After last Saturday’s busted waterspout chase, I’ve become curious about what goes into predicting waterspouts. It’s an area I haven’t paid much attention to, but after reading a paper on waterspouts sent to me by Mike Kovalchick, I’m interested in learning their forecasting parameters.
I had always thought there were just two categories of waterspout: non-mesocyclone and mesocyclone. But the paper presents four categories: tornadic, upper low, land breeze, and winter. All of them fall within a range of variables depicted on a “waterspout nomogram” that correlates convective cloud depth and the difference between water temperature and 850 mb temperature.
Tornadic waterspouts cover a broad swath of the nomogram. The remaining three kinds fall within more specific territory:
* Land breeze waterspouts require a minimum convective cloud depth of 5,000 feet, stretching all the way up to 32,500 feet, and water/H85 temp differences between 11 and 19 degrees C.
* Upper low waterspouts require a minimum convective cloud depth of 6,500 feet, stretching up to 36,500 feet, and water/H85 temp differences between 9 and 19 degrees C.
* Winter waterspouts, as one would expect, are a different animal. Convective cloud depths range from 2,250 feet to 9,750 feet, with water/H85 temp differences starting at 24 C and apparently extending beyond that indefinitely.
* All of the above presume 850 mb wind speeds of less than 40 knots.
This is obviously an extremely simplified summary which I’ve extrapolated from the waterspout nomogram. The nomogram brings out variables that I haven’t addressed here, and it’s well worth checking out in the aforementioned paper (see above for link).
Developed by Wade Szilagyi of the Meteorological Service of Canada, the nomogram is in use for predicting Great Lakes waterspouts, and evidently is under consideration for use in the Mediterranean Sea as well. It looks to be an easy-to-understand tool, and one I’ll surely be using as the Lake Michigan waterspout season ramps up.
Yes, I was also curious about waterspout formation, and found the same little article you did. I had researched a few weeks before last saturday, and found that article,and nomogram. I then proceeded to grab some bufkit profiles near the shore of Lake Michigan, and begin my forecasting process. At first I was a little worried about the cloud depth, as it didnt look great, but as the days got closer, it got better-but not as great as it could be. Luckily BUFKIT has a lake effect setting to set water temps (which I grabbed off the NOAA GL Forecast) and then it gives you your surface temp to H85 temp split, or delta-t. Two days before last saturday, I became more worried about the the winds, as they showed 20-30kts. All forecasting aside, I headed up to Muskegon to look for waterspouts, but busted. Im gonna assume the winds were to strong, as I recorded 21mph sustained winds and 32.6mph gust-all over 4 hours. Oh well, I guess there is next time.
Hello gentlemen.
I helped write that article! I have been researching waterspouts over the Great Lakes for the past 15 years and have developed the Waterspout Nomogram. Feel free to use it. Also, if you see a waterspout in the future then send me a note or picture at wade.szilagyi@ec.gc.ca.
Wade
I’ve been remiss in responding, but I guess it’s time that I did.
L.B., where you were in Muskegon looked like the better target as the cloud tops were higher, but we didn’t have time to head up there. I guess it didn’t matter, since no one got any spouts that day no matter what locale they targeted. The winds were pretty strong, and my guess is that they undercut any vertical stretching of vorticity.
BTW, I’m looking forward to bumping into you on a local chase sometime. Not sure that’s gonna happen this year, though–convective weather seems to have gone into retirement in Michigan.
Wade, what a pleasure to hear from you! Your waterspout nomogram is quite a neat device, and the article was great. Both have been the most helpful thing I’ve come across so far when it comes to forecasting waterspouts. Since I’ve got your contact info, I’ll definitely shoot you photos and notes when I finally have the good fortune to observe a spout.