May 202013
 

Sunday, 19 May 2013

 

Violent stovepipe tornado near Dale, Oklahoma on May 19, 2013.

Violent stovepipe tornado near Dale, Oklahoma on May 19, 2013.

What a day! After seeing some very photogenic tornadoes yesterday in Kansas, I couldn’t have imagined actually seeing even more impressive tornadoes today. But I did. I documented a multi-vortex rope tornado in Edmond, a wedge near Carney, and a violent wedge/stovepope tornado near Dale Oklahoma.

Here are just a few screen shots from today. Much, much more to come as time permits of course!

 

Violent wedge tornado near Dale, Oklahoma on May 19, 2013.

Violent wedge tornado near Dale, Oklahoma on May 19, 2013.

 

Stovepipe tornado near Dale, Oklahoma on May 19, 2013.

Stovepipe tornado near Dale, Oklahoma on May 19, 2013.


 
Tornado near Carney, Oklahoma on May 19, 2013.

Tornado near Carney, Oklahoma on May 19, 2013.


 
Tornado near Carney, Oklahoma on May 19, 2013.

Tornado near Carney, Oklahoma on May 19, 2013.


 

Jim

May 192013
 

Sunday, 19 May 2013

 

Tornado just south of Rozel, KS with a lightning bolt on May 18, 2013.

 

It’s now the very early morning hours after the chase, so I’ll make this brief. Yesterday (May 18) I witnessed two tornadoes in western Kansas near the town of Rozel. The first developed into a large cone/stovepipe tornado which I witnessed from very close range. The other was an elephant trunk that had one of the longest rope out stages I’ve every seen. These tornadoes were very photogenic and slow moving. What a fantastic chase day!

 

Tornado south of Rozel, KS on May 18, 2013.

Tornado south of Rozel, KS on May 18, 2013.


 
Tornado east of Rozel, KS on May 18, 2013.

Tornado east of Rozel, KS on May 18, 2013.


 

I wish I had time to write and post more but I need to get some rest for tomorrow’s chase day! As time permits I’ll post more photos and updates.

 

Jim

May 172013
 

Friday, 17 May 2013

 

I’m sitting here at an airport, waiting for my connecting flight taking me to the Great Plains, and I’ve FINALLY found a free moment to post about what I’m doing! The last few days/week (mostly the past 48 hours!) have been incredibly busy and stressful with work and life. I had been waiting and waiting for the MJO to reach phase 5 to bring a good chase pattern and it finally has, right at the worst possible time logistically for me!

Nevertheless, despite having a million and one things to do, I’ve put things on hold for the next few days for storm chasing. This is just how it works sometimes and it kinda sucks. I’m exhausted and I have a lot of things waiting for me to do when I get back from this trip. But, the atmosphere brings together conditions likely to produce tornadoes when it wants to. And I think it wants to this weekend through early next week when a series of storm chasing setups will bring the potential for tornadoes – some violent – across the Great Plains. The combination of upper level support, shear and especially instability on a couple of these days looks very impressive as a result of very deep, rich low level moisture. So I want to be out there, and I’ve done literally everything I can to make that happen. After all, this is what I’ve been waiting for!

More to come soon as time permits…

 

Jim

May 112013
 

Saturday, 11 May 2013

 

In just typing today’s date I get an odd feeling. May 11? Yep, we’re well into the second week of May and not much has happened. I found myself rather excited a few days ago, I believe it was May 8. There was a legitimate, half decent chase setup over western north Texas and Oklahoma, featuring the likelihood for supercells to form off the dryline and bring the potential for a tornado or two (see image below). It wasn’t a great setup, but at least it was a setup.

 

Visible satellite image over the southern plains on May 8, 2013.  Supercell thunderstorms are occurring along the dryline from west Texas north into western Oklahoma and Kansas.

Visible satellite image over the southern plains on May 8, 2013. Supercell thunderstorms are occurring along the dryline from west Texas north into western Oklahoma and Kansas.

 

I have a friend that went chasing that day and I did some nowcasting for him. It reminded me how much constant data you need as a storm chaser to make sound decisions on which storm to go after and when to drop your storm and go after another. It brings me back to days when you are on a storm, fumbling through a map to find the number of the highway heading north. You think to yourself, “How many miles do I have ’till I get there?” You take a closer look at the map, “Ok, 13 miles before we get to that east option, I think we can beat that hail core!” You reach for your camera to snap a picture of a wall cloud, but you do it quickly because you’re also driving. The hail core is getting closer. Now the road is only a few miles away. You’re cutting it close but you’ll make it. Before you know it you will be on that road going east, looking for the updated radar image. Yes, storm chasing is exciting but it’s also extremely stressful at times.

On May 8th there were storms forming along the dryline over the eastern Texas panhandle and western Oklahoma (see image below). The CAP was strong but there was a shortwave moving through the region during peak heating. So the storms which formed had a window of opportunity to become severe and perhaps produce a tornado. But once the shortwave moved too far east the supercells began to struggle with the CAP and the day was pretty much over. It’s sad this setup got me so excited. But like I side, it was at least a legitimate chase setup, and in this slow season those kinds of setups have been few and far between.

 

Radar image (base reflectivity) showing supercell thunderstorms across western north Texas.  I helped direct my friend to the storm just south of Memphis (see arrow).

Radar image (base reflectivity) showing supercell thunderstorms across western north Texas. I helped direct my friend to the storm just south of Memphis (see arrow).


 

In the image above and the image below, you can see a nice supercell south of Memphis, but it weakens. At one point it had a hook like feature on the southwestern side of the storm along with a v-notch. But the storm began to weaken (image below) and the southern storms started to intensify. However, the CAP was beginning to strengthen again as the shortwave moved east of the storms. Thus, the best part of the chase day was likely over.

 

Radar image (base reflectivity).  You can see the storm my friend is on is weakening and the storms to the south seem to be intensifying.  He decided to drop south to one of the southern storms (see arrow).  Unfortunately, the CAP was strengthening again as the shortwave had already passed east of the region.  Thus, none of these storms had much of a future anymore.  But diving south on bigger days can a lot of times be very rewarding.

Radar image (base reflectivity). You can see the storm my friend is on is weakening and the storms to the south seem to be intensifying. He decided to drop south to one of the southern storms (see arrow). Unfortunately, the CAP was strengthening again as the shortwave had already passed east of the region. Thus, none of these storms had much of a future anymore. But diving south on bigger days can a lot of times be very rewarding.


 

This day sorta reminded me about all the little things you deal with while out storm chasing. The hours upon hours in the car. The daily search for food. And while we try to have balanced meals, good luck doing that every day! The lack of solid nutritional meals really takes a toll on the body after a few days, i.e. stomach acids. Factor in a major lack of sleep and a lot of driving and you get the picture. Before you know it you’re exhausted. You’ve been chasing marginal setups every day for a week and your body is just drained. You’ve been getting storms, some supercells, but no tornadoes.

Then you finally get a great setup with a good possibility for tornadoes. You’re still exhausted and your body has been beaten down by sleep deprivation and malnutrition. But you press on. Adrenaline kicks in and the pain is numbed. It’s time to finally get that tornado, but it’s going to take hours of forecasting, navigating and really tough decisions. Oh right, it’s also going to take a little bit of luck! That’s because sometimes the most amazing supercell just refuses to produce a tornado, while the storm to your north for whatever reason drops a huge wedge tornado. Do you have time to get there before it dissipates? This is storm chasing.

 

Jim

May 042013
 

Saturday, 4 May 2013

 

It’s hard to believe we are already halfway through the first week of May! You wouldn’t know if you are looking at forecasts from the Storm Prediction Center showing a lot of “See Text” areas or looking at the way the weather has been the last several days. With historical snowfall and record low temperatures occurring from Colorado to Kansas and other areas of the Great Plains, it just hasn’t felt like spring. Not at all. In fact winter hasn’t given up. But I’m finally seeing the beginning stages of spring and yes, the storm chasing season, coming back to life!

Right now as I type, a large area of thunderstorms (convection) continues to grow over the Indian Ocean from just east of Africa to just west of Indonesia (seem image below). This is the birth of a new MJO (Madden Julian Oscillation) wave. And the future strength and especially movement of this MJO could have a significant impact on the storm chasing season in late May or early June. So it has this storm chaser’s full attention.

 

Satellite image on May 4, 2013 over the tropics from eastern Africa to the Indian Ocean and Indonesia area.  The MJO convection is circled.

Satellite image on May 4, 2013 over the tropics from eastern Africa to the Indian Ocean and Indonesia area. The MJO convection is circled.


 

Ok, please brace yourself for three paragraphs of a bit of meteorology (weather nerd) talk. It’s necessary to explain how all this stuff can result in large tornadoes! Below is the MJO forecast for the next 15 days from the European Ensemble. Notice how most members bring the MJO to phase 4 in about two weeks while a few bring it all the way to phase 5. Phase 4 would certainly bring more troughs to the west coast of the U.S., but it would be a split flow type pattern with a continued ridge over western Canada to Alaska (not shown). This would probably bring severe weather setups to the southern plains (TX/Oklahoma) from the subtropical jet, with some limitations given that the main jet energy source would be blocked.

 

MJO forecast for the next 15 days from the European Ensemble valid May 4, 2013.

MJO forecast for the next 15 days from the European Ensemble valid May 4, 2013.


 

However, the greater pattern impacts which would bring the potential for a lot more significant storm chasing setups to the Great Plains, would occur if the MJO makes it out to phase 5 (see image below). Phase 5 would bring a full jet stream extension across the northeast Pacific (ridge just south of Alaska) and a corresponding trough to the western U.S. and western Canada with a ridge over the southern U.S. Basically, it would bring a great synoptic scale weather pattern for severe weather and potentially tornadoes to the central parts of the U.S. including the Great Plains. Just how long this good chase pattern lasts would largely be dictated by just how long the convective feedback remains in phase 5.

 

500mb height anomalies for MJO phase 5 during the month of May.  Should this occur in late May it suggests a favorable storm chasing pattern.

500mb height anomalies for MJO phase 5 during the month of May. Should this occur in late May it suggests a favorable storm chasing pattern.


 

Ok, now that I’ve talked about how great it would be for storm chasers if the MJO makes it all the way to phase 5 and those convective feedbacks remain in place, we can talk in a bit more realistic sense. It’s a bit unclear just exactly how quickly and how far east the MJO will move over the next 15 days. I’m not seeing a lot to suggest significant eastward progression right now, based on current data across Asia and the Indo-Pacific region. Though some data strongly suggests quick eastward movement over the next week, or at the very least continued strength of the MJO wave. Beyond that again it’s unclear how far east this MJO will go at this time. But the one thing that convection has going for it is warm sea surface temperatures from the Indian Ocean all the way to the western Pacific. So again, it could be just a matter of time.

It’s definitely interesting to note the latest European Weekly model brings a pattern change during the last 7-10 days of May, bringing a trough to the western U.S. and a ridge to the eastern and southeastern U.S. This would loosely fit the approximate MJO phase 5 timing if it indeed takes perhaps 15 or 20 days to make it that far east.

In a nutshell I think it’s safe to say it’s just a matter of time before the chase season comes back to life! And this shouldn’t really be a surprise. I mean, mother nature cannot just keep the pattern perpetually crappy for the remainder of the season. Something’s gotta give. And that ‘give’ is showing up right now in the form of growing convection over the Indian Ocean. By sometime in late May that convection could cause latent heat feedbacks over the Pacific jet stream that will in turn force a series of strong troughs across the western U.S. and a ridge over the southern and eastern U.S. Finally, this will all combine with deep moisture from the Gulf of Mexico to bring supercells and tornadoes to the Great Plains.

Right…if only it were THAT simple! But the pieces of the puzzle are starting to come together. It’s more than just hope. The data says keep your eyes open and be patient.

It’s just a matter of time….

 

Jim

Apr 282013
 

Sunday, 28 April 2013

 

It must be a combination of a busy work schedule and a slow weather pattern. But whatever the actual reason, somehow time has just flown by and all of a sudden it’s almost May! It feels like just the other day I was writing a post about how my favorite month is actually April, since you still have the whole month of May in front of you. Now here we are and April is almost over.

I mention May with such gusto because it’s the climatological peak in the southern plains tornado season. And most storm chasers are well aware that there are usually good tornado setups during some part of May. That’s why every year hundreds to perhaps over a thousand storm chasers from across the U.S. and from around the world have been waiting for the month of May to begin. Of course the same number or more storm chasers wait until June to take their storm chasing vacation. But that’s the topic for another discussion.

So right now is the time when all the preparation is basically done. Storm chasers have their camera equipment, gps/maps, laptops and vehicles all set for storm chasing. Some plan their trips well in advance, and some wait until the weather pattern is favorable for significant severe weather events until taking their trip. Unfortunately for a lot chasers, especially the ones overseas, taking a chasing trip on the fly isn’t practical. Thus, many chasers have to kinda roll the dice and plan their trip out months in advance. And that’s why a lot of chasers from all over the world choose their storm chasing vacation during the month of May, because it is the climatological peak in the southern plains tornado season. Essentially, they are playing the odds.

So here we are. It’s only a few days before the start of May and the tornado season has been and continues to be very, very slow. Forecasts for the next several days don’t really bring much hope or excitement to the upcoming season. We had a very cold late winter that didn’t want to let go in March. Things quickly turned around in Mid April, but too much of mother nature’s grip from winter held on and the severe weather setups that unfolded had significant issues with both the CAP as well a bit too much cold front involvement. Basically, it just wasn’t meant to be.

Unfortunately, the weather pattern continues to be stubborn. We’ll call it the high latitude blocking ‘hangover effect’ from late winter, but whatever phrase or word you want to use, it just doesn’t want to let go. Not yet. Sorry, not today, and not anytime soon. It’s partly due to the MJO (Madden Julian Oscillation) returning to the wrong side of the northern hemisphere, coupled with a Pacific pattern that favors a ridge over western North America. Any systems that break through the ridge are forced under another blocking ridge over eastern Canada, bringing troughs to the Southeastern U.S. In essence, the pattern we are headed towards over the coming weeks does not look great for active severe weather events or tornadoes across the Great Plains of the U.S. It doesn’t mean nothing will happen, because the atmosphere — even in terrible chase patterns — almost always finds a way to produce supercells and at least a few tornadoes during the month of May. But it certainly appears that mother nature has other things on her mind for May besides tornadoes. Perhaps she’s more interested in drought recovery through heavy rain events instead of supercells and tornadoes? From that angle, things could be much worse.

So where do we go from here? I mean what usually happens when the peak month for tornadoes is, for lack of a better word, a dud? Well in some of the worst years on record the season never really picked up, it just sorta never got going. Sometimes a ridge just expands and summer sets in by June, and there are not many significant severe weather events during the season.

Ok, you can step away from the ledge and relax! Take a deep breath. This year doesn’t seem quite like that, at least not yet. It doesn’t look good, but we’re not to the point where we need to start waiving a white flag or anything like that. There is hope, and it has my full undivided attention.

I’ve been watching the sea surface temperature trends across the Pacific and have found some interesting similarities to recent years. While I don’t think this season is going to be good at all as whole, it’s far too early to write off as a complete dud. We may be headed towards a summer where El Nino tries to develop. Sometimes when this occurs the MJO steps up to the plate and brings a large extension to the Pacific jet stream all the way to North America. It doesn’t happen for very long and it only happens as a sorta transition from the spring to the summer pattern. But when it does occur, it can bring with it a period (a week or two) of significant severe weather outbreaks including tornadoes to the Great Plains and central U.S.

So don’t despair, don’t lose hope. May is upon us. Sure the weather pattern is depressing and forecasts for the next few weeks probably won’t look that encouraging. There will be setups that may not be ideal. But keep hope alive, stay positive. Mother nature is brewing the Pacific just right so that by late May or June, the jet stream will come roaring across the Pacific Ocean towards the west coast and chasers from around the world will get excited. They’ll be rejoicing because their patience has paid off and a series of severe weather events will be poised to unfold across the Great Plains. And they will say to themselves, “This is what I’ve been waiting for. This is what I live for.”

Until next time…

 

Jim

Apr 242013
 

Wednesday, 24 April 2013

 
Click on photo for a larger image

Shelf cloud in Greensburg, PA.

Shelf cloud in Greensburg, PA.


 

Local, on the fly chases are a lot of fun. They are simple and relatively stress-free. And success is pretty much a given since you weren’t really expecting to chase, so you’re expectations from the beginning are near zero. So as long as you see anything cool at all, the day was a success and everything is good!

I left work today knowing there were some pretty weak thunderstorms heading in my direction along the cold front. I was essentially expecting to see a dark sky followed by heavy rain, drive through it and call it a day. Instead, I was greeted by a decent looking shelf cloud — especially for western PA standards for anything forming along a cold front.

 
Click on photo for a larger image

Shelf cloud in Greensburg, PA.

Shelf cloud in Greensburg, PA.


 

Now you’ll have to excuse the foreground buildings such as JCPenney and Best Buy. The only decent shot I had of seeing this shelf cloud at all without numerous obstructions was at the local mall parking lot! And yes, I got numerous stares and finger pointing from shoppers and motorists. I mean seriously, I guy can’t take pictures of a thunderstorm? And by the way, people here drive just as bad in the rain as they do in the snow!

 
Click on photo for a larger image

Shelf cloud and inflow band.

Shelf cloud and inflow band.


 

 
Click on photo for a larger image

You can see the rain shaft on the left and the shelf cloud on the right.

You can see the rain shaft on the left and the shelf cloud on the right.


 

Once this storm moved off to my northeast, I dove south towards another stronger cell. Upon reaching my new target I did see a nice lowered base. Unfortunately with the hills and increasing traffic I wasn’t able to get a clear shot of it before getting hit by the core of the storm. But it was a fun local chase to say the least. And I know it sounds kinda silly to get a kick out of a mediocre shelf cloud. And if this was a chase day in the Great Plains at the peak of tornado season, then yes, I WOULD be disappointed. But I had zero expectations going into this and simply had an enjoyable afternoon documenting a shelf cloud in my local area. No harm in that!

 

Jim

Apr 192013
 

Friday, 19 April 2013

 

The first active severe weather period for April has come and gone. This period, which was Sunday through Thursday of this week (April 14-18), had been poking it’s head above water well in advance. So it seemed likely more than a week in advance that a series of potential severe weather events would unfold across the Great Plains and central U.S. But of course the details were in question, and it’s those details that often times dictate whether or not a severe weather setup will be capable of producing numerous tornadoes.

During the first three setups (Sunday through Tuesday), a strong CAP located near the 850mb pressure level was likely the main reason for the limited to no supercell thunderstorm formation. When supercells did form, they struggled with the CAP. This wasn’t too surprising with the lack of good large scale forcing to cool the mid level temperatures sufficiently. In other words, lift from strong jet stream winds associated with main storm system out west hadn’t quite made it out the plains just yet.

What is interesting is the events from both Wednesday and Thursday both had very similar issues. Wednesday was advertised as a potentially significant severe weather day across Oklahoma and surrounding areas. Supercells indeed fired and sustained themselves all afternoon into the evening across southwestern Oklahoma. But at first glance one should have been scratching their head at the lack of more significant tornado reports from those supercells given the high levels of low level wind shear coupled with ample instability. But once you investigate the mid level temperatures, you see what the problem actually was.

 

Storm reports from April 17, 2013.

Storm reports from April 17, 2013.


 

Below are two soundings from 00z April 18 (7pm local time). The first is from Dallas, Texas. Notice the inversion (warm layer) located around the 675mb level. A CAP located that high in the mid levels causes thunderstorm updrafts to struggle. The 850mb inversion has been eroded, but it’s that warm layer located much higher up that really causes issues with not only thunderstorm updrafts, but consequently the tornado potential with the thunderstorm. You can also see an inversion from the Norman, Oklahoma sounding (despite the sounding data stopping around 675mb) below. This inversion is likely a contributing factor in the lack of more long track tornadoes produced on Wednesday across southwest Oklahoma.

 

Dallas Fort Worth sounding from 7pm April 17, 2013.  Notice the CAP located near the 675mb level.

Dallas Fort Worth sounding from 7pm April 17, 2013. Notice the CAP located near the 675mb level.


 
Norman, Oklahoma sounding from 7pm April 17.  Notice the CAP located near the 800mb level.

Norman, Oklahoma sounding from 7pm April 17. Notice the CAP located near the 800mb level.


 

Going one step further, this same storm system moved into the Midwest and Tennessee valley areas on Thursday. Wind shear and instability were present along with adequate moisture. But one problem was a squall line that never dissipated and continued moving east across Missouri, Illinois and Indiana (see image below). Cloud cover ahead of that squall line was another issue, limiting quality surface heating. But those weren’t even the biggest issues. Discrete storms (including supercells) might have had a chance at forming out ahead of that line of thunderstorms had their not been another high level CAP!

 

Storm reports from April 18, 2013.

Storm reports from April 18, 2013.


 

 

Regional radar image from 6:50pm EDT on April 18 over the Midwest/Ohio Valley region.

Regional radar image from 6:50pm EDT on April 18 over the Midwest/Ohio Valley region.


 

Below is the 00z April 19 (7pm Thursday) sounding from Nashville, Tennessee. Notice the CAP located at 675mb, the same level the inversion was located on the Dallas sounding from the previous day. Also look at the Indianapolis sounding from Thursday morning. While not as pronounced you can still see an inversion near the 675mb layer.

 

Nashville sounding at 7pm on April 18.  Notice the inversion at the 675mb layer, the same level where the inversion was located on the Dallas Fort Worth sounding from the previous day.

Nashville sounding at 7pm on April 18. Notice the inversion at the 675mb layer, the same level where the inversion was located on the Dallas Fort Worth sounding from the previous day.


 
Indianapolis, Indiana sounding from 7am on April 18.  Notice the inversion located at 675mb.

Indianapolis, Indiana sounding from 7am on April 18. Notice the inversion located at 675mb.


 

So what is going on here? I mean, a big storm system moved into the central U.S. during the week. For three days in advance of that system there were severe weather setups that were ultimately destroyed by the CAP. That’s not too unusual, especially early in the season when sometimes low level moisture and especially cloud cover can be a major inhibiting factor. But for both days — when the main storm system was involved — to be completely underperformed due to continued capping inversion issues? This is not good. Either this pattern was trashed from the beginning, or something smells bad as head deeper into the storm chasing season.

IMO the pattern that evolved coming out of the cold March we had was the issue. So over the next couple weeks or so the weather pattern just needs some time to adjust. The atmospheric ‘hangover’ from historic high latitude blocking needs time to disappear, and spring just needs time to be refreshed. We need a do-over. The other issue that hasn’t gone away is the current drought over the plains states. I believe that was probably a contributing factor to the significant CAP we’ve seen as of late. I’m not sure that issue is necessarily going to be resolved without a fight.

Alas we wait ’till May with our fingers crossed…

 

Jim

Apr 152013
 

Monday, 15 April 2013

 

Once again I see you’ve met my friend the CAP. He’s been responsible for preventing more widespread storm chasing setups from occurring across the southern plains states as of late. But for a day like Wednesday, April 17, when enough large scale forcing will be in place to weaken our friend and allow for storms to fire, it’s ironic for so many other complicating factors to come into play. And it may not be as widespread of a severe weather event as some might expect for many other reasons not related to the CAP! In fact, it could be a rather messy setup. Then again, should these issues be resolved, I could absolutely envision tornadic supercells occurring. But one step at a time.

The computer models we use as tools to predict thunderstorms and it turn, tornadoes, are not agreeing on how far north a cold front will retreat as a warm front on Wednesday across Oklahoma. The current options on the table range from central Oklahoma to the Kansas/Nebraska border. On top of that, there is considerable uncertainty regarding the evolution of the convection leftover from Tuesday night’s activity along that front. There will be a lot of moisture, large scale ascent and other dynamics at play all basically having a traffic jam from along the Red River into Oklahoma and Kansas Wednesday morning. I imagine there will be convective debris in the form of messy thunderstorms/rain and low clouds that could linger well into the day. Until we know how all of this will evolve throughout the day on Wednesday, I’m afraid it may be a bit too soon to get excited about the potential for tornadic supercells, at least for now. I think we need a bit more data.

 

12z April 15, 2013 WRF model surface dewpoint forecast for Wednesday, April 17 at 7pm CDT.  Notice deep moisture only reaches to as far north as central Oklahoma and far east Kansas thanks to the cold front remaining over northern Oklahoma and eastern Kansas.

12z April 15, 2013 WRF model surface dewpoint forecast for Wednesday, April 17 at 7pm CDT. Notice deep moisture only reaches to as far north as central Oklahoma and far east Kansas thanks to the cold front remaining over northern Oklahoma and eastern Kansas.


 

 

12z April 15, 2013 GFS surface dewpoint forecast for April 17 at 7pm CDT.  Notice how much further north the deep moisture reaches on this model.  Lower 60s dewpoints reach into northern Kansas because the cold front has lifted north into southern Nebraska.  This is a much different scenario vs. what the WRF model indicates.

12z April 15, 2013 GFS surface dewpoint forecast for Wednesday, April 17 at 7pm CDT. Notice how much further north the deep moisture reaches on this model. Lower 60s dewpoints reach into northern Kansas because the cold front has lifted north into southern Nebraska. This is a much different scenario vs. what the WRF model indicates.


 

If that front can lift far enough north and if the convective debris moves out of the warm sector early enough in the day Wednesday, then we can start talking about much more interesting things! In that scenario (essentially the 00z April 15 2013 run of the WRF model, the GFS depicts moreso the messy scenario despite lifting the front far enough north – gotta love computer models :) ) supercells would likely form off the dryline from western north Texas into Oklahoma and have moderate tornado potential.

But the devil is in the details.

 

Jim

Apr 132013
 

Saturday, 13 April 2013

 

The atmosphere is one finicky beast! This isn’t news to me or anything. Rather, it’s something I’m reminded of anytime a forecast for a period of severe weather doesn’t quite pan out the way I expect it to. Mother nature requires a certain balance between moisture, instability, wind shear and large scale forcing to produce severe weather setups that can then bring storm chasers supercells and tornadoes. But if one piece of the puzzle doesn’t fit quite right, the whole thing falls apart and you end up with one big mess!

So while the large scale weather pattern over the next few days is coming together like I have been anticipating since the late winter, so many of the details are not that the end result may be very disappointing. And yes, the atmosphere is extremely particular about the conditions necessary to bring good storm chasing setups. That statement may be more valid this season than most considering the current drought situation. (Yes, the drought continues over the Great Plains. The CAP has already been a major issue during recent severe weather setups, and it looks like that trend will continue. See images below).

 

U.S. drought monitor as of April 9, 2013.

U.S. drought monitor as of April 9, 2013.


 
Long-term drought indicator created April 6, 2013.

Long-term drought indicator created April 6, 2013.


 

The severe weather setups that will occur Sunday through Wednesday over the Great Plains have a lot working against them. This is especially true for both Sunday and Monday’s setups. Whether it’s forcing along the cold front or a CAP that can’t break due to a lack of large scale lift, neither setup is all that appealing. But once the main trough from out west ejects late Tuesday and finally on Wednesday, I do think there will be a lot more potential. Not only for a more widespread severe weather day, but possibly discrete supercells and tornadoes *IF* the atmosphere – who is one finicky beast – manages to put together all the ingredients in such a way that is acceptable for mother nature.

Unfortunately for this storm chaser, a two day severe weather event three days in the future that still holds considerable uncertainty just isn’t enticing enough to make the long drive out to the plains. And it’s a little disappointing, too. Because the odds are with the available moisture and the strength of that trough (system coming out of the western states) that there will be supercells producing tornadoes on one of those days.

After this series of severe weather setups, mother nature wants to shut down the shop for a while in the form of a ridge over the western U.S. You can thank the tropical convection over by Indonesia, along with other mechanisms, in helping to bring and sustain this ridge for what looks like potentially a few weeks.

Alas, I guess I’ll just have to wait ’till May…

 

- Jim