The Day Before Groundhog Day: Yet Another Winter Storm–and More on the Way

Today is February 1, and let's just say it: This winter is getting reeeaaaally old. Incursion after incursion of Arctic air. Snow, snow, snow. Cold, cold, cold--and I do mean cold. After Monday and Tuesday's bitter, subzero bite, these mid-twenties temperatures that have moved in feel practically tropical. Winter_Storm_02012014We're presently under a winter weather advisory, with 3 to 5 inches of snow forecast through 10:00 p.m. around here and an inch more to the south and southeast along the I-94 corridor. And it's wet snow--not as bad as initially expected, according to the latest KGRR forecast discussion, but still watery enough--and therefore heavy enough--to put added stress on flat roofs. Here's a radar image from a few scans back. Look at all that gray! I hardly ever see returns that hit 40 dBZ with a winter storm, but a bit of interrogation revealed 49.5 dBZ over US-131 with this particular scan. And it appears to be all snow too, not a wintry mix. So yeah, I'd call that wet snow. Snow Depth Feb 1 2014The thing is, this stuff just keeps coming. We all know that by now. I haven't seen a winter this snowy since 2009, maybe even before that, since . . . since . . . well, I don't know when. As you can see from today's snow depth map, there's a strip running through my area along the western side of Michigan where the snow depth reportedly exceeds 20 inches. We're not talking about how much snow has actually fallen this winter, just how much of it is presently sitting on the ground. Twenty inches. I can testify that around here, it's not hard to find places where it's nearly up to my knees. Heck, just along the sidewalk outside my apartment, the snowblower has neatly carved a minor canyon along the edge of the featureless white expanse which, if my memory is accurate, used to be what is called a "lawn." Feb 1 GFS 132-hr fcstHow about one more image? Look and groan, because all this glorious wintry nastiness doesn't look to be retreating anytime soon. You're looking at the 132-hour forecast for the surface temperature. Doesn't that look inviting, so full of hope and promise? Tomorrow is Groundhog Day, and I'm telling you right now, that little cretin had better not show his face anywhere in my vicinity or I will send him into permanent hibernation. If there's one good thing about this winter from a personal perspective, it's that it has inspired me to learn about winter forecasting. There's certainly every opportunity to do so, and plenty of incentive. So I've learned a few new terms. Try this one on for size: heterogeneous nucleation. I like that one. Or how about this: DGZ, which stands for dendritic growth zone, the temperature range between -12 and -18 degrees Celsius wherein a saturated layer produces snowflakes. Got that? I'm starting to, along with a deeper appreciation for my RAOB software program. But I'd still be glad to see all this snow and cold go bye-bye, and I'll bet I'm not the only one. Well, well . . . buck up, ladies and gentlemen: meteorological spring is on the way. I just have a hunch it won't be here March 1. It's arrival time may be delayed by snow. What about you? Are you a winter lover or a winter Grinch--or has this winter turned you from one into the other? How do you think this crazy-cold, uber-snowy weather might affect the spring storm season? Drop a comment and share your thoughts.

Are the Great Plains About to Open for Business?

ECMF-GFS H5 fcst 0408013Last year's abnormally balmy March opened for storm chasers with a lion-like roar on the 2nd with a deadly outbreak of tornadoes along the Ohio River southward. But from then on, with the exception of April 13 and 14, the season dwindled into a pathetic, lamb-like bleat. This March has been the polar opposite, and I do mean polar. Many chasers have been champing at the bit due to a wintry pattern that has simply refused to let go. But that may finally be about to change, and April may be the month when this year's chase season starts to howl. For the last several days, I've been eyeballing a large trough on the GFS that wants to invade the Great Plains around April 8, shuttling in Gulf moisture and also suggesting the possibility of warm-front action farther east on the 9th. GFS H5 fcst 00z 040913The ECMWF broadly agrees. The first map (click to enlarge), initialized today at 00Z, compares the 168 hour forecasts for GFS and Euro heights for Sunday evening, April 7 (00Z April 8). The second map, from TwisterData, depicts the GFS 24 hours later at 7 p.m. CST. Maybe not a poster child for negative tilting (though the 6Z run changes that), but it could signal the breaking of the Champagne bottle against the hull of chase season 2013. The details will fill themselves in as the forecast hour narrows down. Right now, this is a hopeful sign for storm chasers. Winter may still have a gasp or two left, but we've made it through, and change is on the way. Prior to that, the models point to a shortwave moving through the upper Midwest next weekend. Will it have sufficient moisture and instability to work with near the warm front? Good question; we'll find out, assuming subsequent model runs don't wash it out. So far it has shown up consistently. For those of us who live northeast of Tornado Alley, it's worth keeping an eye on.  

The Foibles of Long-Range Forecast Models

Tues_March_19_GFS300hrsSometimes a picture really is worth a whole lot of words. In this case, two tell the story more eloquently than I can. In the image to your left, the 12Z run of the  GFS depicts 500 mb height contours, surface moisture, and surface winds at 300 hours out, or twelve days before the forecast date. The second image, taken just a little while ago, shows the same information for the same system, only now we're down to just 66 hours from forecast time. Note that the forecast date has moved up a day to Monday; by Tuesday, the whole system has moved off to the east and out to sea. Bye-bye moisture and instability. Mon_March_18_GFS66hrsWhat happened? The GFS happened, that's what. I realize that for many of my storm chasing readers, maybe most of you, I'm preaching to the choir, but some may wish to take note of the following: Long-range forecast models are notoriously undependable and prone to change. If you've never heard the colloquialism wish-casting, now's the time to add it to your storm chasing lexicon. The further out you go beyond three days from an event, the more that attempting to forecast a chaseable setup amounts to just a hope and a prayer. Bad data and changing data amplify progressively in the numerical models, to the point where what you see at 240 hours out is subject to anything from mild to wild fluctuation and revision as the forecast hour draws closer and new data gets processed. By the time the NAM and SREF lean in, and finally the RAP and HRRR, what you see may resemble nothing like the deep, negatively tilted trough and gorgeous moisture plume that first captured your attention. The shape, the timing, wind speed and direction at different heights, quality of moisture, instability--everything can change, and it will, possibly quite drastically. Remember the gossip chain? Anna tells Peter, "Selena just bought a used Nissan from the same car dealer where Jaden bought his truck. It's on 44th Street about a mile from the dump." Peter passes the news on to Sam thus: "Selena just bought a car from the same dealer where Jaden got his truck next to the 44th Street dump." Sam tells Chelsea, and Chelsea tells Adam, and so it goes, with the information getting nuanced a little more each time until it becomes outright twisted. Finally, word gets back to Selena: "Hey, Selena, what's this I hear about you buying the dump over on 44th Street from some drug dealer?" It can be kind of that way with long-range forecasts. So why even bother watching the long-range models, particularly the famously untrustworthy GFS? There are two reasons. One is, the models can provide a heads-up to the possibility of a chaseworthy setup. At 192 hours out, don't think of the models as forecasts--think of them as potential forecasts, something to keep an eye on. A given scenario could fall completely apart and often does. But it could also develop run-to-run consistency that agrees with the short-range models as they enter the picture, and ultimately lead to a decent chase. For those of us who have to drive a long distance to Tornado Alley, such advance awareness is particularly valuable. If you live in Chickasha, Oklahoma, or Wichita, Kansas, you can roll out of bed in the morning, look at the satellite, surface obs, NAM, and RAP, and decide whether you're going to chase in the afternoon. But if you live in Grand Rapids, Michigan, or Punxatawney, Pennsylvania, things aren't that easy. When you've got to travel 800 to 1,000 miles or more to get to the action, burning time and fuel and perhaps vacation days, lead-time becomes important, and the more, the better. The second reason for watching the long-range models is sheer obsessiveness. Call it desperation if you wish. It has been a long winter and storm chasers are itching to hit the road. Some of us just can't help ourselves--we want to see some flicker of life, some sign of hope, some indication of the Gulf conveyor opening for business beneath a warming sun and dangerous dynamics. What's the harm in that? Most of us know enough not to hang our hats on a 120-hour forecast, let alone one that's two weeks out. But it doesn't hurt to dream. After all, sometimes dreams come true.

Enter March: No Repeat of 2012

March 2 2013 GFSMarch 2013 won't be making anything like last year's brutal grand entry. For residents of the Ohio valley, that is a good thing. On March 2 a year ago, unseasonably springlike conditions fostered an outbreak of tornadoes, including the violent Henryville, Indiana, tornado that my friend Bill Oosterbaan and I intercepted north of Palmyra. This March's arrival portends nothing like that. One look at the map (click to enlarge) will show you that conditions are quite different from last year. The model is today's (February 27, 2013) 00Z run showing the 500 mb heights and surface temperatures for March 2 at 21Z. With a ridge dominating the western half of the CONUS and cold Canadian air sitting atop the Great Lakes, the picture doesn't even remotely resemble the 2012 scenario that sent storm chasers scrambling for their gear. A few days prior to the event--that is, right about now--we were casting anxious eyes on the embryonic system with the sense that northern Dixie Alley was in for it. I'm frankly glad that a cooler, more quiescent opener is in store for the 2013 meteorological spring. I will be pleased to get more snow, and I hope the Midwest and Great Plains get a few more good, solid dumpings before storm season arrives in earnest. Storm chasing aside, the more moisture, the better for regions that have languished under severe drought. As inconvenient as the recent blizzard was for west Texas, I'll bet the folks in Amarillo were mighty glad to get that much snow. I hope they get more, or just water in abundance in whatever form it takes. This March may be entering on the cold side, at least here in Michigan, but that's okay. It is March, the month of transition. I'm equipped with a "new" used car, a 2002 Toyota Camry that is drum tight and ready to take me wherever I need to go in order to see tornadoes. It won't be long now. See y'all under the meso!

Gulf of Mexico Sea Surface Temperatures and the 2013 Storm Season

Every year, the same question inevitably comes up: What is the upcoming tornado season going to be like? The only truly definitive answer is no definitive answer. No one knows for sure till spring arrives, and the best any of us can go by are guesses, some better informed than others. I'm prepared to offer a few thoughts on the matter, but that's all they are: thoughts, sheer speculation, items for consideration, not convictions or predictions; and they are those of a layman, not a professional meteorologist or a climatology expert. With that caveat clearly stated,  I have some hopes that this year will offer a few more "big" chase opportunities than 2012. True, the horrible drought that put the kibosh on setups last year after April 14 hasn't gone away, nor does it show any sign of letup. And without any evaporative boost from moist earth or vegetation, dewpoints are apt to mix out in the Great Plains. That's no news to anyone. ENSO 2013 SST Forecast MapsHowever, I have noticed that sea surface temperatures in the Gulf of Mexico are above normal, and the CPC's (Climate Prediction Center) ENSO maps forecast them to remain so. Below are the most recent maps, current as of January 28,  covering the period from February through June, 2013. Click on the image to enlarge it. At the top right, you'll see the Gulf of Mexico shaded in orange, indicating an average temperature deviation of 0.5 to 1.0 degree Celsius above normal closer to shore, and normal farther out. These are coarse approximations, of course. But you can drill down a little further by checking out current buoy observations against average station temperatures, courtesy of the NODC (National Oceanographic Data Center). Below is their table showing current station obs for February 3 to the far left; and, extending to the right of the obs from some of the stations, average normal monthly temperatures.* A quick glance will tell you that SSTs were well above average for this date, and in light of the ENSO maps, it seems reasonable to think that they will remain so. In fact, today's and yesterday's readings seem to be about a month ahead of the game, though granted, those are just two days, and there are bound to be plenty of  fluctuations through the rest of the month. NODC Current and Avg SSTs What I feel safe in saying is that the overall higher SSTs in the Gulf of Mexico suggest a better moisture fetch than last year's generally anemic return flow. Maybe the Midwest will benefit most from it, and I for one won't weep if there are some decent setups closer to home. I can't think of a better place to chase storms than the flatlands of Illinois. However, it seems to me that Tornado Alley also stands a better chance of action as well, provided the polar jet cooperates this year by showing up farther south, where richer incursions of moisture can get at the energy. Neutral conditions that favor neither El Nino nor La Nina this spring strike me as more promising than last year's La Nina. I weigh the above information against recent (i.e. January 29) CPC drought maps, which don't paint the rosiest of pictures for most of the Great Plains but look good farther east and in the northern plains. Below is the most current drought monitor maps, released January 29; and the drought outlook, valid from January 17 through April 30. CPC Drought Info 1-29-13 Again, I'm neither a climatologist nor a meteorologist, just someone who likes to piece information together and see whether it bears out. Maybe it won't. My original hunch was that, because of the drought, our storm season would be a repeat of last year's, starting early and dying young. And maybe that's the way it will be. But if I correctly understand the implications of warmer-than-normal GOM temperatures, it seems to me that this year could be at least modestly more active than last year's abysmal storm season and might even hold a few surprises. It certainly can't get any worse. _______________ * Station observations shown are for the western Gulf. Obs for the eastern Gulf are also available at the NODC site.

Christmas Day Severe Weather and Tornadoes in Dixie Alley

I hadn't planned to post today, but with the severe weather that the NWS has been forecasting for several days now already underway in east Texas and conditions ripening across southern Dixie Alley from lower Louisiana into Alabama, I thought I'd pin a few of today's 12Z NAM forecast soundings to the wall to let you see what the squawk is about. I'm focusing on Louisiana because it seems to me that, from a storm chasing perspective, that's where the best chances are for daylight viewing--not that I think there will be a whole lot of people chasing down in the woods and swamps on Christmas, but I need some kind of focus for this large and rapidly evolving event. Remember, the sun sets early this time of year. To summarize the situation, a vigorous trough is digging through the South, overlaying the moist sector ahead of an advancing cold front with diffluence across Louisiana, Mississippi, and Alabama. Shear and helicity are more than adequate for supercells and strong tornadoes, with forecast winds in excess of 100 knots at 300 millibars, 80 at 500, and 45-50 at 850, ramping up to 60 at night per the Baton Rouge NAM. I'll start with three soundings in southwest Louisiana at Lake Charles. It's obviously a potent-looking skew-T and hodograph, with over 1,600 J/kg SBCAPE and more-than-ample helicity. No need for me to go into detail as I've displayed parameters that should be self-explanatory; just click on the image and look at the table beneath the hodograph. What I do find noteworthy is the very moist nature of this sounding, suggestive of overall cloudy conditions and HP storms. This changes quickly around 20Z (second image), with much drier air intruding into the mid-levels. From there on, temperatures at around 700 mbs begin to warm up until by 23Z (third image) they've risen from 1.5 degrees C (18Z) to 5.9--a gain of nearly 4.5 degrees--and a slight cap has formed and becomes strong by the 00Z sounding (not shown). Note how the surface winds have veered, killing helicity as the cold front moves in. End of show for Lake Charles. Farther east in the Louisiana panhandle, you get much the same story at Baton Rouge, except the more potent dynamics appear later and more dramatically, with 1 km helicity getting downright crazy. I've shown two soundings here. The first, at 18Z, has a dry bulge at the mid-levels but moistens above 650 mbs, and by 20Z (not shown) it has become even moister than its Lake Charles counterpart, to the point of 100 percent saturation between 600 and 800 mbs. Helicities are serviceable but less impressive than to the west. There's a big change in the second sounding, this one for 00Z. The dewpoint line sweeps way out, and look at that wind profile! With a 60 kt low-level jet, helicities are no longer also-rans to the Lake Charles sounding; at over 500 m2/s2, they're hulkingly tornadic, and the sigtor is approaching 13. Mississippi is obviously also under fire, and I hope the folks in Alabama have taken the 2011 season to heart and purchased weather radios that can sound the alert at night. To those of you who chase today's setup--and I know there are a few of you who are down there--I wish you safe chasing. But my greater concern is for the residents of Dixie Alley who live in harm's way and aren't as weather-savvy, and some of who--despite the NWS's best efforts--may not be aware of what is heading their way this Christmas Day. Having just glanced at the radar, I see that the squall line is now fully in play. I'll leave you with a screen grab of the reflectivity taken at 1725Z. Have a blessed and safe Christmas. ADDENDUM: In watching the radar, it's obvious that the 12Z NAM was slow by an hour or so. Can't have perfection, I guess.

Winter System Hits the Midwest and Great Lakes

As I write, a 988 mb low is passing just south of me, and with it, a major winter storm is covering areas west of me with snow while in the Southeast, several states are under a 5 percent risk of tornadoes per the Storm Prediction Center. I'm not going to write a lot. I just want to tip my hat to this system as it moves through, because it is a humdinger. Here in Grand Rapids, we're presently getting a lot of wind and rain, and the rain will change to snow later tonight. Snowfall here looks to be minimal, an inch or less, but not a whole lot farther north, conditions promise to worsen quickly, with accumulations up to eight inches or more over the next 24 hours. The first map is a 12Z NAM snowfall map, courtesy of F5 Data; click on it to enlarge it. Below it, to demonstrate the contrasting weather conditions, is the SPC Day 1 tornado risk.

The Action Comes to Michigan

Curious about the SPC's Day 2 convective outlook for Michigan, I ran a few forecast soundings. Good grief! I can't remember when I've seen skew-Ts like these in Michigan. The one for Cadillac reminds me of June 5, 2010, in central Illinois, though I think the winds above 500 mbs were stronger in that event. It's late and I'm not about to write a lot. But I have a strong hunch that tomorrow early afternoon I'm going to be heading north on US 131. It's rough chasing in that part of Michigan, but anywhere in this state is challenging, and we don't see this kind of setup very often.

My First North Dakota Chase This Saturday

I've never chased storms in North Dakota, but that's about to change. Tomorrow Rob Forry and I are hitting the road for the severe weather event that's shaping up for Saturday along the Canadian border. This has been a puzzling scenario to forecast, with the models gradually aligning after painting some radically different scenarios. The NAM has wanted to move the system eastward faster and place the better  tornado action across the Canadian border, while the GFS and Euro have been more  optimistic and, I believe--I hope--more accurate. What the heck--Canada may get more shear, but North Dakota has the big CAPE. We'll find out Saturday. Lacking an extended driver's license that would grant me access to Canada, I'm counting on North Dakota to deliver. I feel confident enough that it will that I'm taking the chance. I keep eyeballing the region from Minot east toward Rugby and Devil's Lake, and north, and a bit south. Skew-Ts have looked consistently good in those parts, and there's plenty of CAPE to get the job done--around 4,500  J/kg MLCAPE per the GFS. My hope is that all that luscious, pent-up energy will produce something like what the NAM 4km nested CONUS radar shows at the top of this post. Come on! Big tubes and gorgeous storms drifting across the wide sublimity of the North Dakota landscape, and then steak and beer later on.

An Active Weather Pattern Moving In

These next few days look interesting severe-weatherwise from the northern Plains into the Great Lakes. Today holds the potential for a significant blow near the Missouri River in South Dakota, Minnesota, Nebraska, and Iowa. Here is a RAP forecast sounding for Sioux Falls, SD, for 00z tonight. I've been eyeballing that area via the NAM for a number of runs. Capping has been an issue for a while now, but NAM has consistently wanted to break the cap in the area I've mentioned. If I could have found a partner to split costs, I'd have left last night, but the thought of going it alone and blowing a wad of cash on a cap bust--a distinct possibility, with 700 mb temps hovering AOA 12 degrees C--spooked me. Now I think I should have taken the risk. Today could be another Bowdle day, and I wish I was in Sioux Falls right now. Some of the  indices there for this afternoon look pretty compelling, at least if the RAP is on the money. The cap could break between 22-23z, and if that happens, then walloping instability (mean-layer nearly 3,900 J/kg CAPE and -10 LI) and mid-70-degree F surface dewpoints will surge upward into explosive development, and ample helicity will do the rest. However, the SPC is not nearly so bullish as the above sounding, citing the complexity of the forecast due to capping and the lack of dynamic forcing. That's been a repeated theme. Today looks like one of those all-or-nothing scenarios where chasers will either broil in a wet sauna under merciless blue skies or have one heck of an evening. Boom or bust for those  who are out there. As for me, this evening I will either be watching the radar and beating my head against the wall or else congratulating myself on my good fortune for not going. But I'll also be packing my gear in preparation for tomorrow, and later tonight I'll be hitting the road with Bill and Tom. I'm uncertain what Sunday holds, but last I looked, the dryline by the Kansas-Nebraska border looked like a possibility on both the NAM and GFS. The weak link seems to be the dewpoint depression; it's wider than one could hope for, suggesting, as the SPC mentions in its Day 2 Outlook, higher LCLs. I haven't gone more in depth. We'll look at the model runs again tonight and pick a preliminary target for tomorrow.