Archive for Plains

Finally! El Nino is Bringing Extreme Weather to the U.S.

Posted in Severe weather, Winter weather with tags , , , , , , , , , , , , , , , , , on January 24, 2010 by stormstream

It’s taken half the winter to get here, but finally the low end strong El Nino weather pattern is bearing some major fruit in the U.S. in the form of extreme weather, and this active pattern looks to continue at least through the month of February, and very likely into the spring as well. Get ready for a continued wild ride on the Extreme Weather Express!

The jet stream is powerful and infused with moisture. This has led to many feet of snow across the mountains of California and the Southwest, and severe thunderstorms and tornadoes across the South. Now, we are once again heading into a period where the AO is severely negative, the NAO is negative and PNA is positive. This all equals major DOO DOO for much of the U.S. as we head into late January and through the month of February, but the most extreme weather will likely shift from the western U.S. into the central and eastern U.S. More severe thunderstorms and tornadoes will be possible in the Deep South, with major snow storms north of the heavy rain and severe storms. Also, serious intrusions of bitterly cold arctic air will be dropping into the lower 48 on a regular basis.

Anyone hoping for an early spring with an extended period of sunshine and mild to warm temperatures can kiss those hopes goodbye through at least mid-March, and I don’t care what that glorified rodent The Groundhog says in early February.

Sunday Morning Thoughts on Sunday and Monday Severe Thunderstorm Chances in Kasnas

Posted in Severe weather with tags , , , , , , , , , , , , , on March 22, 2009 by stormstream

No big changes in my thinking.  So far very consistent, which is good.

I won’t beat a dead horse, so all I’ll say about today is if the cap can be breached there could be a classic “no-risk surprise” along the dryline in western Kansas today.  If anyone is free and does not have much to do today, then it would probably be worth a stab.  You really have nothing to lose except time and a little money.

The speeding up trend for Monday has stopped, and the CAPE is trending ever so slowly upward in recent models.  This is great news.  I think the models have finally landed on a solution.  Initiation looks to be between 3pm and 5pm along a line from Larned to Medicine Lodge.  The storms will then move rapidly northeast at 50mph.  Try to be on the storms early, and be wary of their fast speeds and chase accordingly by attacking them aggressively from a downwind position and not find yourself chasing to catch them from behind.

I still have major concerns about the shallow nature of the moisture.  The sounding from Wichita for early tomorrow evening shows the atmosphere drying fairly steadily from just above the surface right on through the atmospheric column.  This could make it tough to get robust convection going, at least robust enough to producd the kind of updrafts and downdrafts you need for tornadoes.  Still, hail and lightning would be good bets in this kind of dry atmospheric environment.  If there is to be a “bust factor” for tomorrow, it will be the shallow nature of the low level moisture.

Also, there may be some showers arond Monday morning and cloudiness may hold pretty tough through a good part of the day.  In these kind of marginal set-ups it is critical that you get good surface heating to help things along.  Keep an eye out on the visible satellite and hope for some good sunshine to get things cooking west of Wichita starting around 11am.  If clouds hold along the dryline through 2pm, then that will not be good.

Severe Weather Continuing to Look Likely for the Plains on March 22 and 23

Posted in Severe weather with tags , , , , , , , , , , , , , , on March 20, 2009 by stormstream

Both Sunday and Monday continue to look like possible severe weather and storm chase days in the Plains, and the storm chase team is on stand-by and ready for action.

On both days the major negative factor for severe weather will be the shallow depth and quality of the modified Gulf of Mexico air that will be reside within the warm sector.  We are talking about dewpoints that will mainly be in the 50s and will struggle mightily to reach the lower 60s near the Red River.  This moisture will also be shallow and lead to a good deal of the moisture being mixed out of the lower atmosphere with afternoon sunshine and heating, thus limiting instability.  If there is to be a bust on Sunday, and the potentially bigger day on Monday, then this will likely be the culprit.

Still, there is decent hope for severe thunderstorms, and even a few tornadoes, and that hope resides with good upper level conditions that will overspread the region late Sunday and especially Monday, a sharp and bulging dryline, and more-than-adequate shear for rotating supercell thunderstorms.  These factors alone make Sunday and Monday both days that any respectable storm chaser needs to mark on their calendars as chase days.  This time of year anything you get is a bonus, so why not?

Sunday is an interesting day.  I’m sure there will be a good number of storm chasers that decide to stay home on Sunday due to the upper support being well to the west, and the rather meager and shallow moisture.  Still, the shear wil be good, and EHI values off the 12z NAM are pushing around 1 across northwest Kansas.  A subtle disturbance crossing the dryline Sunday afternoon could be the trigger to get storms going along the dryline.  If instability were to be just a little stronger than forecast, then a landspout or two might be possible.  The cap will also be pretty strong across Northwest Kansas, so any storms that do develop will be discrete with good visibility.  To me, this definitely looks like one of those potential “sleeper events” where later Sunday evening there could be a few chasers kicking themselves for at least not taking a stab at it when they had the chance.  So, it is definitely something to monitor as we head into Saturday and have better data to analyze the possibility.

On Monday, the upper level conditions improve greatly, but as I stated above, moisture concerns will be present, as will pitential cap concerns.  I’d say that anywhere along the dryline from west-central and central KS, southward into western and central OK and northwest and northern TX would be the zone where supercells and a few tornadoes would be possible.  I would love for dewpoints to reach into the 60-65 range across the northwest OK and KS portion of the target, and for moisture depth to be greater, but with wind trajectories coming out of the central and western Gulf that has been modified by wintertime arctic airmasses, I just do not see that happening.  We really need a fetch out of the Caribbean with these dynamic early season systems to really get them cranking into the major outbreak realm, and that’s not going to happen this go around.  Still, given the magnitude of shear and modest instability with a CAPE between 1,000 and 1,400 j/kg, and the good upper level environment, severe thunderstorms will be likely with the mode being supercells with a threat for a few tornadoes.  The EHI bullseye off of today’s 12z NAM from Medicine Lodge, KS into northwest OK sure looks like a sexy target zone to me at this juncture.  However, we are still a couple of days away from this event so this target is sure to change a bit.

After an Extended Quiet Period, Severe Weather Possibilities Return to the Plains and Missouri Valley March 22-24

Posted in Severe weather with tags , , , , , , , , , , , , , , , , , , on March 18, 2009 by stormstream

The overall weather pattern in the middle part of the country looks to become one that is more conducive to the formation of severe thunderstorms by late this weekend and early next week.

A significant trough of low pressure moves into the Rockies late in the weekend and progresses eastward next Monday and Tuesday.  This will provide the upper level support needed for the possible development of severe storms.  However, the surface will be a little slower to come around.  On Sunday, a dryline will be established in the High Plains, but there will still be significant surface high pressure ridging across all, but the extreme western Gulf of Mexico.  This will effectively limit the return of significant, deep surface moisture on Sunday.  So, we end up with the prospect for some high-based thunderstorms.  Still, shear will be decent, so we will need to watch the moisture and if it ends up being a little more than I think right now, we’ll have to entertain the possibility of a landspout or two.  This has been the case a couple of times this season already, as the atmosphere has had the ability this year in the Plains to overachieve on quite marginal days.  So, Sunday is definitely in play in terms of being a potential storm chase day.

Monday, however, looks much better.  The central and western Gulf of Mexico opens up as the ridging moves east.  There should be a healthy flow of richer surface moisture for about 12 hours begining Sunday night and continuing through Monday.  Still, this will not be the favored Caribbean trajectory that tends to lead to major severe weather outbreaks in Tornado Alley, but moisture should still be adequate for a significant severe weather event given the favorable shear and upper level support.  Nebraska, Kansas, Oklahoma and Texas are in play in terms of severe thunderstorms with large hail, damaging winds, and a few tornadoes.  One thing that will need to be watched, and could impact the southern extent of the threat, will be the elevated mixed layer (EML) or cap.  I think that capping is going to be an issue with most system this spring, but details will not be resoved on this until the actual day of the event.

On Tuesday, March 24th, the focus for severe weather will be shifting eastward into IA, MO, IL, IN, AR, LA and eastern TX.  The best upper support lifts northeast, away from the best instability.  However, I think enough instability and shear will remain to promote severe thunderstorm development from the MO Valley into the Arklatex region.  This day as well appears to be a chase day for local chasers in that region, however, it is not something that I think many Plains chasers would follow unless they totally busted on Monday.

It must be cautioned that as of the writing of this blog entry, we are still four to five days away from this possible severe weather event.  Timing of the system could be off by a day either way. 

I will certainly be keeping a close eye on this, and posting on it regularly in the coming days.

Seven Tornadoes in my Storm Chase Target on a Marginal Day.

Posted in Severe weather with tags , , , , , , , , , , , , on March 8, 2009 by stormstream

The Storm Prediction Center (SPC) is reporting a total of seven tornadoes on Saturday in Reno, Harper and Barber counties in Kansas.  The chase team I’m forecasting and nowcasting for again this season, the team of Jim Reed http://www.jimreedphoto.com/ and Robin Lorenson http://www.robinlorensonphoto.com/, captured video of a tornado near Hutchinson, KS, that aired last night on The Weather Channel.

An early observation about the Plains tornado season so far is that it is an overachieving season.  By that I mean that even on days where moisture and instability are marginal, we are still getting tornadoes forming.  This is key information to know as we head into te meat of the Plains severe weather season, because it means one should probably chase even if it appears on paper conditions just aren’t right for tornadoes.  We had the same kind of season here in the Southeast last year.

I was watching several live video streams yesterday on http://www.severestudios.com/ and they looked fantastic.  This is such a valuable tool for forecasters, nowcasters and emergency managers to be able to actually see what the storms look like on radar and in the field in real time.  For those of us forecasters with chasing experience, we can look at the live stream and radar image and immediately assess the danger and the potential of the storm to intensify further or weaken.  Plus, it let’s us see what we’re missing!

Minor Severe Weather Threat Saturday for Kansas, Oklahoma and Texas

Posted in Severe weather with tags , , , , , , , , , , on March 6, 2009 by stormstream

Saturday will feature some threat of severe thunderstorms extending from central and eastern Kansas, southward across central and eastern Oklahoma and into north Texas.

Moisture will be rather limited, and there will be a strong cap in place across much of the region that will keep severe storm development at bay until the late afternoon and evening hours.

If I were chasing, I’d target the triple point where the dryline intersects the surface low pressure system.  This appears like it will be somewhere west or northwest of Wichita by mid to late afternoon Saturday.

The shear is definitely adequate enough to produce supercells.  So, if storm can get going before dark, early season chasers may be treated to some high based supercells with some decent structure.

Overall, not the most exciting storm day, but one that is probably worth a shot if you live in the area.  Definitely not something to drive hundreds of miles for though.

Tornadoes Possible in Oklahoma and Texas Late This Afternoon and Evening

Posted in Extreme Weather Video, Severe weather with tags , , , , , , , , , , , , , , , on February 10, 2009 by stormstream

The first widespread severe weather event of the 2009 U.S. severe weather season is unfolding, and it looks to be a dangerous situation for some.

Scattered supercell thunderstorms with possible tornadoes will erupt late this afternoon and evening across central and eastern Oklahoma into north Texas. These storms will move quickly east and northeast and eventually form into a squall line of severe storms that produces a lot of damaging wind across Missouri, Arkansas and parts of Louisiana into early Wednesday morning.

On Wednesday and Wednesday night, the conditions are becoming more favorable for severe storms across the Southeast that could not only produce damaging wind, but also some tornadoes. The line of storms that rolls into the region from the west will weaken, but then re-form and re-intensify Wedednesday afternoon and evening. These storms will not only be line segments, but also more discrete supercells with a threat for tornadoes and damaging winds.

Everyone from the eastern Plains eastward across the MO, MS, TN and OH Valley and Southeast, should pay especially close attention to the weather forecast today through Wednesday night, and be ready to take appropriate action should severe weather threaten.