Warmer Weather!

Alright, sorry for the really long wait for this blog. . . but the last week has been ridiculously busy, and with finals starting tomorrow, it'll probably be that way for a couple more days. But, right now, I'm taking a break from some of the studying to finally get to discuss the severe weather and bow echo from a couple of weeks ago, and to mention the tornadoes that happened a few days ago around Warrensburg and Sedalia.

Below is the Level II NEXRAD image from 11:36 on that Thursday night, with arrows drawn in depicting wind flow into and out of the line of thunder

storms.

The city in the center of the image is Prairie Village,

with Leawood just to the southeast. I drew in all the rear inflow jet locations (those are the north to south or northwest to southeast arrow) with black. The rear inflow jet is an area of enhanced windflow into the thunderstorm, and, when coupled with enhanced windflow into the thunderstorm from the opposite direction, can lead to 'mesovortices'. Mesovortices are common with bow echo thunderstorms, and are what led to the EF-2 and EF-3 tornadoes in the northland last year. In bow echoes, when shear

and helicity values are high enough, any interaction between the west-east winds of the bow echo and the winds of another thunderstorm, or of a frontal boundary, can trigger the thunderstorm to start rotating, pulling in air from behind (the rear inflow jet) and wrapping winds from the south into the thunderstorm (indicated by the black arrows that move in a curved line generally to the northwest). When this happened, the change in wind profiles are picked up by doppler radar, and small 'hooks' or notches can form on the radar. These are extremely small areas where wind convergence from the bow echo and another atmospheric convective feature is strong enough to produce a brief (but usually strong) circulation. NEXRAD picked up on this and indicated NRO

T (Normalized ROTation) values close to or exceeding '1' around this time, which is typically the threshold where a tornado appears possible. But sometimes, in bow echoes, the west to east winds are so strong that, while a brief circulation is attained with interaction with another convective feature, the winds are only strengthened or pushed closer to the ground, which can often lead to intense downbursts, which are usually localized and known as 'microbursts'. Microbursts cause tornado-like damage, last for only a few minutes or less, and on radar can be hard to discern from tornadoes in severe weather situations. What happened on Thursday, I believe, was a situation where two very small but intense microbursts sent 70MPH+ winds roaring through parts of Olathe and Gardner, indicated by the damage in small areas. Also, the damage was in a relatively straight line. Tor

nado damage is generally very strewn about and sometimes a circular pattern is apparent. This was obviously not the case. But, in DeSoto, where a barn was destroyed, but the houses around virtually untouched, one would have to think that the possibility of a microburst was relatively small considering the microscopic range

of the winds and damage. A localized straight line wind gust or tornado may have been responsible. In bow echoes, when tornadoes do form, they typically only remain on the ground for a few seconds at the most, causing little or no damage to 1 or 2 structures, which I think was very possible in this area.

Below is the radar image with windflow drawn in around the time the damage was reported in JOCO. A notch is visible in the radar just to the northeast of DeSoto.

Any of these 'mesovortices', which are indicated when two areas are pointing nearly directly at each other, have the potential to produce a brief but strong downburst, wind gust, funnel cloud, or tornado. I was watching this very closely of course, and as the storms approached NE JOCO, where I live, I continued to notice the mesovortices and lack of proper warning by media outlets.

Regardless of the type of severe weather occuring, be it tornado or damaging winds, the storm produced damage that was severe enough to be considered life-threatening, and so I think that local media have a responsibility to cover situations like this.

But back to the mesovortices. . . as the storm approached my home, my ears suddenly popped and I heard a loud whooshing sound, I looked outside, and the wind was blowing stronger than I think I've ever seen it, even in a thunderstorm. My ears continued to hurt, and I took shelter downstairs, but the winds subsided within 30 seconds. The next morning, no damage was to be seen. So what happened? Well, first of all, straight-line winds don't normally produce a 'whooshing' sound unless the winds are strong enough to cause severe structural damage. But, funnel clouds can trigger ground pressure changes (i.e. ear popping) and a whooshing sound near by them. While I don't believe the circulation reached the ground, the already gusty winds of the storm may have created a tornado-like scene outside, which is what I saw. Even so, I believe there were probably numerous funnels over head, something most of us couldn't see because of how late at night it was.

So, in conclusion, a mix of severe weather probably occurred. And, tornado-like damage was the result of these dangerous storms. So the message is to take shelter whenever you hear a severe thunderstorm OR tornado warning has been issued. Severe thunderstorms can produce just as much damage as tornadoes but are often not covered as extensively as tornadoes because severe thunderstorms don't carry the connotation that they are highly damaging. I hope all of this made sense, and please share your thoughts!

Anyway, onto the other day near Sedalia. The surface low and front was located nearby, creating ample shear for any surface based storms that formed in the stable environment to produce brief and weak tornadoes, which is what happened. NROT values never indicated a tornado vortex signature or mesocyclone, because of the extremely brief and weak natures of these storms. Luckily, no significant damage was reported and most of the time the storms were in unpopulated areas, but did get frighteningly close to Sedalia.

As for this week- FINALLY! It's hit 80 degrees! And, every day this week we should exceed the 80 degree mark. We might even reach 90 one day this week if the saturated grounds can have some of their water evaporate. A deep ridge has built in over the west, keeping all storm systems well away from KC, and an area of very high pressure has set in. However, if for some odd reason, diurnal surface storms pop up in an extremely scattered fashion, they will warrant some watching as instability is high and marginally severe weather would be possible. But, for the most part, I think this week should be dry and hot! No significant severe weather, but looking at the extended GFS I see at least one. . . maybe two more severe weather days for KC this year, some of which might be more widespread than our prior attempts this year, as warmer air is finally surging in. The earliest chance for any storms is more than a week away, so enjoy the warm air, and make sure to drink plenty of water and wear sunscreen if you're going to be spending a lot of time outside to prevent heat exhaustion and sunburn. Have a great week!

Theory. . .

It's been two days since my last post. . . sorry for the wait! In the mean time, I've studied some damage and damage photos from the storms, along with reviewing radar data, and reading some research papers and AMS reports on 'mesovorticies' in bow echoes, and have come to a consensus on what likely happened late Wednesday night in JOCO. I'll try to post this tomorrow- I've been really busy! In the mean time, enjoy some non-severe thunderstorms this weekend with modest temperatures. Hopefully most of tomorrow will be dry!

Thunderstorms Rapidly Intensifying. . .

12:24 AM UPDATE

After having a little panic attack there (haha), I'm beginning to analyze what happened, and what may still be happening, however I think the bow echo is now, truly, just that- strong, straight line winds. As it intensified east of Topeka, it absorbed many atmospheric disturbances. . . remnants of thunderstorms from earlier today, existing showers, heating from the surface, etc. Riding the cold front, it's easterly movement with winds from the west, and our winds from the south with the passage of the warm front earlier directly contrasted with each other. This created a situation where small, brief tornados could easily develop with any environmental trigger. . . like some of the existing low level clouds and showers over JOCO/Wyandotte from earlier. With the wind contrast and the surface disturbance, shear likely increased, and the updraft-veritcle rotation situation that occured allowed for a brief but scary spin up of a torando, possibly in numerous location. Many damage reports have come from JOCO in the last hour, with 'microburst' type damage, power outages, trees through houses, windows out. . . I've talked to a few people from my area in northeast JOCO who heard the same 'train roar' or loud 'whoosh' noise, something generally assosciated with tornados- especially the pressure drop evidenced by ears popping. So, while these tornados (if they were, remember this is not confirmed) were brief, they were potentially strong. Straight-line winds usually don't blow out windows and send trees through the house. . . they can do quite a bit of damage but that's a stretch. A microburst is possible, but downdrafts indicated a brief tornado threat was more likely. I mentioned this threat before the bow echo came through KC, and obviously it did cause some issues. . . many areas of rotation, many small spin ups likely happened. We'll know in the morning.

For the rest of the night. . . this line of strong thunderstorms will affect central and eastern Missouri, but is currently below severe limits and will likely stay that way. Penny sized hail and 50 mph wind gusts are possible.

More storms are moving up I35 from Emporia towards KC, these too could produce gusty winds and penny sized hail. Right now, I don't believe they will intensify, as our environment is more stable with the passing of the cold front. If something changes, I'll let you know. Flooding will continue to be a threat tonight into tomorrow morning.

This was an interesting night. . . I'll discuss it more tomorrow. Have a good, safe night everyone!

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I went ahead and deleted this portion of the blog as it contained mostly time-sensitive information about warnings.

Severe Weather Update

10:30 PM UPDATE

The line of thunderstorms (none currently severe warned) out to our west by 1 or 2 hours is beginning to bow out, showing signs that some of the winds on the leading edge of these storms is meeting or exceeding severe limits, and a parts of the line have exhibited signs of brief lower-level rotation when they overtook other, smaller, thunderstorms. These may become severe warned with a risk for up to 60-70 mph winds, and a very, very, slight chance for an isolated tornado-

and, well mid-blog the NWS in Pleasant Hill has issued a SEVERE THUNDERSTORM WARNING for Leavenworth and southeast Atchison counties in KS and western Platte county in Missouri until 11:15 PM.

The latest velocity scan out of the Topeka NEXRAD is indicating surface winds pushing 70 mph. Also, the latest scans have indicated a strengthening surface rotation couplet south of Lawrence. I'll watch these storms for the next half an hour or so and update on any new developments.

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All severe thunderstorms in the area have weakened. Flash flood warnings remain in effect for most of the metro until 5:30 AM tomorrow. The tornado watch will expire at midnight along with the severe thunderstorm watch. With the warm front barely clearing KC and strong capping, the severe threat didn't get as dangerous as it could have been. While our thunderstorm outlooks varified (statistically speaking), the situation didn't end up being quite as dangerous as it could have been. For the rest of the night, flooding, which is the #1 cause of weather-related death in the U.S. will be the main threat. Lots of lightning and the potential for some pea size hail to marginally severe quarter sized hail in the stronger storms should be the extent of the remaining threat tonight. A severe thunderstorm watch may replace the current watches across the area at midnight. I'll update if anything very significant materializes- but right now I don't think there's much of a tornado or damaging wind threat tonight. Tomrrow will be much cooler (most of the day in the 50s!) and rainy through the morning. We'll summarize the severe weather reports from today tomorrow evening. Have a good night!

Thunderstorms Forming. . . Outlook Update

Funnels have already been reported over central KS, near Hutchinson, and a tornado has just been confirmed on the ground northeast of the city, near McPherson. Multiple tornado warnings and numerous severe thunderstorm warnings are in effect for the western portions of Tornado Watch #155 (which includes Jefferson and Douglas Co. in Kansas). These thunderstorms are primarily linear but have embedded supercellular structures allowing for a significant tornado threat with these thunderstorms. The warm front is moving through the KC area right now, with temperatures in JOCO in the upper 70s, but only 61 at MCI Airport. Clouds have held over KC but instability is growing with the advancement of the warm front. A relatively strong cap is holding in the atmosphere over KC, but has already been broken just west of Wichita. This has led me to shift my 'Greatest Risk' area to the southwest, and I've left KC out of that outlook region. I believe the highest tornado threat will be well southwest of KC today, with atmospheric conditions becoming more probably there with the already unstable and saturated environment. I've included KC in the 'Likely' area because of a significant threat for large, damaging hail, and isolated tornados. Farther to the north and east, large hail will still be possible, in some of the stronger storms ahead of the warm front. That is why I've kept those locations in the 'Possible' area for severe weather. As for here in KC, please continue to monitor this situation as the situation in southern Kansas is quickly involving into a significant severe weather event. Large, damaging hail will be the greatest threat with any of these storms. I've posted my updated outlook for tonight along with a tornado watch graphic below. I'll update later on.

Latest Model Trends

The 00z NAM has been released, and SREF parameters have been updated. Confidence is increasing in this event for tomorrow. Alot of the questions that I posed in my previous post are somewhat clearer. I have great confidence that KC will hit 80 degrees tomorrow. The dew point will rapidly climb to nearly 70 degrees in the afternoon. The latest models show sufficient helicity along the surface boundaries to support surface supercells. The cap should be broken in the afternoon/evening because of extreme forcing. Instability will be very high- the atmosphere will rapidly destabalize in the afternoon leading to ML and MU CAPE >3000 j/kg. The LLJ should intensify and combine with existing shear in the atmosphere to allow for a small window of potentially significant tornado threat. The latest supercell composite, which maxes out at 12, has the entire region in that '12'. Supercells are very likely. Surface based supercells should also form early on in convective development near the surface boundaries in the saturated warm sector. This means that from Lawrence. . . to St. Joseph. . . to Kirksville. . . to Marshall. . . to Ottawa. . . and back to Lawrence, a region will emerge where a potentially volatile tornado situation could take shape sometime in the late afternoon tomorrow. 5PM-8PM is my best guess. We now begin to nowcast. . . and make forecasts based on current surface observations.

For tonight, strong thunderstorms are developing south of an Iola to Clinton line. Pea sized hail and vivid lightning is likely with this storms. I don't think these storms will result in any severe weather threat.

For tomorrow, here are my main points:

• Before 12PM- showers and thunderstorms around, moving to the north. Pea sized hail, gusty winds, and lightning are likely. Severe hail isn't out of the question but is becoming increasingly less likely.


• 12PM-5PM- skies will clear out and temperatures will climb to around 80 degrees, with an extremely humid summer-like airmass in the city. Clouds may start to build toward the end of this period. Pay close attention to forecasts for later in the night.


• 5PM-10PM-Our confidence in a SIGNIFICANT SEVERE WEATHER EVENT for KC is growing with each model trend. During this time, destructive hail, severe wind gusts, and tornados will be possible with any storms that develop. Make sure you stay up-to-date with the latest forecast information. Also, ensure that you and/or your family have a severe weather plan ready to be implimented should a tornado and/or severe thunderstorm warning be issued for your area.


• 10PM and on-Another round of severe weather is possible as the cold front moves through. Very large hail and damaging winds are possible, especially if a bow echo can form. The tornado threat is relatively low with these storms, but the formation of a couple of brief tornados is not all that rare on the leading edge of a bow echo.

My updated outlook is below. Remember, things still can change, but let's hope for the best, and prepare for the worst. Have a good night everyone, keep in mind tomorrow will feel so much better than all these cold days we've been having- and, the severe risk, while significant, should only last a few hours in the evening.

A Recap of Yesterday and Model Trends

Let's take a look back at what happened yesterday. An unusually moist, but cool, airmass surged northward into northeast Texas, Oklahoma, and extreme southeast Kansas. A very well defined dry line pushed eastward extending south from a surface low in south central Kansas. Shear and helicity values were off the charts. CAPE was nearing or exceeding 3000 j/kg (indicating extreme instability). Shortly after noon, isolated thunderstorms produced a couple of tornadoes in far west Kansas, prompting the SPC to expand their moderate risk westward- something that would soon prove to be an excellent idea. By 2-3PM, storms fired along the dryline in north central Oklahoma and south central Kansas. These storms became tornadic in well under an hour, producing multiple large wedge tornados. One tracked from near Enid to well east of I35. Another moved from near the OK/KS border into Arkansas City, producing damage. It continued to move rapidly to the northeat with periodic tornado reports continuing. Wichita was tornado warned for quite some time, and tornados were reported around Mid-Continent airports, however no damage was reported in Wichita's city limits. Farther south, disorganized convection formed near OKC and quickly became surface based, dropping a few tornados in and around the city. The most significant of these formed on the south side of the city of Norman. KWTV captured the massive funnel as it touched down and destroyed nearly 50 houses, damaged many more, and, tragically, caused a few fatalities. This tornado remained on the ground for an unknown amount of time- reports of a tornado came in until around 9PM but it is unknown whether this was one or multiple tornados. Most likely, this storm produced 5 to 6 tornados, with 2 or 3 being large and destructive. In southern Oklahoma, multiple tornados, including one large wedge tornado, were reported in the Ardmore vicinity. As I said earlier, the SPC is lucky to have extended the moderate risk westward. The bulk of the tornados occured either in the moderate or slight risk areas. The well publicized high risk area saw only 3 tornados, all on it's edge. The Arkansas City and Enid tornados moved into the extreme western portion of the risk area, and the massive long-track OKC tornado skirted highway 44 on the southern edge of the risk. So, overall, it was an excellent chase day. Amazing data has been collected and there are many beautiful pictures. However, this day will best be remembered for the tragic fatalities of at least 5 Oklahoma residents who lost their lives to these massive twisters.

Initital damage surveys have indicated some of these tornados may have had wind speeds characteristic of upper-end EF3 tornados.

So for totals: about 10 different tornados were likely spotted yesterday. 42 total tornado reports, 49 severe wind reports, and 67 severe hail reports combined for a significant total of 158 preliminary severe weather reports.

As for tonight. . . the warm front will push to as far north as a Mound City, KS to Camdenton, MO. Along and ahead of this front, marginally unstable air, marked by CAPE values nearing 1500 j/kg, will push to the far southern reaches of the KC area. Any convection that can form will be elevated, and upper level winds appear to be at least somewhat supportive of a widely scattered marginally severe hail threat. This hail threat should stay south of KC, but some pea sized hail along with vivid lightning will be possible through tomorrow morning. By noon, the warm front should be near I70, and skies around KC may begin to clear. But here is where things get tricky- at some point tomorrow the warm front will clear I70, and we think it'll be around noon. But, this may happen earlier if tonight's LLJ can propel it into central MO faster. It may happen later if wind fields aren't supportive of frontal convergence or movement. Also, it could slow down if morning convection cools areas north of the front enough necessitating a higher concentration of the warm and moist airmass behind the warm front.

After it crosses the I70 corridor, it may drift gradually to the north but should stop well south of MO highway 36. Above the lower levels of the troposphere, a warmer air mass will be forced over the area, effectively capping the atmosphere until significant destablizing of the airmass can occur with convergence along the boundaries. Below is my best guess as to where the surface boundaries will set up tomorrow evening.

The low will be rapidly moving into far northeast KS by 7-8PM. By this time, KC should have reached 78-80 degrees in temperature, and close to 70 degrees in dew point. Below is the GFS temperature prediction for tomorrow evening.

The deep red are temperatures in the upper 70s, and the first purple gradient is 80 degree temps. By tomorrow evening, the atmosphere should have destabilized creating a moderate to extremely turbulent atmosphere. The latest model compilations have pegged ML and MU capes between 3000 and 4000 j/kg for around this time. With the significant instability and pooling of warm, moist air concentration in the narrowing warm sector between the cold front and the warm front, some storms should be able to form and punch through the cap. Any storms that form in this saturated air mass will likely evolve to become severe within minutes of their formation. Areas along the warm front and along the cold front will have a small window when a potentially significant tornado threat may be posed. This is the area where highest helicity values will be present- storm relative helicity is one of the few inhibiting factors we have in this instance. Any areas of signficicant convergence should see helicity values rise into levels needed for surface based convection. Deep boundary layer moisture will further this threat along the fronts. Also, the closer to the low, the higher the risk of rotating storms. In this area, winds will be spinning more rapdily than other areas. So the set up is there for a potentially signficant, and somewhat widespread, severe thunderstorm and tornado outbreak across the area. But, there are some variables we are now uncertain on that will greatly sway tomorrow's threat.

1) Helicity values. Before 3 or 4PM, storm relative helicity values generally necessary for tornadic development will be very high. However, by the time convection can start to form, higher helicity readings appear to be retreating into Iowa and Nebraska. If convergence is strong enough coupled with the pooled moisture along the fronts and in the warm sector, we may see an isolated spike in helicity, which, right now, looks to have a good chance of happening. I'd go 60-40 that somewhere in the warm sector, close to the fronts and surface low, helicity values rise high enough to support surface rotation.

2) Warm front position and cloud cover. The warm front is forecast to move slightly north of KC by tomorrow evening. I'd say this seems very likely. But, KC's severe chances rest on the warm front's proximity to the metro. Areas along and just south of the front have the highest threat, and right now, if everything works out the way things are looking right now, it should be positioned north of KC. The farther away from KC, the lower our risk for any surface based storms. Also, a layer of low-based clouds may spread over KC late in the morning with some of the thunderstorms. If cloud cover can remain, my temperature prediction may not verify, especially if rain continues later into the afternoon than I am thinking it will. I would say that the chance of the warm front being positioned just north of KC isn't good, but it is our best prediction as of now. I'd say there's about a 60% chance that we'll adjust this frontal position north or south more than 40 miles in our future forecasts. I would also say that there's around a 30% chance that morning convection and clouds will inhibit instability.

3) Timing. Any tornado threat will be short lived. It should be focused around the extreme north section of the cold front near the low, and east along the warm front. Any slowing or speeding up of this system may change my timing predictions, although with every model release we are gaining confidence on the relative location of the cold front and surface low.

So, all in all, I'd say we have to watch this very closely. If things setup like their looking now, severe weather will be likely. But, the biggest question is how our tornado threat will shape up. If frontal convergence and moisture pooling occurs close to KC, or the atmosphere retains favorable helivity values, our threat will be greatly increased. But, as I pointed out above, this is very conditional and right now I don't have a significant amount of confidence in my prediction. Below, I've outlined where I think the best chances for severe weather will occur based on current trends, but remember to take this with a grain of salt. Or should i say many grains of salt? Uncertainty is high right now and there's a good chance models later tonight into tomorrow may greatly change my prediction. Regardless, it's a good idea to keep a NOAA weather radio around and an eye to the sky, to the forecast, and to local media for information on this rapidly evolving severe weather potential.
I'll update later tonight or in the morning. So many questions in this forecast- I hope my analysis made some sense. Have a good night and keep an eye on the weather for tomorrow evening.