’s and highs in the 40’s/50’s.

I only had 0.34" of rain yesterday in my neighborhood. I do know other areas of metro Houston got up to 2". Like I friends in LA we are saturated too. Not liking what I am seeing on radar as what is there is still to our West, but will be moving E to NE today.

[PTrackerLA]

Storm total form yesterday/overnight at 3.6" at my house. The river here is almost 2 ft above flood stage so will be closely watching how the next round of rains set up today.