Thursday, October 18, 2007

Special Severe Weather Update

5:35 p.m.

The cap looks like it is quickly breaking. Our weathercaster Lee Ann Okuly has arrived and reported a few large drops of rain. All the storm spotters are out in the field and all eyes are on Live Doppler 18. We will keep you updated. Right now it looks like our time frame of 6 p.m. to 10 p.m. is on track.

3:45 p.m. Thursday

Here is the main threat breakdown for our entire state. Notice the two orange-shaded areas have the highest tornado risk. The yellow areas could still see isolated tornadoes with a higher risk of damaging wind and large hail. Now it is time to just wait and see when and where the thunderstorms fire up. I still expect a tornado watch by time our news begins. I will keep you posted.

2:30 p.m. Thursday

Here is a brief re-cap of the conference call with the National Weather Service in Indianapolis:

The main threat at this time for Lafayette continues to be straight-line wind damage with wind gusts of 60 to 80 mph. Tornadoes cannot be ruled out with the highest threat of tornadoes occurring late this afternoon through 8 p.m. tonight. If storms pop early in our area we will have to really be on guard for not only wind damage but tornadoes. Although, a bit of good news for our viewing area is that the highest tornado risk in Indiana at this time will be far northern Indiana from Lake County through South Bend....a second high risk tornado area is setting up from southwest Indiana to Indianapolis and east to Richmond.

The time-frame still looks like the storms will roll through our area between 6 p.m and The 10 p.m. and it is still a fairly broad range because there are discrepancies on the actual timing of the storms on the models. It all depends on when the cloud field in Illinois fires up into thunderstorms. That can be very tricky to forecast.

The storms will be quick-movers with some cells moving at 50 mph to the northeast.

A tornado watch will likely be issued for our viewing area just before our newscasts tonight.

The latest from the Storm Prediction Center:

The wind damage threat has increased to 45 percent late this afternoon and evening. The tornado and hail threat remains the same.

11:30 a.m. Thursday

Here is the latest from the Storm Prediction Center for the Lafayette viewing area (within 25 miles of your backyards):

Chance of Straight-line wind damage: 30%
Chance of Tornadoes:15%
Chance of Large Hail: 15%

The latest discussion seems to favor straight-line winds here in our viewing area with higher risks of tornadoes the farther south you go especially from southern Indiana, Kentucky, and Tennessee. There will be an upper-level disturbance moving through these areas which would intensify their developing thunderstorms by late today and overnight. Here at home, the storms look like they will take their time initiating and this could lower our chances of seeing any tornadoes as we lose the daytime heating. The latest model runs keep pushing back the timing of when our thunderstorms will develop. The later they form the better. Also, the big supercells that will likely form to our south will limit northward transport of moisture and high dewpoints. This could help limit our thunderstorm development.

10:00 a.m. Thursday:

The sun has popped out here on the southside of Lafayette. This is not what you like to see before a possible severe weather outbreak. The sun adds to the instability of the atmosphere. It is the equivalent of adding high octane fuel to the atmosphere. There already is incredibly high wind shear developing in the atmosphere. This tends to add spin to thunderstorms. But in meteorology we know that you have to have just the right mix of shear and instability. The shear could become so strong that it could literally rip off thunderstorm tops as they form by late today and tonight. This would favor squall-line of thunderstorms here at home to develop with the main threats being straight-line wind and large hail. Tornadoes would still be possible though even in this situation, but much more isolated in nature. We will continue to see how this plays out. Here are a couple of the latest updates available below. There will be a conference call at 2 p.m. that I will share with you later here on the blog. Right now I still do not see anything developing until we get closer to 7 p.m. But this could still change so stay tuned.

Here was the early morning statement from the National Weather Service in Indianapolis:

There is a major risk of severe thunderstorms today and tonight. The main threats from these storms will be tornadoes and damaging straight-line winds. Severe weather is most likely between 5 p.m. and midnight.


Anonymous said...

Thank you for keeping us informed with a timeline. I am glad the TSC kids are already home from school today.

Anonymous said...

I echo the other comment made here. I'm watching this like a hawk. Not sure if I want it before dark or after, but guess we will take what we get. I better not hear those words " WE HAD NO WARNING" cuz you have been on top of this for days!
Mary Anne