1/29 - 5:45pm - Serious Severe Weather Concerns Tonight

Latest Severe Weather Updates

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A severe weather setup that we see normally in the springtime is about to unfold on this late January night across a large expanse of the Southeast. While not "unprecedented" or "once-in-a-lifetime", this outbreak is going to impact quite a few people and it's important that everyone have what they need to be prepared and safe. This post is mainly for folks in North Mississippi and West Tennessee, but you can figure out pretty well how you'll be affected if you're not in these areas by some of the maps and information below. Everyone needs to be aware of what's going on because this will be happening at a very bad time of night when even the night owls are asleep.

Fast Facts

A MODERATE Risk of severe weather has been issued by the Storm Prediction Center for the overnight hours in West Tennessee and most of North Mississippi. Tornadoes, damaging winds, and hail are all on the table for these areas as storms move through. Even though places like the Golden Triangle in Mississippi are just outside of the Moderate Risk area I would treat this as if you were in it because these storms are going to be very, very strong still as they move through this region. Please, please, please have a weather radio or smartphone app that's armed and ready to alert you if a Tornado Warning is issued for your location tonight. This will be hitting when most people are asleep so it's a very dangerous situation.

Timing - North MS and West TN

8pm - Midnight - Small chance for some isolated storms. These would carry a tornado, wind, and hail threat.

Midnight - 2am - Slightly better chance for isolated storms, small line of storms may try to form ahead of main line.

2am - 7am - Main line of severe thunderstorms moves through. This will affect everyone. Tornadoes, severe damaging winds, and hail are a good bet during this time.

Discussion

A line of storms stretches from the Great Lakes to Texas right now and will continue to move eastward through the evening. A few reports of severe weather have come in already from this but the main show will be overnight as this line of storms encounters a more rich environment for severe weather.

The main storm mode for tonight will be a squall line of storms with embedded rotation in portions of it (AKA what's termed a QLCS). Supercell storms will be possible ahead of the main line of storms too and could easily produce tornadoes if they develop. Tornadoes in QLCS lines of storms like the one we'll have tonight are more difficult to identify on radar since they're embedded within the line. While not as strong as supercell tornadoes, QLCS tornadoes can be strong and cause massive damage in the right environment.

While directional shear, which is needed to produce tornadoes, isn't very good for this event, the speed shear or tendency for winds to increase in speed with height will be very good. But, the directional shear may just be enough to cause problems. When you combine helicity (caused by shear) with instability in a formula you get what's called the Energy Helicity Index (EHI). This, in my mind, is a good determinant of tornado ingredients in an environment. The NAM model has increased levels of the EHI throughout West Tennessee and Mississippi tonight as this squall line is moving through so these QLCS tornadoes may have some kick to them if they develop. Not good news at all.


Also, since winds at 850 mb (about 5,000 feet) will be howling it will not take much for any part of this line of storms to pull these winds down to the surface and create straight-line wind damage. I wouldn't be surprised if folks affected by the worst of these winds thought they were hit by a tornado. I'm hearing the word Derecho being thrown around a bit with regard to how this system will develop tonight. That's certainly a possibility with this system but I think it's a relatively small chance.

One more thing to mention, and this is not the least important at all, is the fact that moisture and warm air continues to stream in from the south in advance of this system. When the dry line that's triggering these storms hits this richer air tonight you'll know. The whole line of storms should really begin to light up by then. Having air this warm and moist in January is never a good thing because Mother Nature intends to correct it in a violent way.

Follow me on Twitter and my Facebook page for the latest updates tonight!

6/28 - 11:30am MDT - Waking Up in Nebraska

After storms in Northeast Colorado yesterday became contaminated by storms coming off the Front Range, we decided to head east to be ready for today's chase. After waking up in Ogallala, Nebraska this morning we're rested up for a relatively leisurely day without too much driving since we're already pretty much in our target area for the day. The Storm Prediction Center has a general thunderstorm risk out for Western Nebraska, Northeast Colorado, and Northwest Kansas today with a 5% severe wind risk.

The focus today will be a cold front that's slowly moving through the region today. Winds around this frontal boundary may shift out of the east a little bit and that's where we'll position ourselves since the best shear will be where that happens. Dew points will be in the 60's across Central Nebraska this afternoon with slightly lower readings to the west. These surface winds, while weak, and the moisture should be more than enough to get some storms going.

Winds aloft are a little less certain since they may change throughout the day. Early on this morning winds at 500 mb (18,000 feet) were almost westerly across the western half of Nebraska, but already we've seen a shift to the southwest. While not terribly strong, the winds up there could have just enough punch to get storms to become severe. Small embedded shortwaves within the flow may enhance these winds a bit in some areas too. By 6pm MDT tonight the RAP model (right) still has these winds out of the southwest aloft, so that's some good news. The thinking at this point is that the shear won't be high enough to keep storms from merging together and being clustered, but we'll see how that plays out.

Follow me on Twitter and Facebook for constant updates during our chase!

6/26 - 10:40am MDT - Another Day, Another State

Yesterday near the Black Hills of South Dakota we saw a few storms develop but they never got organized enough to be good for chasing. One storm in particular had some promise but it just couldn't get strong enough to leave the elevation of the Black Hills where its updraft was rooted. Today we're going north from the Black Hills and moving into North Dakota where there should be a threat for severe storms this afternoon. In particular, areas near and just west of Williston, North Dakota into extreme Eastern Montana appear to be under the greatest threat since a few isolated storms could produce hail, wind, and maybe even an isolated tornado. The Storm Prediction Center only has a general thunderstorm risk for this area but there's a 2% tornado risk included. You'll see the Slight Risk up there in Montana as well in the map to the right, but that area is very remote and the surface winds likely won't cooperate as well for storms like they will in North Dakota.

Winds aloft are forecast to be stronger in our target area today than they were yesterday in South Dakota since the upper-level disturbance over the northwestern part of the country will be moving east a little. When you couple these stronger southwesterly winds aloft with southeasterly winds at the surface that can create some shear for rotating storms. It's worth noting that the best surface winds could be in Canada just north of North Dakota and Montana since an area of low pressure will be spinning winds around from the east there. Since we can't go to Canada, that's obviously out. Dew points in North Dakota are downright soupy this morning and will likely continue to be that way through the afternoon. Having 70 degree dew points right on the Canadian border is something you don't see too often.

With all the warm air and moisture in place, instability will be plentiful for storms. I talked about the threat of isolated tornadoes today on the SPC's outlook and that may very well verify if the instability and shear come together. A great way to combine those two factors is to look at the Energy Helicity Index, which starts getting higher in an isolated spot in Western North Dakota according to the RAP Model. We'll see if it's enough to get some good storms going this afternoon and evening!

Keep up with our chase today by following me on Twitter and Facebook!

6/25 - 10:30am MDT - Great Faces. Great Places.

Today's blog post title is the South Dakota's state slogan. As you can probably gather by that, we're in South Dakota today! Southwesterly flow aloft at 500 mb (18,000 feet) will be present in the western half of South Dakota, northwest Nebraska, and Eastern Wyoming today as the general pattern we dealt with yesterday continues. While the winds aren't terribly strong, the RAP model is beginning to pick up on an area of enhanced speeds near 30-40 knots around parts of Western South Dakota and Northwestern Nebraska. If this enhanced area verifies there could be some better storms under it.

At the surface right now there are southeasterly winds across this area, but the more easterly of the wind vectors are favoring Western South Dakota right now. We'll see how this develops throughout the day as surface conditions continue to change. We'll want these more easterly wind vectors becuase they'll contribute to low-level wind shear that could possibly lead to rotating storms, should they form.

I say "should they form" because we're still dealing with some very warm temperatures aloft. These warm temperatures aloft, called "the cap", inhibit storm development because rising air parcels can't continue to rise buoyantly if the environmental air around them is warmer than they are. The good news here is that temperatures at the surface today will again be in the 90's to near or above 100 degrees. This will really heat up these surface air parcels so that they might shoot through the cap. All models I've looked at this morning have the cap breaking at some point in the early to mid afternoon, but where exactly this happens is still in question. The 14z RAP model has an interesting hole in the cap at around 4pm near Rapid City, but our current thinking is that the Black Hills near Rapid City will be a focus for storm development because they are a constant source of lift and thus a typical location for storm initiation.

To get some of the heating we'll need for storms to form today, we need to have a plentiful supply of sunshine. Right now we do have a layer of clouds over South Dakota that is inhibiting this right now, but western parts of the state are clearing out and it should hopefully leave us with blue skies later this morning. Storms should form sometime after 3pm this afternoon should things come together as forecast. The main threats will be wind and hail from any storm that forms, but we'll be on the lookout for some rotation in these storms as well. The Storm Prediction Center has a general thunderstorm risk for our target area today, but also mentions a 5% severe wind and hail risk.

Follow me on Twitter and Facebook for the latest updates this afternoon!

6/24 - 10:35am MDT - The Chase Begins!

This morning we're heading toward Cheyenne, Wyoming from Denver as we continue to look at weather data coming in. Today's setup still looks marginal by most accounts, but there are a few small features that could cause a few isolated storms to go severe. For one, surface winds out of the east in Wyoming, Northeast Colorado, and Nebraska will generate upslope flow, which is the lift mechanism we need to get storms going.

These winds will also create some shear because they will be interacting with southwesterly winds at 500 mb (18,000 feet). The issue with this is that the faster winds at this level will be further north toward Rapid City, South Dakota instead of where the more favorable surface winds will be just to the south. In any case, the wind direction at 500 mb will be good enough to usher in the wind shear and maybe some drying of the air at that level to increase instability.

When you put the expected helicity (caused by wind shear) and the instability together for today, you get the Energy Helicity Index (EHI). According to the 14z RAP model, the EHI may try to ramp up a little bit in Northeast Colorado and it even breaks out a little bit of precipitation just west of there too. Surface heating is going to be massive since temperatures will be in the 90's and 100's in some places, so we're hoping this also helps overcome some of the warm temperatures aloft (the cap) so that isolated storms can develop. We're grasping for small features today since there isn't any one thing jumping out to get our attention, but so far it looks like a storm or two could fire on the elevation near Cheyenne. We'll also be watching an area closer to Rapid City, SD to see how things develop up that way.

Follow my continuous chase updates on my Twitter and Facebook accounts today!

5/25 - 11:50am CDT - A Grand Finale

Ever since earlier this week we've had our eye on today's setup in Central Kansas. The moisture return, a low developing over Southwest Kansas, and upper-level wind support all kept us coming back to look at the models to see how it was shaping up. For a while it looked like the cap, or a layer of instability-inhibiting warm air aloft, was going to surpress storm formation but now we're seeing a situation where there will be just enough break in the cap to allow for a few isolated supercell storms to form. To get surface heating today to break that cap we need to clear out the clouds across Kansas first. A push of dry air at around 10,000 feet is currently moving from Southwest Kansas to the northeast and is eating these clouds for breakfast as you see in the satellite image to the right. We expect this to keep moving throughout the day and hopefully it will clear out the clouds in time to get some serious surface heating going.

The big story here today is the moisture return. For the first time this week we are seeing a situation where dew points will surge into the mid to upper 60's. Yes! This much-needed moisture will be the fuel for storms this afternoon and should give us a much better show than the moisture-deprived low-precipitation storms we've been seeing lately. While we don't have this moisture in the area quite yet, it's streaming in like crazy right now. Strong easterly and southeasterly winds are blowing this moisture into Kansas from Missouri and Oklahoma and will continue doing so throughout the day. Having mostly easterly winds in Kansas right now is a very good thing because this is creating just about optimal low-level shear for rotating supercell storms.

Speaking of wind shear, this will create quite a bit of helicity, or a corkscrew-like rotation of air in the atmosphere. When you combine helicity with instability in an equation you get the Energy Helicity Index (EHI). As I've said before I think that indicies and parameters can be distracting since human analysis is always better than a formula, but EHI seems to be fairly reliable since it is so basic and relies on two very basic ingredients. This afternoon's EHI values in Kansas will be the highest we've seen out here this season according to the Rapid Refresh model. That's some great news for storm chasers because higher EHI values typically correlate with enhanced tornado potential.

The Storm Prediction Center has a Slight Risk for severe storms today from Iowa to the Texas Panhandle and within that a 5% tornado risk in Kansas. This is quite the change from the previously non-severe "general thunderstorm" outlooks that they had been issuing for today because of the concern that strong capping may inhibit storm development. Today is our last chase day out here for Tour 3 and my last day out here until I come back for a week in June. If we could see some good storms today that'd be a great end to the first part of my trip! Tonight once we're finished chasing we'll be traveling back to Oklahoma City where I'll fly back to Louisville from tomorrow morning.

Follow up-to-the-minute reports on our chase on my Twitter and Facebook accounts!

5/22 - 9:45am MDT - Nebraska Here We Come!

Today's storm setup is tricky because we're dealing with, again, a situation where the moisture is not returning to the region as well as we need it to. The good news though is that the trough that is slowly making it's way eastward will finally be in play today, so upper-level wind support will be there for storms. Let's start with the moisture though. The higher dew points will be in the Dakotas today no doubt, but this is at the surface. With such a short time between being dry and having moisture moving into that region, this moist layer is likely very shallow and confined near the surface even though the short-range models this morning show it a little deeper than before (models have not been handling moisture well at all lately). This means that storms up that way would likely be low-precipitation supercells, maybe to the point where some of them are only putting down virga and not ground-falling rain. The better surface wind support near the low will also be in the Dakotas, but you won't get many, if any, tornadoes if the storms can't get any "meat" on them from the lack of moisture. Dew points in Northern Nebraska may be lower at surface, but we may have an overall deeper layer of moisture there.

The upper-level winds as I said before will be more favorable today than yesterday. The trough moving in will provide fast southwesterly winds in the Dakotas extending down to Northern Nebraska. This should bring in some drier air aloft and enhance wind shear for this afternoon's storms. Today we'll stay on the southern end of these winds aloft so that maybe we can get some deeper moisture coupled with the winds. Hopefully some supercell storms can form in this environment.

Because the models are having difficulties resolving moisture issues, today's CAPE (instability) forecast looks rather low in Nebraska with higher values north. This is something we'll be watching throughout the afternoon to see where it actually sets up. The potential lack of moisture and the best shear being removed from deep layer moisture will likely limit tornado potential today, but maybe we can see some high-based photogenic storms!

The Storm Prediction Center has a Slight Risk for severe storms today in the Dakotas extending toward Northern Nebraska. There's only a 2% tornado risk with this and I think this is a good call given the moisture issues here. If dew points were to be higher over a deeper layer in North Dakota I think you could have a pretty decent tornado risk from supercells given the forecast wind environment. In any case, our more southerly target today will put us in great position for tomorrow's chase, which will likely be in Nebraska.

Follow me on Twitter and Facebook for updates today!

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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5/20 - 11:45am CDT - Texas Panhandle Today

We're on the road from Oklahoma City to the Panhandle region of Texas where storms are likely to form today. Right now we're watching a clear area on satellite near a cold front situated just south of a line from Childress to Lubbock, TX. This clearing should help to build instability for storms to form as heating from the sun is allowed to reach the surface. Winds and dew points at the moment are not terribly favorable, but the most recent RAP (Rapid Refresh) model does have surface winds turning more easterly during the afternoon bringing in more moisture.

Even though winds at the surface will likely be favorable, winds aloft at 18,000 feet (500 mb) will be weak and westerly to west-northwesterly. It would be preferrable to have winds at that level that are fast and from the southwest, so not having much of either of those components will be a limiting factor. Storms that form this afternoon could have some large hail and winds, but the tornado threat at the moment looks marginal given the lack of upper wind support and possibly lower dew points.

Given these factors, the Storm Prediction Center has decided to forgo issuing a severe weather risk for the area today and only has a general storm risk with mention of some isolated instances of severe storms. The trick today will be to find these isolated instances wherever the best environment for these sets up this afternoon.

The latest updates on our chase are available on Twitter and Facebook.