Sunday, February 8, 2009

Caught in the Middle

We're back to weather for today. This time not about winter storms, but instead spring storms in the winter.

It appears that we might have two rounds of thunderstorms this coming week. The first round will come Monday. These shouldn't be too bad. The second round will come Tuesday evening and last through the first half of Wednesday.

The Storm Prediction Center, the meteorologists that issue Severe Thunderstorm/Tornado Watches, have put the area in a "Slight Risk" of severe weather for Tuesday evening. (See image below. You can click on the image to see a larger version.)

Looking at SPC's probabilities of severe weather leads me to believe that we could see an upgrade to a moderate risk for parts of Arkansas. (See the image below.)

When you see the probabilities from the SPC, it does not mean that there is a 30% chance of severe weather. It means that there is a 30% chance of having one or more severe events occurring within 25 miles of any point inside of the area.

Right now it looks as though storms will fire up across eastern Oklahoma, eastern Texas, and western Arkansas. They would then move to the east. They wouldn't arrive in to southeast Missouri until later Tuesday evening if not early Wednesday morning (overnight). Most likely the storms would form in to a line with the main threat being damaging winds.

Normally you would think that would be the end of the storms. That won't be the case this time. There is still a upper level low pressure that will be slowly moving to the east. It will continue to send waves (or as I sometimes call it "chunks") of energy our way. Take a look at the upper-level wind graphic below. It might be a little confusing at first, but I will describe what you are seeing.

This is a view of winds at 500mb or approximately 18,000 feet. You are seeing lots of colors on the map. The colors represent the wind speed. For instance, the brighter yellow areas represent winds 65 knots to 70 knots or 75 mph to 80 mph.

Notice the reds and even purple out over southern New Mexico/western Texas. Just to the north of those strong winds is the upper-level low pressure center. When looking at upper-level charts you can see the waves of energy spitting out of the storm. Typically, you will see storms develop on the leading edge of the upper-level winds. The map above is for 6pm CT Tuesday.

Now take a look at the chart below which is for 12pm CT Wednesday.

See how the winds start to swing around the area of low pressure? By the way, the strongest winds at this point are right over the top of southeast Missouri, southern Illinois, western Kentucky, and northwest Tennessee. The storms that come through early Wednesday morning will have some upper-level support to keep going, but there won't be as much energy/juice (from heating and moisture) to work with. So when the storms come through here, they should be weakening. Think about it as a marathon runner runs their race, towards the end they can keep going, but they don't have as much in the tank to go as hard as they could towards the beginning.

Since the winds are right over the top of the Heartland around noon Wednesday, the next round of afternoon thunderstorms should develop just to the east of the viewing area. The SPC concurs with that thinking. Take a look at their Day 4 outlook. (The SPC does not issue slight, moderate, or high risk outlooks beyond Day 3.)

We will have to see how this pans out as it is still a couple of days away. But right now, it appears southeast Missouri, southern Illinois, western Kentucky, and northwest Tennessee are Caught in the Middle. Which can be a good thing in these situations. That being said, it does not mean that we will not see some watches/warnings out of this, but it does not look to be as bad as it could.

This is still a couple days away. We will have to keep monitoring the situation and see if things shift east or west a little.

By the way, this shouldn't be the first you are hearing about this as I have been talking about the chance of seeing some strong "spring-like" storms around the area since Wednesday.

1 comment:

Melzie said...

Well its bound to happen I saw miles of geese heading north after church today :) Keep us updated! melzie