Sunday, December 23, 2012

Christmas Day mayhem along the Gulf Coast?

I put a question mark in the title, as there's still some uncertainty about how much mayhem there'll be.  That being said, the ingredients are more or less coming together for a severe weather outbreak on Christmas Day in Louisiana, Mississippi, Alabama and the Florida panhandle.

Moisture, instability, shear and trigger will all be there, and I've got the corresponding maps below.  But to summarize: dewpoints will be in the mid to upper teens; MLCAPE will be in excess of 1000 and, in some cases, 2000 J/kg; shear will be plentiful, with deep shear around 50 knots and 0-1 km shear around 30; the triggers will be numerous, including likely seabreeze interactions as well as a cold front.

So, what could happen?

Scenario 1) the warm sector lights up with tornadic supercells
Scenario 2) the warm sector is clagged in with low cloud and fog, eliminating any severe weather threat
Scenario 3) the warm sector is capped, leading to only cold front convection

Scenario 1 seems to be fairly likely right now, although there may be so many storms that they destructively interfere with one another.  Scenario 2 looks unlikely, as for that to happen you need to have a strong inversion due to really warm air aloft (~850 mb) to trap things, and that's not currently forecast.  Scenario 3 also looks unlikely, as there's little cap to speak of forecast.

The most favourable juxtaposition of instability and shear looks to be from about central Louisiana to western Mississippi, with a second area in southern Alabama.  That being said, it appears that the strength of tornadoes may be somewhat mitigated because of what the forecast soundings in the warm sector are showing: modest, at most, low-level instability, usually necessary for strong low-level vertical motion.  As well, low-level turning of the winds isn't tremendous, albeit adequate for tornadic supercells.  If winds can back locally, though, then that'll increase the helicity a lot.

The place where forecast soundings do show stronger low-level instability is in western Louisiana, that being along the cold front.  So if the cold front isn't too aggressive and surface winds can stay backed, the area of strongest storms and highest tornado chances would be here.

Last two things about these storms: they are going to have low cloud bases. As in almost at the ground. So any storms that do form will make it very dark, almost impossible to see what's coming.  Second, a lot of these storms could go well after nightfall.  If, indeed, they do contain tornadoes, this would be the most dangerous time--tornadoes at night are that much more dangerous.

I hope people keep an eye on the weather on the Gulf Coast on Christmas Day.

Thursday, October 25, 2012

Not even a lightning strike

We got to Eau Claire and it was cloudy, drizzly and about 20 degrees.  Close to the warm sector.  After a lunch stop, we decided to drop south to La Crosse, where it turned out to be about 23/18.  Not bad but, unfortunately, too cloudy--and therefore the cap wasn't able to break.

We were, however, able to call the chase relatively early (6 PM) because darkness came on so early.  A silver lining, I suppose, to that cloud.

Tuesday, October 23, 2012

October chase possible? Really?

I'm going to be in Minnesota tomorrow, visiting. The visit is totally unrelated to chasing, but it appears I may have something to chase tomorrow.

No, really, I'm serious.

Here's the setup.

Moisture: it's looking pretty good.  I checked the current obs, and there's already a 64F (18C) dewpoint in northeastern Iowa.  Don't believe me?  Have a look-see.

And by tomorrow afternoon it's forecast to only get better, both at 850 and at the surface.

And as a result, the instability is forecast to be very good.

3000 J/kg?  In October?  I'll take that in June!
How about the upper winds and therefore shear?

Plentiful.  Combine that with good low-level veering and that would give a fairly chaseable storm motion of around 20 knots.

So, what to do?  Here's a prog sounding for the region, around 4 PM.

There are 2 negatives I can see for this case.  First off, it's not the best chasing territory; that part of the world tends to be rather hilly and treed, with not as many navigable, straight roads as in the plains.  Second, it's October, so that means sunset will be around 7 PM--not a huge window of daytime opportunity.

If this setup holds, it looks like we will be going for a target of Eau Claire and watching things develop.  Wish us luck!

Thursday, August 2, 2012

2012 so far

I haven't posted in a long time here--my fault, although I suppose my reader (haha) doesn't check here that much. That said, for me, this year has been a disappointing one. I have had one bad decision and a bunch of bad luck/bad timing events. First the bad luck. This event is one we decided to blow off because, until the afternoon of the day of, it looked highly conditional as to whether the cap would be broken at all. We knew, however, that should a storm go, it would produce. We ended our trip and therefore missed this event. Then it was time to chase with CoD. This time, we were in the right position for every storm that went, but the flow was uncharacteristically slack for the time of year, and storms were mainly multicell stuff. Some storms had a slight chance, but they ended up being outflow-dominant. Then this event with this tornado and this tornado happened in Saskatchewan. I couldn't go because of work, but I knew it would be a good one. My third (long) trip of the year was with my wife. Again, the flow was slack and mainly multicells were the dominant mode. We got some good lightning shots, but storm structure was just lacking. Had we had our trip a week later, we would have caught this along with CoD, who was on their trip 5 of the year. I've been on a couple of spot chases. One storm in northwest North Dakota was outflow-dominant and messy, and a couple in southern Manitoba really had no chance but were marginally-severe hailers. I know that there'll always be more storms, but this year it seems (to me) that I've just got the worst luck. There's still about a month left in the storm season, so there's still hope.

Thursday, May 24, 2012

An actual post about the last chase day

I suppose I ought to post about yesterday's chase. We decided to play the edge of the cap and its intersection with the sagging cold front--said cold front was sagging through Nebraska. We got in place nice and early and sat to play the waiting game. And wait we did. We were pretty close to initiation, too, and when it went, we saw some pretty neat storms. The storm that looked the best was a little to our southwest; it had a ragged, albeit somewhat high-based, wall cloud, and the updraft/downdraft separation was obvious. After a few minutes, a rather interesting dust swirl appeared on the ground, a little offset from being right underneath the wall cloud but not by much. It persisted for a few minutes and moved off, and it was clear by the end of its life that it was a gustnado. A few minutes later, another one formed and behaved much in the same manner. Eventually the storm really started to move (~70 km/h) so we had to take off to keep up with it. Problem was, we had the Missouri River to contend with. There aren't unlimited crossings, so we had to cross it south of the storm's path, as it was going right toward another crossing. The crossing was about 20 miles south of the storm, just far enough that we couldn't see it. While we were turning east to get to the river crossing, we witnessed a close call for an accident. I won't go into the details (no, it didn't involve us) but it just goes to show: the most dangerous part of storm chasing is the driving. Anyhow, we finally got back around to see the storm and it was waging an epic battle between outflow and inflow. It would appear, at various times, to have a huge gust front and then the storm would surge ahead of it and there would be an obvious wall cloud. Anyhow, we chased it (literally) for about 3 hours before giving up, as it was still moving away to us at such a speed that we could barely match, and it was starting to get dark. So we decided to stop, tripod and take lightning pictures. Wouldn't you know it, another storm popped up to our west, and it got severe warned. So after finishing up our lightning pictures, we decided to core punch. I know, I know, I rail against it, but we had good reason to believe that this core wouldn't be all that bad--for one, its RADAR presentation was that it was putting out quarter-sized hail, maybe, and for two, the largest hail that had been reported in the area from any storm was quarter-sized. So we went for it. Once we hit the core, we had to stop. Visibility was zero in heavy rain and small hail (we missed the bigger stuff) and, although I really really suck at estimating wind speeds, I wouldn't be surprised if the winds met the NWS severe criterion. The storm soon passed and we went to the hotel for the night. Not a bad day.

Day the last: retrospective

So we're now on our way back home, after a somewhat anticlimactic trip. This year, aside from a couple of little errors here and there that didn't really cost us, we by and large were in the right place. Too bad we can't say the same thing about moisture. A couple of weeks ago, a cold front smashed through the US and shunted all the deep moisture into the Gulf of Mexico. Since then, a return southerly flow has been reluctant to set up and as a result, the available moisture has been just what was already in place. So instead of May dewpoints in the low 20s, we were looking at may dewpoints in the low teens. Marginal moisture for this time of year. So I'm feeling a little discouraged--not for myself, as I have many more chase days planned this summer, and not for Hobson, because he's going to chase every cumulus cloud for the rest of the summer, but for the other guys who don't get too much of a chance to chase. This would put me off chasing for a while if it were me. I always go back to wxdog's mantra: there'll always be more storms. Man, I hope so.

Wednesday, May 23, 2012

Oh moisture, moisture, wherefore art thou, moisture?

This trip has been marked by a lack of moisture. May is usually moist in the southern and central plains. But a couple of weeks ago a cold front blasted through the states and flushed the moisture out of the region. It's because of this cold front that storms have struggled to get really meaty during this trip. Even the tornadoes that have happened while we were here (that we missed, naturally) have been short-lived. This is just not a scenario I had even considered to be possible in late May here. Anyhow, yesterday we got to our target of Valentine, NE (can't be a chase trip without at least once going through Cherry County) and storms were starting to go. We didn't have a great visual because a) it was pretty hazy and b) there was lots of cirrus overhead. Still, though, RADAR was great help to us. A storm eventually went in our area and was looking pretty good on RADAR, and it even got severe warned. Then we got within viewing distance and, wouldn't you know it, the storm up and died. Like the previous day it wasn't a quick death; it took a few minutes to completely choke off, and it even made one valiant attempt at regeneration. But in the end, it seems the storm killers struck again. There were a couple of silver linings in that cloud, however: first, because we didn't go north, we didn't waste a whole bunch of money and time on storms that were underwhelming; second, we got a couple of good lightning shots. Today is looking not bad, although the orientation of the shear vectors with respect to the forcing isn't all that good. A cold front will be sagging through southern Nebraska and western Iowa, and storms should fire along it. Whether they put out for us is another question, but you never know--mesoscale accidents happen all the time. Or so I hear.

Tuesday, May 22, 2012

Day 3 recap and day 4

So we ended up in New Mexico for lunch, waiting for storms to start in that region. They soon did, with towers going up over the Raton Mesa area. Thing is, they stayed on the rocks for a long long time. They just kept pounding the same area; at one point, the hail markers on GR were over 3 inches. I figure there had to be some flash flooding somewhere in northeast New Mexico yesterday. We sat on Bob's road for a while then, watching and waiting, all the while tossing around the football. Storms then decided to move--slowly, mind you--off the terrain but by this point there were a bunch of them, and it looked like destructive interference was occurring. In addition, we were getting chilly--I had to put on my hoodie. But at one point, a storm just to our northwest seemed to have a good look to it, sort of LP. It didn't look that hot on RADAR, so we made an executive decision to go after towers that were looking pretty healthy to our northeast. We also noted a line of cumuli trying to get interesting well east of the cluster action, in the western Texas panhandle. As we got a little farther east, the towers to the northeast were visually and on RADAR looking increasingly meh. So we decided at that point that we would go to Kansas and call it a night, repositioning for the next day (today). Along the way we were watching an interesting storm all by its lonesome in southwest Kansas. It was clearly a multicell, as the anvil being blown downwind would show a wavelike formation, indicating successive updraft pulses. It gradually began to acquire a backsheared anvil, so we decided to investigate. As we got closer, reports of golf ball hail from the now-warned storm came in, and it looked impressive. But, as seems to happen a lot, the storm decided to stop its production of anything once we got within looking distance; it didn't die as quickly as the storm the previous evening, but it was clearly dying. So we decided to drive along to dinner and bed for the evening whereupon we saw that the line of cumuli in the west Texas panhandle had grown into a beast of a supercell, and tornado reports were coming in from it. D'oh! The hail marker was well over 3 inches, and it had a pretty meaty RADAR presentation, so it looked to me like it was an HP beast with a tornado in there somewhere. It didn't last too long, however, as it was quickly to be overtaken by a pretty impressive squall line that evolved from the cluster we had been on a few hours before. Now onto today. Today looks like a gamble, in a weird kind of way. For a few reasons (don't want to drive crazy amounts, skeptical about moisture) we decided to forgo the risk in the Dakotas (close to home) and chase down the lee trough in Nebraska. A lot of chasers are in the Dakotas today, but it's been my experience that, in these strongly-forced situations, storms go early and in big numbers, while farther down the line, in the more capped environment, a more isolated beast goes up. We're hoping for and banking on that. As always, time will tell.

Monday, May 21, 2012

Day 2 recap and day 3

Yesterday was an interesting day, once again. Then again, I see all storm chase days as interesting. We left the hotel after a good night's sleep and set out with our initial target as Lawton, OK. Along the way we saw that there was a smattering of boundaries out there--some outflow, some a decelerating cold front--just south of Frederick. We thus redefined our target as just south of there in Texas. We got to Texas (first time for 3/5 of us!) and got there just in time for the first set of towers going up. We couldn't see them all that well, though, because there was a lot of low-level grunge around. But a couple of storms got organized around us, and we were in business. Soon the storm to our northwest got pretty powerful and the hail marker on GR was showing over 3 inches, which is usually a sign that a storm is making at least golf ball-sized ice cubes. Anyhow, the storm was struggling to stay in the warm air, as it had formed on the boundary but was being overtaken by it, so it was at times looking good and at times looking no so good. We were wondering if this storm was going to do anything when, farther west in better air, a storm rocketed up near Guthrie, TX. Because of the better moisture in place and the lack of destructive interference going on, we made the snap decision to go to that one. It soon looked rather impressive on RADAR, and we knew we had made the right call. Then the NWS dropped the severe thunderstorm warning on the storm. We then questioned our earlier decision, but the storms we had left were looking worse and worse, both visually and on RADAR. So we pressed on, and soon enough the warning was re-issued for the storm. We got close to it and it looked not bad, a sort of LP-type storm with a fairly tilted updraft and obvious hail core. Speaking of which, tennis ball-sized hail got reported with this storm south of Guthrie, so we knew it was a pretty good one.
Then one thing Justin and I had seen once before happened: pretty much right before our eyes, the storm evaporated. Poof, pretty much gone from great storm to nothing in about 20 minutes. Pretty impressive. We knew we were done for the day and therefore took off for our hotel in Childress, TX. Along the way, though, we had to stop to watch the eclipse which, if it wasn't total where we were, it was close. Justin got video of it which he tells me he will post at some point. Anyway, the eclipse was way cooler than I had ever imagined, and I think it was enhanced by the fact that it was low on the horizon and therefore we got an eclipse of the setting sun. All red and beautiful. I now see why people pay huge amounts of money to see eclipses.
A good day, and a bonus eclipse! **As I was writing this we got pulled over for speeding. The talk in the van unfortunately made us miss a slower speed limit sign, and we were caught going well over the speed limit. However, the policeman was pretty cool about it, first asking us where Manitoba is. He let us off with a warning. So to the anonymous policeman in Estelline, TX, thank you.**

Sunday, May 20, 2012

Day 2 in OK and TX

Looks like we're going to be playing in Oklahoma and Texas today, from Lawton OK to Wichita Falls, TX to Childress, TX. Its a fairly marginal day, with all right CAPEs and marginal shear, but it's something to look at. Still, though, the way the setup is, there could be some fairly loopy hodographs. My main concern is that there's little capping so things could end up being pretty messy and multicellular. That being said, we can't rule out a mesoscale accident, as happened west of Wichita yesterday afternoon. A number of pretty tornadoes happened around there, and the shear was pretty crappy. So time will tell...

Saturday, May 19, 2012

Day 1: better than it ought to have been

We caught some neat storms today, and I would submit that it was worth the lack of sleep and driving all day. We essentially got to areas southwest of Omaha and caught a supercell that gave us some hope and wall clouds. At times it looked like it would produce, as it was sucking air in pretty consistently at an estimated 25 knots. And just when we thought it was over, another burst of air ingestion would occur, making it look like it was about to produce. Given the relatively low dewpoints, I suppose we couldn't expect tornadoes, but it's nice to hope.

On the road

We got on the road at a ridiculously early hour, 4 AM. This after I had just come back from a week-long work trip 4 hours before. Apparently we're hardcore. Anyhow, we're targeting, at least initially, Omaha, NE, where modest moisture and good flow should combine to produce some nice storms. There were some bumps along the way, specifically with regard to data, but my wife fixed those problems for us (thanks, sweetie!) and we are no longer running blind. If you want to follow along on Twitter, we're likely to have more up-to-date bite-sized nuggets of observations. Follow me @StormStructure, Hobson @justinhobson85, or Chris @CKStamms.

Thursday, May 17, 2012

Chase forecast, May 17 evening version

Sorry, folks, no imagery today. Go look it up for yourself, if you're so inclined. So it appears I may lose the bet I made with Hobson yesterday, and that's just fine. If that happens, it means our chase will have better moisture than has been in the region recently. If storms do go, though, they'll likely be organized, possibly supercells, albeit high-based. I suppose going chasing to work out the kinks will be beneficial. Or perhaps I'm just trying to make myself feel better because I can't go. Saturday looks pretty good, although still somewhat lacking in terms of moisture. But a surface low west of Omaha coupled with the approach of a compact short-wave trough will likely lead to some rather good storms in the Omaha region. Sunday has some storm potential, but I don't know how realistic it is to chase them--they will likely be in the Texas panhandle. The drive from Omaha to Amarillo is on the order of 11 hours. Yeah. Monday is when the return flow really starts to get going. The Gulf is forecast to open up. Finally. Nebraska or Colorado for a northwest flow setup. Tuesday looks like the day before the day in Nebraska. Wednesday--this is still looking like a big day. Back to eastern Nebraska, at least with this run. Thursday looks uncertain, but perhaps Iowa will work out. A few more days of chasing could occur, although I don't trust the models much at this time in the future. That being said, the central plains could see some action in a week and a half.

Wednesday, May 16, 2012

A new year, a new chase

So I suppose it's about time I blogged here, detailing the travels and travails of this year. This year, we're heading out on a trip that will last up to 10 days (much likely fewer than 10 days) in search of the rotating atmosppheric violence for which so many of us clamour. Okay, after that lame attempt at prose even I'm ready to punch myself in the face. But still. We start out on Saturday. This is out of necessity due to scheduling made well in advance, but it looks like it could end up working for us. Friday (May 18) looks marginal, at best, as although moisture and, as a result, CAPE, are progged to be good over the northern plains and southern Red River Valley (of the north, or "the *real* Red River Valley, as an SPC forecaster friend of mine calls it), the NAM and GFS have been consistently painting dewpoints way higher over the continental US than reality has shown. As it sits right now, as I type this, dewpoints (hereafter called "dews") are struggling to get into the double digits (C) in Kansas. KANSAS! So any return of moisture would have to encompass a) an open Gulf of Mexico and b) a strong low-level jet (LLJ). So to begin, let's look at those: the LLJ and moisture. I present to you the NAM 48-hour forecast of dewpoint and wind at 850 mb and the surface. Note that a) the Gulf seems to be open and b) there are 2 distinct areas of moisture, one in the northern plains and one stretching as far north as Kansas. I posit that the area of moisture as far north as Kansas is the *real* return flow, and won't make it in time for convection to be more robust farther north. I will also admit, though, that I have a bet with Justin right now that the dews won't reach 15°C anywhere in Manitoba on Friday. I hope to win said bet.
Anyhow, to beat the hell out of this dead horse, I think that moisture is overdone, badly, so I doubt there will be any major league severe in the region Friday. Now onto Saturday. The beginning of our chase. I feel almost that I should make a "ta-da" sound, or at least make the Imperial Margarine crown appear. But you won't get it; I'm just that kind of guy. Anyhow, we're looking at departing from Winnipeg and trying to make it to the zone of terror. In this case, it appears the farther south, the better. Keeping in mind the craptacularity of moisture being handled in the NAM, we will cautiously look at the trough/convergence line stretching from the progged low in northwest Ontario to the other one in the northeast Texas panhandle. Flow should be not too bad at midlevels, with winds on the order of 30 to 40 knots from the southwest, juxtaposed (I like that word!) with surface winds out of the south.
The NAM does make a convective signal happen, with showers and thunderstorms between Dodge City and Wichita, KS by 3Z on Sunday morning. Is this real? Beats the hell out of me, but with the prog sounding and wind profile, it sure looks promising.
Here's a problem, though: have you ever tried to drive from Winnipeg to even Kansas City? It takes a few (read: MANY) hours. So that's an unrealistic target. So Saturday may, by necessity, end up being a positioning day for us, all while watching storms go up and nothing we can do about it. We may, however, be able to catch something, say, close to Omaha, where similar instability but not-so-backed winds are progged. That's at least a realistic chance.
The 17/00Z GFS, for what it's worth, produces better conditions farther north than does the NAM. We will see, but it appears we will only be able to chase this stuff, if anything at all. Sunday looks only okay at this point. It appears that the trough causing all the awesomeness on Saturday will move east Sunday, leaving only some places for storms, the best of which appears (at this time) to be northeast Oklahoma. The wind fields, however, aren't forecast to be great--multicell, if maybe marginal supercell. Monday looks like a returning flow day in north Texas (Wichita Falls?) or maybe on the caprock. Tuesday looks pretty good for the western plains, be it Nebraska, the Black Hills or western North Dakota. If I had a better confidence in moisture I would be jumping up and down about this day. The good thing I see is stronger winds on the west side of the upper trough, which leads us to... Wednesday is a damn fine day, if the GFS is to be believed. The *digging trough* (referenced above) will cause lee cyclogenesis out over the plains, and the response should be good. This will be a forecast based on convection, if any, the previous night and its resultant outflow, juxtaposed with the good (50 knot) midlevel flow. After this point, I feel it's a losing battle to even try, but I will say this: a week ago, the GFS had a death ridge over the area of interest, and at this time, for the same time period, now it does not. Anyhow, let the season begin It's about time.