5/21 - 11:55pm MDT - Nice LP Supercell Today

Today didn't turn out to be the best chase, but we made the best of it with the sighting of a nice low-precipitation (LP) supercell near Grande, New Mexico. This formed within a line of discrete storm cells that stretched from Southeast Colorado to Central New Mexico. The formation of these cells in a line among an environment characterized by northwest wind flow at 18,000 feet (500 mb) didn't make for the best conditions for severe storms, but a few of them did reach severe limits. Besides this low-profile supercell and possibly a couple others in the same line, an "out of the blue" classic supercell formed ahead of an eastward-advancing MCS (mesoscale convective system - line of storms) just west of Amarillo before being ingested by the actual MCS. It didn't form in the expected environment for this, so we were not in position to see this short-lived storm. More photos of the LP supercell we saw today are available on my Flickr and Facebook albums.

Our tentative plan for tomorrow is to head to the Valentine, Nebraska area to intercept a severe weather threat that may manifest up there as a large-scale trough begins affecting the Northern Plains. Many would consider this an "secondary" target area since higher dew points and better surface winds will be in North Dakota, but in this case the moisture up in North Dakota will likely be confined to an area closer to the surface since there will not be enough time for ample deep moisture to make it up that far north. Northern Nebraska should have some deeper moisture than North Dakota and even though less helicity (spinning motion in atmosphere) will be present in Nebraska, Energy Helicity Index values are still forecast to be elevated according to the Rapid Refresh model. We'll make a final determination based on data coming in tomorrow morning before heading out!

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5/14 - 12:30am CDT - Great Lightning Tonight in West Texas!

We were treated to a great lightning show just north of Pecos, Texas earlier this evening as a few isolated storms merged together to create a fast-moving line of storms (MCS) that quickly caught up with us. These storms packed some very large hail and high winds at their peak, but luckily we were able to stay ahead of them during that time. The storm kicked up quite a bit of dust in the gust front, so it created low visibilities and an eerie scene in Pecos as it moved through. This comes after a day of fruitless chasing because storms that were expected to form near the Midland, Texas area did not due to a lack of required surface heating. More photos of this storm are available on my Flickr and Facebook albums.

Tomorrow we'll likely be chasing in West Texas again, but this time it may be closer to the Mexican border. Fast winds aloft, moisture at the surface, and winds blowing up the mountains in Mexico from the east should trigger some storms tomorrow afternoon after the ones tonight move through. The setup will be relatively similar to today, but hopefully we're able to get some more stronger isolated storms out of this. Here's some of the high points from the Storm Prediction Center's discussion on tomorrow with their Slight Risk area:

IN THESE AREAS...STEEP LAPSE RATES/MODERATE DESTABILIZATION ANDVEERING WIND PROFILES WILL BE SUPPORTIVE OF SUPERCELLS WITH LARGE HAIL AS THE PRIMARY HAZARD...ESPECIALLY MONDAY AFTERNOON/EARLY EVENING. STORMS MAY AGAIN CONGEAL/ORGANIZE INTO ONE OR MORE SOUTHEASTWARD-MOVING LINEAR CLUSTERS WITH A DAMAGING WIND/HAIL THREAT CONTINUING MONDAY EVENING/NIGHT ACROSS THE RIO GRANDE RIVER VICINITY.

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6/27 - 11:15am - More Severe Weather for KY and IN

Had enough storms already? We have one more round to go before we clear things out for a while around Kentucky and Indiana. A few non-severe storms have already moved through the Louisville area this morning and the storms that are still well off to the west are weakening and beginning to take a more southerly turn.


The bit of clearing we'll see this afternoon after this morning's storms pass off to the east should help to destabilize the atmosphere in preparation for development of severe storms this afternoon. If this clearing doesn't materialize and we stay more cloudy than sunny across the area, the severe threat will be much lower. These storms should fire up in the mid afternoon across southwest Indiana and Western Kentucky and impact the Louisville area this evening. While most of these will be your run-of-the-mill severe storms with 60mph winds and hail, a few could have supercell structures or bowing segments. The embedded or isolated supercell structures will be powered by the small amount of wind shear (changing wind direction and speed with height - see 5pm NAM model output left) and helicity (turning in the atmosphere) we'll have in the area as storms form. This means a couple isolated tornadoes are possible.

The bowing segments could produce wind damage as a cold pool of air collects behind some of the more linear storms. These storms will likely last well into the evening and overnight hours and be out of the Louisville area by mid morning tomorrow or earlier. Since there is the risk for wind damage and an isolated tornado or two, the Storm Prediction Center has issued a Slight Risk area for most of Kentucky, Southern Indiana, and portions of Middle Tennessee. A 5% tornado risk exists from Chicago and St. Louis to along the Ohio River, while a 2% risk extends further southward.

6/25 - 2:45pm - Tomorrow's Entertainment: An MCS

An MCS or Mesoscale Convective System is scheduled to move through Kentucky and Indiana tomorrow morning. An MCS is basically a large cluster of storms that normally has a distinct wind-driven line of strong to severe storms on the east side as it pushes along at a decent speed. Tornadoes can sometimes form in little notches or "eddies" that develop in the strong line of storms on the east or leading side of the MCS. Given that there will be some helicity (turning in the atmosphere) from Indianapolis to Bowling Green, KY as the MCS moves through, it would not surprise me to see a Tornado Warning or two issued since there could be a little rotation aloft. This will not be a tornado event though and I expect the probability of tornadoes to remain low. This will not be an event like Wednesday when we had five tornado touchdowns in the area because we will not have supercells developing. The Louisville area can expect storms to start sometime around 7am and possibly last into the mid afternoon hours. While the initial line of storms in the morning could be strong or severe, heating during the day could intensify storms by around noon. The main threats from this complex of storms will be damaging winds (especially in the morning) and hail. The 12z NAM model run (top left) seems to have a good handle on the storms.

These storms will be driven by a mid-level shortwave trough, which is basically just a ripple or wave in the atmosphere, and a warm front rising northward. Once this warm front passes to our north tomorrow, we can expect temperatures to exceed 90 degrees again next week.

We're under a Slight Risk tomorrow from the Storm Prediction Center (left) and on the very southern edge of another one on Monday (right) since another line of storms may try to come through early in the day:

Be sure to scroll down and read my exhaustive post on the Louisville tornadoes that happened on Wednesday.

6/18 - 1:30am - More Storms Today in KY and IN, Some Severe

Storms are already forming very early this morning over Illinois near a stationary warm front and are forecast to move southeastward across Indiana and Kentucky later this morning and into the afternoon hours. Storms that pass through the Louisville area before lunchtime will have the potential to cause wind damage as they begin to feed off of some morning heating. This initial round of storms may stay to the west of Louisville and Lexington and instead focus more on the Evansville, IN area if the latest short-range models are correct. These precipitation outputs below are very general and rarely depict a perfectly precise forecast for where storms will set up, so take these with a big grain of salt:

NAM, RUC, and WRF precipitation forecasts for 11, 8, and 11am respectively

Computer models are also showing a blossoming of these storms in Kentucky and maybe some new ones in the afternoon as we add on more daytime heating. With wind shear coming into play (which is something that these storms today near the Ohio River didn't have to work with), we could be looking at an increased risk for severe weather both in the morning and afternoon hours. Since these storms will be linear and/or bunched together, tornadoes and severe hail should stay out of the picture for the most part. Wind will be the main threat with these storms, so you may want to secure that garbage can or any patio furniture that you may have sitting loose outside before tomorrow mid-morning if you live in Southern Indiana or Kentucky. Given the wind risk from these storms tomorrow, the Storm Prediction Center has placed most of Kentucky and Southern Indiana under a 30% Slight Risk for severe weather. Tennessee, save for extreme northeastern portions, should outside of the severe weather threat tomorrow. I'll be up bright and early tomorrow, so be sure to follow me on Twitter or Facebook for the latest updates as these storms approach the Ohio River!

A similar situation could unfold again tomorrow with severe weather (a Slight Risk has already been issued), but this time wind shear might be a bit more favorable for stronger storms that are more organized. The main risk again will be wind damage and possibly small hail from some of the stronger storms. Seems like late Spring is keeping things busy around the Lower Ohio Valley!

6/8 - 2:30pm - Storms Coming to Louisville

A MCS (mesoscale convective system - a line of storms) is headed for Louisville this evening from Illinois. There are no severe weather warnings associated with this line of storms, but I think heavy rain will be the biggest issue as it comes through after midnight. The Storm Prediction Center has placed areas just north and west of Louisville under a Slight Risk for severe weather today in light of the MCS making its way through.

More storms are possible tomorrow afternoon as a cold front nears the Ohio River. We're under another Slight Risk for severe storms tomorrow, but my thinking is that Southern Kentucky will be under the greatest threat as instability increases tomorrow ahead of the southeastward advancing cold front. Heavy rain will again be the biggest risk around here tomorrow as precipitable water numbers will be quite high across the region. We could easily end up with nearly an inch of rain or more by Friday here in Louisville according to the HPC's QPF outlook. Extreme amounts of four inches or more are possible south of St. Louis.

5/16 - 10:30am CDT - SE New Mexico

We're on our way to the southeast corner of New Mexico to see what kind of storms develop down there this afternoon. We're not terribly optimistic about today's setup because of weak surface winds and an ongoing MCS (mesoscale convective system - line of storms) this morning on the Texas/Mexico border. Redeeming qualities of today's setup are good instability, decent shear, and ample moisture. The increased elevation should provide a little bit of lift out there, but we're not seeing the push of dry air from the west that we need. In any case, we'll see how it goes today.

We'll be streaming LIVE video at http://stormchasertv.com if storms form today. You can follow me on Twitter and Facebook as well to get the latest updates on our chase and video streaming.

8/1 - 3:30pm - Severe Chances Looming?

The SPC has issued a SLIGHT risk for severe storms in our area later today.



While nothing is showing up near us on radar at the moment, a line of storms is starting to materialize in Northern Indiana. The SPC warns that an MCS (line of storms) could reach the Ohio River later tonight. Since this is mainly a wind event, I think we're out of the line fire for tornado problems. Even though we're under the SLIGHT risk, we might not even see any storms today. We've yet to see a tangible line of severe storms form, and the one that's forecast to form could pop up in a variety of places around the region. We'll see what happens later tonight.

7/28 - 10:30am - Wow, Rain!

I saw the weakening complex of storms south of Chicago last night before bed. It just didn't look like they'd stay together long enough to make rain down here. But they did! We've had nearly three quarters of an inch of rain this morning at my house, with just a stray shower left in the area now.

We're done with rain for today, save for some small stray showers around the area. The GFS is creating odd issues for tomorrow morning. It wants to bring an MCS (line of storms) through and then clear it out for the afternoon. There's really no other model wanting to do this, so I think the GFS is having difficulties with this pattern. Its interesting how "insistent," as the local NWS office put it, the GFS is being on this. We'll see, but I don't think we'll get an MCS tomorrow morning. At any rate, temperatures will be in the mid 90's tomorrow with heat index values in the 100's.

On Wednesday into Thursday, the remnants of Hurricane Dolly will make some rain around the area. So much for my dry weather discussion yesterday! With the rain this morning and later this week, I think we'll actually be close to normal for July precipitation.

Finally this morning, I've launched a new interactive radar page on my website. Not only does it have the interactive radar, but it also has links to local and regional radars, as well as infrared satellite. Click here or click the "Interactive Radar" button on my website to go to the page.

7/20 - 1pm - SLIGHT Risks

We're on the edge of a SLIGHT risk for severe storms from the SPC today and in the middle of one tomorrow. The radar shows some storm activity in Southern Indiana that's making its way toward us, so we should see some rain by mid-afternoon at the latest. Other storms could pop up as well, but so far nothing looks severe.

Tomorrow still looks pretty active with that SLIGHT risk. We had a joke going when I was storm chasing that a SLIGHT risk day was always worse than a HIGH risk day... which turned out to be true on two occasions on that trip. Anyway, we should see an MCS line of thunderstorms roll through here tomorrow afternoon or evening with gusty winds and heavy rain. There's a possibility that we could see some smaller, more broken storms as well, but I'm not real keen on it. I think we're going to see what we've been seeing all summer: a couple weak cells in front of a semi-strong MCS (Mesoscale Convective System - a line of storms).

6/25 - 2:30pm - Watch Out This Weekend

Here's the latest severe outlook from the SPC:



(Day 4 is Saturday)

I just got some numbers in on instability for Saturday's hyped-up severe weather outbreak. Even though they're preliminary at this point, I'm already a little concerned. CAPE values (measures instability) are forecast to get near the 2000 J/KG mark, which is pretty unstable. Anything over 1000-1500 J/KG is high enough to support a severe weather outbreak, just as long as all the other elements come into place. The cap (layer of warm air just above the surface that acts as a "pressure cooker" to build up energy) looks like it will be around here until after noon on Saturday before completely getting blown off. This will allow sunlight to heat the surface and energy to build throughout the morning. During the afternoon when the cap disappears, this energy will allow air to rapidly lift upward (instability) and condense at high altitudes. The condensation of this air is what will form our severe storms.

We'll also have to see what happens with shear and surface winds as well on Saturday. I think shear will be adequate for an outbreak, but winds are still a question at the surface. Those will pretty much determine if we'll see a line of storms or separate super cells.

My best guess is that we'll see our standard setup: a few super cells in front of a MCS (mesoscale convective system) line of storms. It just doesn't seem likely that we'd have a tornado mess since we're pushing into July. Stranger things have happened though. Nobody, not even the SPC, can really tell you exactly what's going to happen until just hours before the outbreak. It's simply too far out to tell right now.

Until the rabble-rousing on Saturday, we'll see a small daily chance of thunderstorms and temperatures holding around 90. South winds will bring up moist air and push our humidity up quite a bit, with dew points in the mid to upper 60's (uncomfortable).