Sunday, June 19, 2005

a successful chase

i got up on friday morning, intending to go to regina. i did that, but along the way wxdog steered me toward moose jaw, both because they have a great library there and because, according to him, the threat had shifted farther westward.

i got to the library and agreed with him. the question was, where exactly? there was great 0-6 km shear, there was lots of moisture and instability, but there wasn't yet a focus for the convective initiation. that's an important one. if you're looking for where they'll start, given a favourable environment, you need to find a focus, usually in the form of convergence--a dryline, a warm front, a cold front, a subtle wind shift, an outflow boundary--anything.

i meandered to swift current and stopped in their library (after taking about 20 minutes to find it, despite good directions) and i finally found the focus. just to the south of me, the wind shift line had sharpened up quite a lot. south of the boundary the winds were from the sse. north of the boundary they were almost due east. this was good. so i decided to take off south out of town based on that and also based on the fact that visible imagery showed a persistent cumulus field in the area, indicating enhanced lift. a tornado watch was issued for the area. (and btw, i came back here to find out an extreme rarity--the paspc had issued a high risk of severe thunderstorms for the area.)

as i left town i noticed storms starting to fire up straight ahead of me. i got south as quickly as i could, and i was greeted by a slowly strengthening thunderstorm with a ragged wall cloud underneath the southern flank--right in the right spot.

i called in my report of how it looked, and told them i would be watching it.

soon, the storm's wall cloud started to show marked rotation, a fact i relayed to the office. i told them that the rotation was tightening up, and that the right side of the wall cloud also had fairly violent upward motion on it.

15 minutes later this wall cloud dropped a funnel about halfway to the ground. again i called it in. (i think they may have been sick of hearing from me. ;) ) it's at this point (i think) that a tornado warning went out. soon enough, it dropped a brief tornado--it lasted maybe 5 seconds--and it went back into the cloud. the whole system was moving to the north, so i kept creeping in that direction. at the time i was near cadillac, sk. soon the wall cloud dissipated and started moving quite a bit north of my location, so i tried to reposition in that direction.

bad idea.

i got into some rain and small hail, and the wind was strong out of the north--indicating that i was in the outflow of the storm. a little farther north, though, the wind suddenly shifted to the east.

uh oh.

my spidey sense was tingling (okay, my conceptual model of a supercell was) and it told me that if this thing decided to drop a tornado, i could be in its path.

good move, dave.

as soon as i had turned around, my phone rang--it was a-pry. she said something along the lines of "good, you're alive". huh? soon enough, though, i saw why she was concerned.

as i got into the lighter precipitation, i saw something to my east. yes, it was a tornado on the ground. a pretty big one, an elephant trunk. had i kept going north then east, like i had been intending, i would have been directly in its path. this tornado ended up doing some damage in and near the town of neville--roofs damaged and the like.

this point here was a learning experience for me--a bird in the hand is worth two in the bush. or put otherwise, a tornado right in front of you is worth much more than repositioning for the possibility of a later one. too bad for me i had yet to learn this. i kept driving, trying to get into better position to see the next tornado this storm would produce. as it turned out, though, that would be the last one i would see that day. the road network out in southwest sk is not conducive to storm chasing, unless the storms are right near the path of a good roadway.

i drove around the area for the next while, trying to reposition myself and getting in between supercells, so i put down my tripod and caught another wall cloud and possible funnels (i haven't examined the tape yet) near shamrock.

then i went into the town of shamrock and learned another lesson. not the hard way this time, though. luckily. a wall cloud was sse of me and i wanted to get a look to see if it was putting down a tornado or more. all i had was a gravel road, though. a gravel road that had, in the previous half hour, received about 50 mm of rain. you can see where this is going.

the driving all of a sudden seemed mushy and slippery, kind of like driving on a sheet of ice covered in 2 inches of snow. i decided the best course of action would be to stop then and there. good move. i backed up out of there, very slowly, not even trying to turn around. the road was about 6 inches of mud where i was but had i gone farther it would have gotten much worse. as it was i was hubcap-deep in mud, and that was good enough for me. luckily i made it out of there without further incident.

i finally got into moose jaw around 11 pm local time. since the cell phone coverage wasn't very good, i hadn't been able to phone ahead to book a room for myself. (note to self; book ahead!) i think i got the last room in town. 69 dollars. actually, it wasn't bad for late friday night in early-mid season.

like mom always made me do when i was bad, i went to bed that night without any dinner. and that's really too bad, because i should have had the traditional storm chasing tornado celebratory meal: steak. for the vegetarians out there, i don't know what to say. perhaps you could suggest an alternative? and btw, it's bad form to have steak while you're on a chase and you haven't seen a tornado--it's considered a jinx. ribs, fine. burgers, fine. pretty much anything else, fine. but have steak on an unsuccessful chase, and you're likely in for some ribbing. pun definitely intended.

saturday looked pretty good, too, over southwest manitoba. since that was in the direction of home, i decided to go chase around there.

i got to virden around 1 pm and things were still well capped, so i stopped in for a library break. again, great library. it would be nice to have data on the road rather than only at select stops. but i digress.

i left the library and decided to play the southern end of the cumulus field. convergence and upper cooling were to be coming in, so it looked like the sweet spot.

wxdog called me and told me some americans--including tim samaras--were planning on chasing the area today. about 4 seconds after he said that, i was passed by a couple of vehicles with colorado plates, and one of the plates said "strmchsr". hmm, i wonder who that could be. ;)

when they stopped on a side road, i stopped, got out and introduced myself. we chatted for about a half hour and then i decided to drift to the northeast and meet up with paul and the gang from college of dupage, who were in brandon.

we drove around for a long time, wondering if things would go at all. finally, near pipestone, storms started going along the convergence line. good deal. we went off in that direction and got deflated. the storms were briefly pulsing up and then dying. what the? there was plenty of instability and shear. why were they not going huge?

at about 7 o'clock we took off to the east for a gas and bathroom and disappointment break in souris. after coming back out of the store, we noticed much stronger towers to the west. paul has an internet connection in his van, so we could see it on the minot radar. it was starting to have a kidney bean shape, typical of a supercell, so we decided to go back west and check it out.

when we got there it was already impressive. definite supercell with good mid-level rotation on it, and a somewhat ragged wall cloud. i called the paspc and told them what i saw. soon after, based on what i was seeing (at least a little bit) but mostly based on doppler radar, they issued a tornado warning for it. paul and the gang headed north and i followed them. no, dave, next time listen to yourself. i thought that this storm would be crossing the highway before the next road and would get us stuck, and i was right. i got quarter-sized hail in the storm and decided to turn around--and go back south slowly. i didn't want to be driving blind into a tornado.

well, it never did end up putting down a tornado. i think it's probably because, with everything else in place, the winds at the surface were just too wimpy. in the storm environment they were light out of the se. i wanted 20 knots from straight east. then i'd probably be telling a different story here.

but still, it was a beautiful storm. i got lots of pictures of it, mostly of the wall cloud but also of the mid-level mesocyclone and the towers going up. i hope they turned out well.

as i was heading home east of brandon, i looked in my rear-view mirror and saw that the storm had reintensified, so i stopped and took some pictures. the wall cloud it was making at that point only lasted for about 10 minutes and then dissipated.

i put 2100 km on my car in 2 days. extremely tiring. i don't know how i'm going to manage driving like that for 5 days straight.

maybe i should just hope the storms aren't very far away. ;)


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