Dave Kaplow
EF4
Mods: I thought it best to keep this a separate thread from the other May 24 discussion dealing with events elsewhere in the US. If this was wrong to do, please move this to the appropriate place. Thanks.
I’m kind of surprised at the way the severe weather threat yesterday in the Northeast was handled, both prior to and as the event unfolded. There were several interesting actions either taken or not taken by both SPC and local NWS offices, and I‘d love to know why certain decisions were made the way they were.
The models indicated that there were going to be widespread strong thunderstorms in the area, and the night before the event I thought a Slight Risk was likely and said as much here on ST. SPC eventually did upgrade to Slight, but I’m baffled by the decision to go with a 0% tornado risk. After looking at the NAM, the parameters all seemed to indicate that supercells were a definite possibility, and I was intrigued to see that most of the available shear/helicity was progged to be in the lowest kilometer. I know things like tornado probabilities are extremely hard to forecast with any accuracy, and I suppose the process is always going to be a bit subjective, but to say flatly that there is zero likelihood of any tornadoes forming in an environment where surface based supercells appear likely, that’s a pretty bold statement. The zero seems to have held up so far, though, since there were in fact no tornado reports, so I guess I should really be impressed by SPC’s accuracy. I dunno, I guess that’s one way of looking at it.
What really perplexes me is the lack of even a severe watch box. There was a “watch possible†MD, and then after things were well underway with several ongoing supercells, including one T-warned, there was a follow-up “watch unlikely†MD, and that was that. No watch was ever issued. I think 4 cells were eventually T-warned at one time or another (but maybe some shouldn’t have been, which I’ll get to) and there were numerous severe warnings throughout the afternoon, so in the end it turned out to be quite an active day, as the Storm Reports page shows. Clearly the Slight Risk verified, and maybe even a small Mod Risk would have verified, but just as clearly a Watch would have been very helpful to local officials and the public. I really don’t know why one wasn’t issued.
Now lets look at the tornado warnings. The first significant supercell in CT developed near Hartford, with backbuilding helping to boost helicity as it often does around here. This cell was really spinning like a top, on velocity scan it reminded me of the cell last year that dropped a big multivortex tornadic waterspout off Milford. I figured a T-warning was imminent. Then another supercell developed in NW CT that was also obviously rotating, and for a while both these cells were showing nice hooks on radar. To my knowledge the Hartford cell was never T-warned, and the Danbury cell was warned only after it had obviously lost most of it punch and rotation. There were a couple of further tornado warnings issued a bit later for remnant cells that looked laughable on radar. I suppose it’s possible that a TVS may have popped up on these cells for a scan or two, although if so I missed it, but I simply can’t believe there was any kind of persistent tornadic signature, especially on the last warning for New Haven at 6:10 for a cell I could barely even locate on radar, let alone see to be rotating. I assumed at the time that there must have been some kind of visual reports triggering these warnings, yet the text on all the warnings stated only that they were doppler indicated, with no mention of any sightings or reports.
So, on the one hand we have SPC seeming to want to downplay the whole event, with no watch box and 0% tornado probs, and on the other hand there were local NWS offices issuing radar-indicated tornado warnings for cells that were pretty clearly in no danger of tornadoing, but only after seemingly ignoring those same cells when they were at their most dangerous. At least that’s how things looked to me. Just to be clear, I emphatically do not want to criticize either SPC or NWS Upton in any way. They both do a superb job. It would be nice to know, though, just what their thinking was for this event, so I could figure out what it was they were seeing that I wasn’t, or vice versa.
I’m kind of surprised at the way the severe weather threat yesterday in the Northeast was handled, both prior to and as the event unfolded. There were several interesting actions either taken or not taken by both SPC and local NWS offices, and I‘d love to know why certain decisions were made the way they were.
The models indicated that there were going to be widespread strong thunderstorms in the area, and the night before the event I thought a Slight Risk was likely and said as much here on ST. SPC eventually did upgrade to Slight, but I’m baffled by the decision to go with a 0% tornado risk. After looking at the NAM, the parameters all seemed to indicate that supercells were a definite possibility, and I was intrigued to see that most of the available shear/helicity was progged to be in the lowest kilometer. I know things like tornado probabilities are extremely hard to forecast with any accuracy, and I suppose the process is always going to be a bit subjective, but to say flatly that there is zero likelihood of any tornadoes forming in an environment where surface based supercells appear likely, that’s a pretty bold statement. The zero seems to have held up so far, though, since there were in fact no tornado reports, so I guess I should really be impressed by SPC’s accuracy. I dunno, I guess that’s one way of looking at it.
What really perplexes me is the lack of even a severe watch box. There was a “watch possible†MD, and then after things were well underway with several ongoing supercells, including one T-warned, there was a follow-up “watch unlikely†MD, and that was that. No watch was ever issued. I think 4 cells were eventually T-warned at one time or another (but maybe some shouldn’t have been, which I’ll get to) and there were numerous severe warnings throughout the afternoon, so in the end it turned out to be quite an active day, as the Storm Reports page shows. Clearly the Slight Risk verified, and maybe even a small Mod Risk would have verified, but just as clearly a Watch would have been very helpful to local officials and the public. I really don’t know why one wasn’t issued.
Now lets look at the tornado warnings. The first significant supercell in CT developed near Hartford, with backbuilding helping to boost helicity as it often does around here. This cell was really spinning like a top, on velocity scan it reminded me of the cell last year that dropped a big multivortex tornadic waterspout off Milford. I figured a T-warning was imminent. Then another supercell developed in NW CT that was also obviously rotating, and for a while both these cells were showing nice hooks on radar. To my knowledge the Hartford cell was never T-warned, and the Danbury cell was warned only after it had obviously lost most of it punch and rotation. There were a couple of further tornado warnings issued a bit later for remnant cells that looked laughable on radar. I suppose it’s possible that a TVS may have popped up on these cells for a scan or two, although if so I missed it, but I simply can’t believe there was any kind of persistent tornadic signature, especially on the last warning for New Haven at 6:10 for a cell I could barely even locate on radar, let alone see to be rotating. I assumed at the time that there must have been some kind of visual reports triggering these warnings, yet the text on all the warnings stated only that they were doppler indicated, with no mention of any sightings or reports.
So, on the one hand we have SPC seeming to want to downplay the whole event, with no watch box and 0% tornado probs, and on the other hand there were local NWS offices issuing radar-indicated tornado warnings for cells that were pretty clearly in no danger of tornadoing, but only after seemingly ignoring those same cells when they were at their most dangerous. At least that’s how things looked to me. Just to be clear, I emphatically do not want to criticize either SPC or NWS Upton in any way. They both do a superb job. It would be nice to know, though, just what their thinking was for this event, so I could figure out what it was they were seeing that I wasn’t, or vice versa.
