It’s been over a month now since I’ve filmed any tornadoes. There have been chases, there have been cool photography, but no major tornado events since April 14. There are indications that severe weather may return to portions of the Plains by the weekend and next week, but that’s just speculation at this point. I’ve been using this downtime to catch up on some other hobbies and finally have time to add several items to the Texas Storm Chasers website. I’ll go ahead and put them in bullet style.

* May 6 and May 11 photography posts added to the “Latest Chases” box on the homepage.

* Chase logs for February 28, March 18, and March 21 have been added and are available by accessing the Storm Chase Logs tab in the linkbar.

My next goal is to add my chase log for April 3. That may sound simple enough, but I’m going to spend extra time writing out every single detail of that chase. I’m going to try and do that today and I have no doubt it’s going to end up being a short novel. There are a few items I’m going to address in that (driving on highway shoulders in grid-locked traffic, the overall mindset of the day once it became apparent that was happening, and a secret I haven’t revealed about April 3.) The 28 second video we uploaded to our YouTube channel was from my new camera. What folks don’t know is that I had a HD camcorder running on the dash. I’ll reveal some of that video in the April 3 chase log as well. I’ve chased many setups over the years and up until April 3, the scariest day for me was my near death experience on April 24, 2010 out in Mississippi. That changed on April 3, not because of danger to my personal self, but the overall situation.

I’ll detail all of that in my April 3rd log.

~ David

5/11/2012 – Red Oak, Texas Sub-Severe Thunderstorm

This day wasn’t supposed to be a chase day, but when a severe thunderstorm developed unexpectedly about thirty minutes to his northwest, David Reimer couldn’t resist the opportunity to get some storm photography. By the time the storms reached David, they were well below severe limits, but still provided a photography opportunity just minutes from his house.

5/06/2012 – Jacksboro, Texas Supercell/Bow Echo

Texas Storm Chasers’ David Reimer and Jenny Brown spent the afternoon taking photos of pop-up thunderstorms along with Bellevue, Texas before a cell finally took hold and became severe just before sunset in Jack County, Texas. The duo intercepted the severe storm in Perrin, TX where they observed power flashes, tree damage, and measured a 54 MPH wind gust.

Here is the latest severe weather outlook issued for the evening/overnight hours from the Storm Prediction Center. The standard severe weather risk is defined by the yellow color with the enhanced zone defined by the red. There is a low severe weather threat in the brown shaded zone.

Brown Shaded Zone: Low severe weather chance (5% chance of severe weather occurring within 25 miles of your location tonight.)

Yellow Shaded Zone: Standard severe weather chance (15% chance of severe weather occurring within 25 miles of your location tonight.)

Red Shaded Zone: Elevated severe weather chance (30% chance of severe weather occurring within 25 miles of your location tonight.) This is where the highest tornado potential is also located.

A Tornado Watch has been posted for much of South Central Texas until 3 AM. The highest tornado threat should remain along and south of Interstate 10, but severe weather is possible across all of the watch.

In addition, a Flash Flood Watch is in effect for much of the Texas Hill Country and South Texas. It is my belief that flooding will become the biggest issue overnight. We’ll post updates as warranted on our Facebook and Twitter pages, along with our blog.

Radar at 1:41 PM

At the time of this posting, several tornadic supercells were in progress in Deep South Texas. Multiple brief tornadoes have been confirmed at this time, but damage surveys will be conducted after the event to confirm the exact number and magnitude of tornadoes. This event is on-going and will continue through the afternoon and evening hours.

Chance of severe weather within 25 miles of your location

This is the latest severe weather outlook showing the probability (chance) of experiencing severe weather within 25 miles of your location this afternoon and this evening.

Brown Shading: “Low” chance of severe weather (5 percent chance of having severe weather occur within 25 miles of your location.)

Yellow Shading: Standard Risk of severe weather (15 percent chance of having severe weather occur within 25 miles of your location.)

Red Shading: Elevated chance of severe weather (30 percent chance of having severe weather occur within 25 miles of your location.)

Primary Hazards: Tornadoes (mainly in the elevated risk) and Tennis Ball Size Hail with the strongest storms

Secondary Hazards: Straight-line winds and Flash Flooding (risk of Flooding will increase tonight)

Chance of severe weather occurring within 25 miles of your location on May 10, 2012

This graphic shows the chance of severe weather occurring within 25 miles of your location today and tonight. The Storm Prediction Center has issued a standard “slight” risk of severe weather, shown by the yellow shading, for areas along and south of Interstate 10 from Fort Stockton eastward to San Antonio, then southeast to El Campo, Texas. Within this yellow shaded zone, there is a 15 percent chance of experiencing severe weather within 25 miles of your location. In the brown shaded zone, there is a low chance of severe weather, meaning a 5 percent chance of experiencing severe weather within 25 miles of your location.

Brown Shaded Zone: “Low” chance of severe weather (5 percent chance of severe weather occurring within 25 miles of your location.)

Yellow Shaded Zone: Standard Risk of severe weather (15 percent chance of severe weather occurring within 25 miles of your location.)

Primary Hazards with the strongest storms: Golfball size hail and damaging straight-line winds over 60 MPH

Second Hazards with the strongest storms: Brief tornadoes

The risk of Flooding will increase later this evening with a Flash Flood Watch already posted for much of South Texas.

This is the latest five day rainfall accumulation forecast released moments ago by the Hydrometerlogical Prediction Center. This graphic shows anticipated rain totals from 7 PM this evening through 7 PM on Monday. Notice how much of the state, with the sad exception of the Texas Panhandle, looks to receive at least half an inch of rain over the coming days. The heaviest rain totals are expected to be located from the Texas Hill Country and points south and east. In fact, we may be dealing with flash flooding in some areas by the weekend as tributaries become filled. We’ll keep an eye on that possibility, but overall it looks like we’re in for a multi-inch rain event!

The cap is a region of warmer air over a layer of cooler air that keeps a lid on convective lifting and can inhibit thunderstorm development.   Remember from Thunderstorm 101, warm air from the earth’s surface wants to rise and will continue to rise as long as it’s warmer than its surroundings. Thus, when it reaches a layer of air equal to or greater than it’s temperature at that height, it will no longer rise.  Convection, or cloud formation, is then thwarted and unable to develop any further without the aid of other lifting mechanisms such as an approaching frontal boundary or surface heating that exceeds that of the cap.

What causes caps to form?  There’s quite a few, but the loss of daytime heating from the earth’s surface is one primary cause.  The earth’s surface cools faster than the air above, so you will have warmer air aloft most nights and mornings.  Once the sun has a chance to heat the earth’s surface, that heat is reflected back up into the atmosphere heating it as well.  As a result, the cap is typically strongest during the night and early part of the day, and weakest in the afternoon during peak daytime heating.  That’s when it’s most likely that the cap will break and enable storms to form if there is enough moisture and instability in the atmosphere.   Another primary cause is warmer mid-level air masses moving over the cooler ground level air masses.  Winds can move across us from different directions at different levels in the atmosphere, and one prevailing wind we have in Texas each summer at the mid-levels is a southwest or westerly wind which brings in that warmer layer of air from the arid regions of Mexico and our southwestern states.

A cap is considered “weak” or “breakable” when there is only a small temperature increase between the air aloft and the air at ground level.  Conversely, a cap is strong when there is a large temperature increase in the air aloft over the air at ground level.  The cap can be the difference between quiet weather and a severe weather.  If the cap HOLDS, it will be a quiet weather day.  However, if the cap weakens or BREAKS, daytime convection could explode and produce damaging thunderstorms.

The Storm Prediction Center has placed a large section of the Big Bend County, the Texas Hill Country, and parts of East Texas in a standard risk of severe weather for the afternoon and evening hours.

Brown Shaded Zone means there is a “low” chance of severe weather – 5% chance of severe weather occuring within 25 miles of your location.

Yellow Shaded Zone is the “standard” severe weather risk – 15% chance of severe weather occuring within 25 miles of your location.

Red Shaded Zone is an “elevated” risk of severe weather – 30% chance of severe weather occurring within 25 miles of your location.

For weather information for your specific location, please visit your local National Weather Service office at www.weather.gov