Radar loop of storm interactions on the Raton Mesa, 6/24/18

Discussion in 'Advanced weather & chasing' started by John Farley, Jun 27, 2018.

  1. John Farley

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    I was intrigued by some of what I saw on my chase on 6.24 (see Reports thread that day for details and a few pictures, more to come), including especially the funnel look-alike and the seeming handoff to a new storm that happened around the same time. I did notice a little of this on radar during the chase, and thought there may have been a storm split while I was between Branson and Folsom. But the meso that produced the interesting striation features did not seem to be anti-cyclonic, and in a true storm split it likely would have been. So I decided to download some radar images and make a loop, and that was very revealing: Here is the loop:



    Several interesting things going on in this loop, which runs from 2154Z (3:54 MDT) to 0033Z (6:33 MDT). In the first five frames, you can see the LP supercell tracking east just north of the CO/NM line, through the Trinchera and Branson areas. The annotation on the fourth frame notes the formation of the new supercell farther west near Trinidad, although you can see the very beginning of its development a couple frames earlier. By the 7th frame (2237Z or 4:37 p.m. MDT), the new supercell, now east or SE of Trinidad, is becoming quite strong, and the first of a series of special weather statements and eventually SVR warnings is issued. Also around this time a new cell forms just west of the main one, but it does not do much for a while. Over the next four frames or so, the main storm rapidly intensifies and takes a turn to the southeast into New Mexico. This corresponds to the time in which the wall cloud appeared southeast of Trinidad. By 2318Z (5:18 MDT), the new storm just to the west of the main one is intensifying and the movement of the main storm turns back to the east again. It is just a few minutes after this, 5:24 p.m. according to my camera's time stamp, which is very close, that I observed the striation features, the first of them being the feature that I initially thought was a funnel cloud. Thus, this definitely happened at a time when the two nearby cells - the one that up to then was the main supercell and the new cell just to its west - were interacting with one another. In the next radar frame, just one minute after I observed the aforementioned features, the up-to-then main cell is starting to turn a bit to the northeast and the new cell that formed to its west is surging southeast into NM, much like the other one had done earlier. (This is the frame with the annotation, "Wrapping feature occurred at this time.") By the next frame at 5:32 p.m., the new cell to the west has become dominant as it continues its southeastward surge further into NM, with dramatic strengthening, while the formerly-main cell is crossing back east into Colorado. This is when I saw the "stacked plate" meso - the same one associated with the funnel look-alike - looking northwest from the intersection of routes 551 and 456.

    Another thing I would note - I put pictures of the funnel look-alike on my Facebook page (again, you can see them in the Reports thread, so won't re-post here), and there was interesting discussion in which, among other things, @Skip Talbot asked if the storm was weakening at the time. I said it was not, which overall was true, but now looking at the radar loop, the cell associated with the features was just starting to weaken as the handoff occurred to the cell to the west/SW. So perhaps this kind of feature is in some way linked to a weakening mesocyclone.

    Beyond that, the radar imagery during this time period confirms several things to me. First, this was NOT a cell split - the two cells were separate from the time the second one formed. Thus, I was right in thinking that the meso of the original one was cyclonic the whole time. Second, there seemed to be something of a handoff of the main energy from the original cell on the east to the new one on the west. Third, and a bit more speculatively, there may have been a Fujiwhara effect going on between the two cells, as they for a short time started to rotate around one another, with the western cell turning to the southeast and the eastern one to the northeast. Alternatively, it may have just been a case of the eastern one becoming more influenced by the upper winds as it weakened. Either way, once this change in the movement of the two cells had happened, the western one, like the right split in a true cell split usually does, became the dominant storm, and surged southeast toward Des Moines producing severe hail. Yet another cell formed to the west of the new one and also intensified, but it never became dominant. Clearly there were some very interesting storm interactions going on here! One other thing I think was very likely is that some of this ws influenced by terrain. When the handoff and possible Fujiwhara effect occurred, the storms were crossing the Raton Mesa, an area of high terrain that extends eastward into the plains from between Raton, NM and Trinidad, CO. It often plays a role in helping to trigger strong storms in this area, but in this case I think it also probably affected some of the specifics of the storm interactions that occurred. I was literally in a canyon near the center of the mesa when I observed the funnel look-alike/striation features. Yet another interesting element in a very interesting chase day.
     
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  2. John Farley

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