Tuesday, April 10, 2012

Most Concern Resides Over Saturday Severe Threat

The most concern for severe weather is residing in the 'Day 5' area shaded in purple, as it has been forecasted by the Storm Prediction Center the longest.

The latest GFS has a sizable amount of instability forecast for the area covered in Day 5, amounting to up to 2000 j/kg, considered substantial for severe storms. In addition, wind shearing from the surface to mid levels will be fairly high, at 60 knots, enhancing the potential for tornadoes.

Here is the set up for Day 5. A dry line will be in place over western Texas, meaning a significant dew point difference will be present in that area. A warm from extending north will be pulling warm, moist air northward and enhance instability.

I don't have much time, so this is all I can give you, but I do consistently update my Facebook Page at www.facebook.com/TheWeatherCentre

9 comments:

Anonymous said...

Wait, wait, wait. Last year I thought that you said that 2000 was the least needed for severe thunderstorms, and now your saying that 2000 is substantial.

ERN WX said...

I have seen severe thunderstorms develop in cape levels of only 250 j/kg. It is not ideal but it can happen. If I want severe thunderstorms I want cape values in the 1500+ range. Once things get over 3500 j/kg conditions can become very dangerous.

ERN WX said...

Please note the higher the values the higher the severe weather threat. But convective available potential energy is not the only factor when it comes to severe weather. To name a few you also need strong wind shear, steep lapse rates, and moist air.

Andrew said...

Anonymous: Last year, that was the guideline I strictly abided by. However, after seeing the wild year of weather last year and this year, it has come to my attention that 2000 is actually pretty substantial for thunderstorms.

Eastern WX: Your last comment is absolutely correct.

Anonymous said...

Actually ERN WX's last comment isn't correct. In general yes but once things get above 3500 j/kg you also need a substantial amount of shear. Otherwise, you get a situation with random pulse thunderstorms that destroy themselves if they get too strong. If you can get shear though, high instability like that usually leads to damaging winds/hail, not really tornadoes unless the shear gets crazy (100 kts+)

ERN WX said...

Anonymous, I clearly understand you need strong wind shear in excess of 40 knots to keep supercells alive. I have seen tornadoes develop in an environment where there is very little shear. All of the shear in the world won't help if you have no cape. I said, "... you also need strong wind shear..." I have been doing meteorology for several years now.

MTG said...

Not wanting to be rude, but it is rare for shear to exceed 100 knots. I am a co-worker with ERN WX.

MTG said...

All of the cape, shear, and moisture in the world will go nowhere without a trigger. IE cold front or dry line.

Andrew said...

Anonymous: ERN WX's comment was indeed correct.

MTG: Welcome! Yes, shearing must be very high for the strongest tornadoes. I believe April 27, 2011 tornado outbreak had a 140 mph jet stream, if I remember correctly.