At the beginning of the briefing we discussed yesterday real-time IOP event over the Sterling, VA WFO CWA. We had the ability to use the PGLM output from the DCLMA for this event. Most of the warnings issued were for severe wind threats and were fairly marginal. One of the forecasters mentioned that he focused on the PGLM products because of the marginal nature of the event to try and pick out regions of greater importance since the radar and MRMS products were showing similar features for most of the convection around the area. However, due to the marginal nature of the event, no strong conclusions were drawn as to the usefulness of a lot of the experimental data. One of the forecasters brought up the idea of creating regional versions of some of the products to try and draw more information from them. This may eventually be useful for products like the CI and cloud-top cooling products since we have seen some regional dependence on the product performance (ie - diagnostic over SE US)
We also discussed the performance of the UWCI over the same area. The forecasters reiterated the lack of detection over WV/VA border from yesterday's blog post. We believe that this was due to some microphysical issues being presented in the cloud typing product that were masking out the CI signals. We mentioned that we had wished we had moved to SD sooner, which is where we ended up for the remainder of yesterday's IOP. There were a lot of signals over that area (see image above), but we were unsure as to the timing of them since we were not watching in real time. This would be a good case to look at in the future. Also, notice the lack of signals over the Sterling and State College WFO areas where we focused at the beginning of the day. Jordan Gerth discussed with the forecasters about the idea of providing a cloud-top cooling rate 'image' with no filtering, which would allow for the forecasters to see all areas of cooling/warming regardless of cloud motion or other effects that are currently removed. This would allow the forecasters decide for themselves what are false signals and may be particularly useful for determining the life cycle of MCS's and weakening supercell storms.
24-hour overshooting top (left) and thermal couplet (right) detections for 16 June 2010.
We examined the overshooting top and thermal couplet detections (see images above) and saw that both the overshooting top and thermal couplet detections did correlate well to the location of the severe weather in this case, especially over SD. However, when these were seen during the real-time IOP, it was already obvious that severe weather was occurring based on reports being received and the standard radar data. The overshooting top detections that continue further east, as well as the blob of CI nowcasts east of the tornadic storm were questioned by the forecasters since they occurred after the IOP ended and they were not sure how legitimate they were. We did look back very quickly to see what happened and it seemed as though a MCS developed later on associated with many additional warnings and it would have been nice to see the performance of the products in that instance. Again, this would be a good case to look at in the future. We will attempt to archive the data, but it may be difficult since we do not yet have dedicated disk space to do so.
The plan for today is to operate over MN and IA. This is our last chance for real-time IOPs and it looks like it should be a good one for GOES-R with the lack of cirrus in the area... assuming we get started soon enough.
Chris:
ReplyDeleteIt is important to stress that:
1) All severe weather events are not necessarily reported.
2) Overshooting tops can be present in a "non-severe" storm. The product was developed with aviation as the primary target audience, but the results from this year's HWT have shown a reasonably good correlation with severe weather.
3) An OT detection without a severe weather report should not be considered a "false alarm"...it is only a false alarm if the detected pixels are obviously not an OT.
Please note that at no time did I mention that the OTs that occurred during this event were false alarms. Since we are evaluating these products in severe warning operations we want to compare what we see to severe reports. Also, the forecasters were curious to see the CI and OT detections further east not directly due to the lack of severe reports but rather because they didn't think any additional convection developed after they were done in the IOP.
ReplyDeleteI guess I misread the post above where it says: "and they were not sure how legitimate they were". Over the past few weeks, there have been a couple other insinuations that a lack of direct OT-severe weather matchup implies an OT false alarm. I suppose within the EWP framework, it may be considered a "false detection", but daytime comparisons would suggest that the product is doing quite well in recognizing clouds above the tropopause.
ReplyDelete