Forecast Model Simulations for 1965 Palm Sunday Tornadoes: Part 2

The drive down to the WFO at State College, Pennsylvania, was well worth my while (see my previous post). Operational forecaster and research meteorologist David Beachler was a pleasure to work with--personable, patient, and eager to help me understand the exhaustive forecast simulations he had produced on the 1965 Palm Sunday Tornadoes. Having pored over the data with David, gaining his insights on its strengths and weaknesses, I am now extremely excited about what I've got on my hands. David's modeling uses the WRF-ARW 40 km. The resolution is too coarse to offer the fine details that the SPC is capable of producing, but it gives an excellent overall feel of what forecasters and storm chasers might see in the models if the Palm Sunday synoptic setup were to unfold today instead of forty-five years ago in 1965.

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There's no way I can begin to cover all the material, which in any case I need to sift through in order to put together a reasonably concise and meaningful scenario. But I can at least give you a sample of some of the stuff I've got to work with. Click on the following images to enlarge them. First, here is a hand analysis of the kind that is accessible to anyone through NOAA's historical daily weather maps archives. Besides the surface map for April 11, 1965, you also get the previous day's surface map, 500 mb chart, and other info. It's what you would have encountered when you turned to the weather page in the newspaper that morning. What you would never have seen--because parameters such as CAPE, CIN, helicity, and so on didn't exist back then, and because even if they had existed, the forecast models which could have depicted them were still years down the road--is this map showing SBCAPE and low-level shear. The map is for 2200Z, or 6 p.m. EST--roughly the time at which tornadoes began moving through northern Indiana. It gets even better. Here is a model sounding for KGRR, also at 2200Z, using WRF-ARW Bufkit data. The skew-T and hodograph depict the conditions that were shaping up to produce the F4 Alpine Avenue tornado that formed around 6:50 p.m., as well as other tornadoes in west and southwest Michigan that day. The helicity is impressive--and look at those winds! Forty knots at 850 millibars is no mere puff of air. What really excites me is that, using RAOB's cross-section feature, I should be able to reconstruct a vertical profile of the atmosphere for the entire outbreak area. I'm not sure how deeply I want to go with that, but I have the capacity. Bear in mind that I'm just showing a couple of representative glimpses derived from a 00Z, day-one model initiation. In fact, David provided me with a range of initiation times that allows me to get a good sense of how the maps might have progressed from several days prior to the actual tornado outbreak. In practical terms, the maps and model sounding data I've got correlate to the NAM. They're not the NAM, but for storm chasers who typically work with the GFS, ECMWF, GEM, NAM, and RUC, what you see here is probably closest to what you'd find using the North American Mesoscale Model. That's all for now. This has been a time-consuming post, and at 2:30 in the afternoon, I need to pull away from it so I can bathe and eat. I didn't arrive home until 3:00 a.m., so it's time for this road warrior to reset his time clock and get on with the rest of life.

August 20 Tornadoes in Canada

Yesterday's storms marched across West Michigan pretty uneventfully, but as they moved east, they grew fangs. Moving into better helicity and shear, they began to develop supercellular characteristics from around Saginaw down into Ohio. It was interesting to track them on the radar, but I had no idea what was coming as they moved into Canada. KDTX showed some small but nicely shaped and very suspect-looking cells moving out over Lake Huron. Evidently a few of them meant business. Tornadoes began dropping in Ontario, with the area around Toronto getting slammed, and with one fatality recorded in the town of Durham. Here's a video of the strong tornado that hit Vaughan, just north of Toronto. Looks like the person who posted on YouTube lifted the footage off of the news. I looked for other footage, but while there's plenty out there, much of it isn't of very good quality. This is some of the best I could find. There is presently one pretty dramatic, close-range clip of the Durham tornado which a young woman shot with the video cam on her cell phone, but I'm not confident that the link will last very long. Maybe this one won't either, but I'm crossing my fingers and hoping it does.

Cool-Weather Wall Clouds

So there I was, driving down I-96 toward my mother and sister's house in Grand Rapids this afternoon, when I saw what at first glance looked like a wall cloud. It looked like one at second glance, too, and third, hanging off of a cumulus tower in the distance. Severe weather wasn't in the outlook today, and in fact, the afternoon was coolish and not particularly moist, with spotty showers but no thunder or lightning. I was unaware of any reason to be on the lookout for abnormal weather, though the extent of the vertical development in the cumulus clouds coupled with their nicely sheared look would have been a tip-off under more propitious circumstances. Anyway, I was intrigued by the cloud formation, but not quite prepared to call it anything more than a lowering at that point. It was falling apart over Grand Rapids by the time I turned north onto the East Beltline. But the show was far from over. Another large towering cumulus several miles to my northwest was exhibiting an even larger, blocky lowering which wasn't showing any signs of dissipating. That did it. It was time to get close enough to this thing to see just exactly what it was. This was a simple matter. The cloud was drifting quite slowly, and intercepting it involved nothing more elaborate than continuing north up the Beltline past 7 Mile Road, then pulling into a small turn-in, where I had an unobstructed view from maybe half a mile away. The cloud was indeed a wall cloud. I could see a weak updraft dragging scud up into it, and even a hint of an RFD. More important, the cloud was circulating--very slowly, to be sure, but unmistakably. As it moved closer, I even observed a small, anticyclonic vortex spinning almost directly overhead. There was obviously enough shear and helicity in the atmosphere to create some interest, and I had a nice front-row seat. Just wish I'd had my camera with me, but as I said, I wasn't expecting anything weatherwise today that would have made me think to grab it. What I was seeing struck me as more fascinating than threatening, but I decided to call KGRR and report it anyway, just for the record. The met who took my information said he wasn't surprised. He told me that the office had already received several reports of waterspouts out on Lake Michigan, plus other reports of funnel clouds. Sounded like a cold air funnel outbreak. My buddy Kurt Hulst called later to tell me that he, too, had seen a wall cloud over Caledonia from where he lives in Kentwood. If I'd been home, it would have been a front door delivery, but of course I wasn't. Seems to me, though, that Kurt said he got some photos. I hope so, because I'd like to see what I missed. Days like today just go to show that the weather does what it wants, when it wants. Maybe the local WFO will offer an analysis of today's conditions. That would be cool. Lesson learned: take my camera with me wherever I go.

Chasing Storms after the Concert

Bill, Kurt, and Tom are leaving tonight to chase Saturday's setup out west. I'm staying behind to play with Francesca and Friends at the 2009 Grand Rapids Festival of the Arts. Ordinarily I'd feel a bit torn, but I have an idea that the better action will be on Sunday and--from the looks of the 12Z NAM-WRF--Monday. So when I step onto the stage tomorrow afternoon, unless between now and then a confluence between the NAM and GFS suggests that capping will suddenly no longer be an issue and Armageddon is going to break out in the Great Plains, I will be a man at peace. But directly after the concert, I plan to pack my bags and head for the Corn Belt, where I'll hook up with the guys and chase storms on Sunday and, if the present NAM-WRF comes at all close to verifying, Monday. Frankly, I'm somewhat skeptical about Monday. Previous runs have consistently painted such a different scenario, with majorly veered surface winds and a unidirectional flow overall, that the 12Z's placement of the weak surface low in eastern Iowa seems too good to be true.  Here's an image from F5 Data showing sigtors, APRWX sigtor, surface wind barbs, and H5 wind speeds:

12Z NAM-WRF for 0Z Monday

12Z NAM-WRF for 0Z Monday (F5 Data)

Suddenly all the elements in terms of moisture, instability, and shear are lining up, along with a 7 sigtor in Iowa and even a 4 in southwest Michigan (in the usual lakeshore location, Berrien County). Makes me more than a little suspicious. But I think I can at least count on Sunday, and we'll see whether future model runs continue to paint a rosier trend for Monday in Iowa and the Great Lakes. So it's play my saxophone on Saturday, then chase storms on Sunday and maybe Monday.  That's about as nice an arrangement as I could possibly ask for--other than for this year to finally be the one where our act at the Festival doesn't get interrupted by a hailstorm. That has happened three years in row. But I've got a good feeling that tomorrow is the day when we'll finally make it through intact. That'll be good. I'd just as soon save the hail for the day after.