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A Dual Pol Radar Tutorial: The Vilonia, Arkansas Tornado

Posted on Friday, May 2, 2014 at 3:30 PM MST

Dual polarization radar is an incredibly powerful tool for tracking severe weather. One important use for dual-pol radar is to track strong tornadoes by detecting the debris field with the radar. Similar to the Moore tornado last year, the April 27, 2014 Vilonia, Arkansas tornado passed about 10 miles north and west the radar site, providing about as good a low-level scan of the tornado as possible.

First, let's recall what a classic supercell looks like on radar. The area of greatest interest is the hook echo and tornado, located near the back of the storm. Remember that when a tornado picks up debris and throws it in the air, it has a high reflectivity (the radar beam bounces off of it very easily), and shows up in the scan below as purple and pink. The scan is from last year's Moore tornado.

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Posted In: Education

Tagged: Radar, Dual Pol, Velocity, Tornado, Hail, Rain, Debris


Storm Season Tries to Get Going in Oklahoma

Posted on Thursday, April 3, 2014 at 1:10 PM MST

The storm chasing season tried very hard to get started yesterday, but it just wasn't meant to be. All of the ingredients were in place, but a deck of cirrus clouds (which limited instability by keeping surface temperatures down), strong cap and weak forcing on the warm front and dryline boundaries prevented any storms from forming until sunset.

It was a tough decision not to chase, but in the end, driving for 2-3 hours only to chase for at most 45 minutes and then have to drive the same 2-3 hours home just wasn't worth it. When it was all said and done, quite a few hail-producing storms went up in Kansas, but all the action was after sunset. We'll give it another shot next time.

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Posted In: Chase Recaps

Tagged: Hail, Bust


Okla. Thundersleet Part 2: How The Thunderstorms Formed

Posted on Wednesday, March 12, 2014 at 10:00 AM MST

It takes a unique weather setup to generate thundersleet and thundersnow. It takes an even more unique weather setup to generate thunderstorms with surface temperatures of only 12°F. In order to understand these setups, we need to make sense of the concept of an elevated or high base thunderstorm. These can include any type of thunderstorm, from your wimpy little garden variety thunderstorm to powerful supercells.

In the typical surface-based thunderstorm, warm, moist air is lifted from the surface or ground-level into the updraft of the thunderstorm. The cloud base of surface-based thunderstorms is typically only a few hundred feet above the ground. However, if we pass a powerful cold front through the area, such as we did right before the thundersleet, we create a very stable layer at and just above the ground level. In this case, that stable layer was only about 3500 feet deep, but that's still plenty deep to prevent parcels from being lifted from the surface into the updraft. If we lift a parcel from the bottom of the unstable layer (just above 3500 feet), there is sufficient instability to form thunderstorms. The base of the thunderstorm will be a few hundred feet above the bottom of the unstable layer, which in this case would be around 3700 or 3800 feet above the ground (just under 5000 feet above sea level), hence the term high base thunderstorm (or elevated thunderstorm). This phenomenon can be showed very well in the Norman soundings from March 2nd.

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Posted In: Education

Tagged: Thunderstorm, Sleet, Snow


Oklahoma Thundersleet Part 1: Video and Observations

Posted on Tuesday, March 4, 2014 at 4:00 PM MST

One of the most spectacular displays of thundersnow and thundersleet I've ever seen occurred just south of the Oklahoma City metro this past Sunday. A pretty unique weather setup presented itself as a winter storm passed over the area, creating favorable conditions for thunderstorms despite surface temperatures around 12°F. A band of convection set up across southern Cleveland, McClain, and Pottawatomie Counties in the morning, training over the same area before beginning to slide north in the early afternoon. Around 1:30 PM, these thunderstorms began to approach the Norman area. You can check it all out in the video.

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Posted In: Education

Tagged: Thunderstorm, Sleet, Snow


Beautiful and Impressive Storm Coming Ashore in California

Posted on Friday, February 28, 2014 at 10:15 AM MST /9:15 AM PST/

Cloudy with a change of cinnabons? No, Jim Gaffigan is not coming to your neighborhood. Nor will tasty baked goods be falling from the sky (how awesome would that be though). Instead, one of the most impressively beautiful and textbook upper-level mid-latitude storm systems in recent years is currently coming ashore in California. The structure of this storm system is so perfect it looks like a cinnabon on the satellite image. The storm is big enough to bring rain to the entire west coast, but the most rain will fall in the drought-striken areas that need it most.

GOES Satellite Image - Friday at 6:30 AM CST/4:30 AM PST

Storm Brings Much-Needed Rain to Drought-Stricken California

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Posted In: Forecasts

Tagged: Winter Storm, Mountain Weather, Rain, Drought


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