During today's EWP forecaster daily briefing, we discussed the previous day's activities over DC and then over eastern CO later on in the evening around 2345 UTC. When asked about how the CI products performed during the early event, the forecasters offered the following comments...
"It was complex and challenging to use in this sort of widespread event. We primarily used the UAH CI product yesterday. It was generally pretty noisy in this kind of pattern, but I did see some clusters and bands with some mixed success. In some cases it popped up where there was clearly some convection ongoing, but there where definitely cases where it did show some good signals. I would like to see it more in some cases like this that are difficult."
"I was watching it today over the same area and it gave 45 minutes to 1 hour lead time over lightning."
For today we have decided to operate over western OK to capture some clean slate CI as well as give us a chance to examine some of the other experimental products, such as the PGLM, which are limited to specific domains... one of which being over Oklahoma.
Wednesday, May 18, 2011
Tuesday, May 17, 2011
SATCAST CI Nowcasting: Translation & Evolution
One substantial improvement to increase the utility of the SATCAST CI algorithm (the GOES-R Proxy CI Algorithm) will be including details on where a given object, forecasted to become a new convective storm, is moving. For a forecaster, a present limitation of this CI nowcast product is that there remains uncertainty on where a nowcasted cumulus cloud object will in fact be located when it produces ~35 dBZ intensity rainfall (or perhaps lightning, if the environment is conducive). The example shown illustrates how adding propagation information will help in the CI nowcasting process, especially since the cloud object evolves substantially as CI occurs and thunderstorm development proceeds.
Shown is an example between 1432 and 1645 UTC 17 May 2011. The synoptic setting was a well-defined upper low, with strong cyclonic rotation and cold air aloft, leading to scattered generally low-topped, shallow convective storms. RUC surface-based CAPE values were 500-700 Jkg^-1. Convective clouds were propagating northwestward from central North Carolina to south-central Virginia. Circled is a northwest-southeast oriented cumulus cloud line in the vicinity of Raleigh, NC at 1432 UTC (Fig. A), with an added propagation vector included. Figures B (1445 UTC) and C (1602 UTC) show where the developing cumulus clouds and new storms, respectively, had moved since 1432 UTC. CI occurred by 1515 UTC; the 1606 UTC radar image is also shown. The cumulonimbus cloud with an obvious anvil is seen extending into far south-central Virginia at 1645 UTC (circled in Fig. D). In Fig. D, the full translation vector is shown beginning where the first object in Fig. A was seen. Only a few lightning flashes were observed by 1645 UTC associated with this storm. In this example, the translation vector points in an unusual direction, with storm propagation toward the northwest. This translation vector will also help forecasters maintain identification of a developing cumulus cloud, which will change substantially (in terms of size and shape) as it evolves, leading to less uncertainty in a CI nowcast.
Future enhancements to SATCAST will include translation vectors per nowcasted objects designed to help forecasters more precisely predict the location where heavy (~35 or greater dBZ) rainfall will occur. In many cases, the distance (time) between a highlighted CI object can be several 10's of kilometers (30-60 min) from where the rainfall/thunderstorm is actually observed to occur.
CI over VA
Posted by EWP forecaster and taken from EWP blog...
"Widespread cumulus fields forming across central eastern VA and UAHCI products capturing this much better than CIMSS in this case, which is a very moist, weakly unstable, but uncapped environment (almost tropical). While most new CI IDs are very scattered to isold in nature, now beginning to see some banding or clustering, which actually matches very well with at least one 4km WRF (12Z run for SPC…see second image above), and will be watching to see if the IDing of this banding of CI zones within otherwise wideapread cu field helps to identify where stronger storms could soon be forming in this kind of environment."
Steve Keighton
"Widespread cumulus fields forming across central eastern VA and UAHCI products capturing this much better than CIMSS in this case, which is a very moist, weakly unstable, but uncapped environment (almost tropical). While most new CI IDs are very scattered to isold in nature, now beginning to see some banding or clustering, which actually matches very well with at least one 4km WRF (12Z run for SPC…see second image above), and will be watching to see if the IDing of this banding of CI zones within otherwise wideapread cu field helps to identify where stronger storms could soon be forming in this kind of environment."
Steve Keighton
17 May 2011 AFD
The following post was made by EWP forecasters for their morning area forecast discussion (AFD) and taken from the EWP blog...
"Convection ongoing across Carolinas into Virginia this morning, and convection is expected to continue and intensify this afternoon given some clearing in warm sector and minimal cap. Nearly saturated environment, low-cape/moderate shear environment will result in strong and possibly severe storms. Although damaging wind gusts will be primary concern, low-lcl environment will keep threat of brief/weak tornadoes with initial development of convection primarily over eastern Virginia into eastern North Carolina where low-level cape/stretching potential will exist. Warm front extending sw-ne across northern portions of Virginia will need to be monitored as well with conentrated low-level shear. CI satellite detection possible early in the event before cirrus canopy becomes an issue. Hi-res models forecast banded convection near cold core and initiation of bands with CI detection may prove useful where higher impact areas will evolve. Already some more obvious clusters of CI detection using UAH product are highlighting areas in srn VA/nrn NC where new 12Z SPC 4km WRF is fcstg clusters of convection near short wave to develop early afternoon. CI products may continue to be useful to help identify where these potential severe clusters/bands may develop within the wider scattered shallower convection expected to develop. Value of 3dvar may prove useful as well where low-level vort and updraft fields can help warning forecasters concentrate on regions where low-level cape/shear are maximized. Good opportunity to experiment with utility of many 3DVAR products with shallower convection. Same with MRMS products. In addition, some of the nearcast differential theta-e/PW products indicating severe potential through mid to late afternoon over central VA shifting NW into northwestern VA…consistent with local WRFs and SPC WRF ideas.
High plains convection will be possible near developing dryline across eastern Colorado/western Kansas. CI detection will be useful late this afternoon and early this evening as it may take a while for CI once cu develops. Although shear will be increasing through the day, moisture availability will be a concern for more than LP type supercells, especially as storm move off of higher terrain.
Warning ops – our feeling is that initial warning ops, perhaps through at least 21z, should be centered on mid-atlantic region with the option of shifting west to Colorado eastern plains and western Kansas after 21z for possible initiation of isolated/scattered supercells. Greatest value of satellite CI detection and 3dvar fields may be most useful over eastern ops area, although CI detection along with OUN WRF output could be utilized out west. Expecting mainly a hail threat with the LP-type storms in the Plains, and evaluation of some of the MRMS products would be helpful as well."
"Convection ongoing across Carolinas into Virginia this morning, and convection is expected to continue and intensify this afternoon given some clearing in warm sector and minimal cap. Nearly saturated environment, low-cape/moderate shear environment will result in strong and possibly severe storms. Although damaging wind gusts will be primary concern, low-lcl environment will keep threat of brief/weak tornadoes with initial development of convection primarily over eastern Virginia into eastern North Carolina where low-level cape/stretching potential will exist. Warm front extending sw-ne across northern portions of Virginia will need to be monitored as well with conentrated low-level shear. CI satellite detection possible early in the event before cirrus canopy becomes an issue. Hi-res models forecast banded convection near cold core and initiation of bands with CI detection may prove useful where higher impact areas will evolve. Already some more obvious clusters of CI detection using UAH product are highlighting areas in srn VA/nrn NC where new 12Z SPC 4km WRF is fcstg clusters of convection near short wave to develop early afternoon. CI products may continue to be useful to help identify where these potential severe clusters/bands may develop within the wider scattered shallower convection expected to develop. Value of 3dvar may prove useful as well where low-level vort and updraft fields can help warning forecasters concentrate on regions where low-level cape/shear are maximized. Good opportunity to experiment with utility of many 3DVAR products with shallower convection. Same with MRMS products. In addition, some of the nearcast differential theta-e/PW products indicating severe potential through mid to late afternoon over central VA shifting NW into northwestern VA…consistent with local WRFs and SPC WRF ideas.
High plains convection will be possible near developing dryline across eastern Colorado/western Kansas. CI detection will be useful late this afternoon and early this evening as it may take a while for CI once cu develops. Although shear will be increasing through the day, moisture availability will be a concern for more than LP type supercells, especially as storm move off of higher terrain.
Warning ops – our feeling is that initial warning ops, perhaps through at least 21z, should be centered on mid-atlantic region with the option of shifting west to Colorado eastern plains and western Kansas after 21z for possible initiation of isolated/scattered supercells. Greatest value of satellite CI detection and 3dvar fields may be most useful over eastern ops area, although CI detection along with OUN WRF output could be utilized out west. Expecting mainly a hail threat with the LP-type storms in the Plains, and evaluation of some of the MRMS products would be helpful as well."
Simulated satellite display change
Forecasters and participants within the EFP severe and CI desks suggested to us a change in how we display the simulated satellite products from the NSSL-WRF within the NAWIPS systems. They use the simulated satellite not only to forecast, but also to compare the model output to observed satellite imagery. They noticed that the projection we were providing to them did not match the observed satellite data. They suggested to us that we make the projections more similar to the satellite data... so we did, and here is the before and after...
BEFORE
AFTER
Monday, May 16, 2011
First WES case
Today EWP forecasters participated in our weekly training and are now engaged in a displaced real-time Weather Event Simulator (WES) case for further hands-on training. The event occurred on May 19th 2010 over Oklahoma. The reason we chose this case was because all of the experimental products were available, including PGLM since it was over the OKLMA. The case also gives us the unique opportunity to view storms from initiation all the way through dissipation in a controlled environment, with tornadoes and other severe weather in between. Each forecaster works on their own AWIPS machine to familiarize themselves with the products, how to load them, and also how to best display them. We ask the forecasters to create their own procedures (or preloaded AWIPS displays) and we save them all for further reference. We want to see how the forecasters use the experimental data in combination with other products that are available within AWIPS. This also gives the forecasters the chance to engage the PIs (and vice-versa) with any questions that they may have regarding the products' uses. The hope for this is that by the time we begin real-time operations over the coming days, the forecasters will be ready to use the experimental products confidently.
PGLM Assists in Severe Thunderstorm Warning (Repost)
Animation from 12 May 2011 covering from 2211-2226 UTC. The PGLM flash extent density is on the left with the corresponding radar reflectivity on the right. To see the animation, please click on the image.Today’s afternoon shift started with forecasters working across the Norman, Tulsa, and Little Rock county warning areas. With the some storms beginning to form south and east of Norman, Oklahoma, it was felt this would be a good opportunity to take another look at the PGLM flash extent density observations and focus on total lightning. The PGLM flash extent density was very useful in identifying when the first cloud-to-ground strikes would occur. The PGLM was preceeding the first cloud-to-ground strike by approximately 30 minutes today.
As the the afternoon progressed, the storms began to intensify, both on radar and with the PGLM flash extent density and we shifted from using the PGLM for lightning safety and moved into warning operations. By 2211 UTC on 12 May 2011 (the first image of the loop shown above), three severe thunderstorm warnings were in effect. The area of interest for this post is in between the two existing warnings in the west. At 2211, the PGLM flash extent density was no more than a few flashes per minute. By 2214 UTC the number of PGLM flashes was already approaching 40 per minute. This continued to rapidly increase through 2220 UTC when the PGLM flash extent density observe 82 flashes in a 1 minute interval for a single 8×8 km grid box. This was one of the largest lightning jumps of the day with an increase of 75 flashes per minute in a nine minute time span. With this major lightning jump, along with the forecaster’s interrogation of radar data, a new severe thunderstorm warning was issued at 2226 UTC. This warning was later verified with several severe hail reports.
Total lightning preceeding the first cloud-to-ground strike (Repost)
As we watched the storms move through central Oklahoma today a small, isolated cell developed over Lawton, Oklahoma. This storm conveniently gave us the opportunity to show the effectiveness of total lightning observations in helping gain lead-time ahead of the first cloud-to-ground lightning strike. This small cell turned out to be even more interesting as the PGLM observations gave a 29 minute lead-time over the first cloud-to-ground strike. This was pretty remarkable as the lead time is usually on the order of 5-10 minutes. Below are three images showing the event.
FIGURE 1: A four panel display in AWIPS from 2055 UTC on 11 May 2011. Going clockwise from the upper-left is the radar reflectivity, PGLM flash extent density, PGLM maximum flash density, and NLDN cloud-to-ground lightning strike observations. A single flash just southwest of Lawton (KLAW) can be seen in the PGLM flash extent density and no cloud-ground strikes are observed with the Lawton cell.
FIGURE 2: The same as FIGURE 1, except for the time is 2100 UTC. The PGLM flash extent shows two flashes and the radar reflectivity has strengthened.
FIGURE 3: The same as FIGURE 1, except for the time is 2124 UTC. The radar reflectivity has increased more and the PGLM flash extent density shows several flashes. The NLDN cloud-to-ground lightning observations finally shows a single, negative cloud-to-ground strike just to the northeast of Lawton, Oklahoma. This PGLM gave a tremendous 29 minute lead time on this first strike.
FIGURE 1: A four panel display in AWIPS from 2055 UTC on 11 May 2011. Going clockwise from the upper-left is the radar reflectivity, PGLM flash extent density, PGLM maximum flash density, and NLDN cloud-to-ground lightning strike observations. A single flash just southwest of Lawton (KLAW) can be seen in the PGLM flash extent density and no cloud-ground strikes are observed with the Lawton cell.
FIGURE 2: The same as FIGURE 1, except for the time is 2100 UTC. The PGLM flash extent shows two flashes and the radar reflectivity has strengthened.
FIGURE 3: The same as FIGURE 1, except for the time is 2124 UTC. The radar reflectivity has increased more and the PGLM flash extent density shows several flashes. The NLDN cloud-to-ground lightning observations finally shows a single, negative cloud-to-ground strike just to the northeast of Lawton, Oklahoma. This PGLM gave a tremendous 29 minute lead time on this first strike.
PGLM data and lightning safety (Repost)
Central Oklahoma had several strong thunderstorms move through the region and the forecasters at the Spring Program had the chance to check out the pseudo geostationary lightning products derived from the Oklahoma lightning mapping array. Most of our time was spent investigating the products and discussing the various pros and cons. The figure above shows a good use for these data in a lightning safety perspective. The 1-minute PGLM flash extent density (and the corresponding NLDN cloud-to-ground lightning data) are tightly clustered with the the stronger convective regions, indicated by strong radar reflectivity. However, unlike the NLDN data, the PGLM flash extent density still showed that lightning flashes were extended anywhere from 8-32 km into the stratiform region. This shows the advantage of seeing the spatial extent of lightning activity available from total lightning observations. This is further emphasized with the PGLM maximum flash density in the upper-right which shows the maximum PGLM for each grid box for the past 60 minutes. This shows that most of central Oklahoma has had lightning activity within the past hour, indicating that the threat of a cloud-to-ground strike still exists.
Figure: A four panel display from 2059 UTC on 11 May 2011. The upper-left shows the 1 minute PGLM flash extent density. The upper-right is the 60-minute PGLM maximum flash density while the storm relative velocity is in the lower left and radar reflectivity is in the lower right.
Figure: A four panel display from 2059 UTC on 11 May 2011. The upper-left shows the 1 minute PGLM flash extent density. The upper-right is the 60-minute PGLM maximum flash density while the storm relative velocity is in the lower left and radar reflectivity is in the lower right.
Friday 13 May debrief... finally
Apologies for some lost posts on the blog and the lack of posts since Thursday morning. The Blogspot server went down and we couldn't access it until sometime this weekend. We will be working on restoring some interesting posts about PGLM and SATCAST that got lost. In the meantime, here is a transcript of what we discussed with the EWP forecasters during the end of week debrief...
UWCI / OTTC
- Was not coming in correctly all week, so was not demonstrated within AWIPS.
- Forecasters were not comfortable offering further comments based solely on informal demonstrations with visiting PI since they were not able to use the products within AWIPS.
SATCAST
- I think that does have some utility, but I think the way that it is a yes/no solution doesn’t work. It clearly wasn’t in a position to be used in an operational state with just a yes/no. From visible satellite you can clearly see that there are Cu in the area, but if you have multiple colors for different features of CI it might be very useful.
- From the standpoint of just having more data to compliment the process, I think it would be very useful.
- Looking at “areas” where CI was going to occur versus individual cells was much more useful to me. From the training I was expecting to see individual cells and when I used it I saw way too many false alarms, but once I switch the way I looked at it, it became much more useful.
- When it stayed red, it gave much more confidence than flickering on and off red.
- Having 6 thresholds may have been detrimental because it caused the flickering. Perhaps having some intermediate CI nowcasts would be useful to add.
- I think its strength is going to be its spatial and temporal resolution.
- I think its greatest utility would be in weakly sheared environments… 100’s of Cu over the area and this would help pick out which ones to pay attention to.
- Day/night switch triggered many more false alarms.
- “I think you’re on the right track with what you are doing.”
NEARCAST
- After the training, the forecasters felt comfortable understanding the product and how to use it.
- Color curves seemed to be reversed from NAWIPS/web versus AWIPS, and were confusing, but they worked through it.
- “You can infer convective instability 100 different ways.” … Forecaster was still confused as to how this was showing much more information.
- It is definitely best in the 1-2 hr timeframe, but anywhere outside of that it gets hard to use.
- At one point data did not arrive between 16-21 UTC, made fairly hard to use.
- Issue of clouds… later on in the day there were so many blacked out areas so we couldn’t really see what was happening.
PGLM
- Used the second “jump” as a situational awareness tool and decided to warn on it and it ended up having severe hail (5/12 – Norman). This preceded any radar indicators by 1-2 volume scans.
- I thought it was a good head’s up tool… going into it I didn’t know what to expect, but it ended up getting the storms that had severe just before radar. It was a very good situational awareness tool.
- It did seem that there was a lot more IC than CG yesterday (5/12 - Norman). The CGs were not a good delineator of severe vs. non-severe.
- I would like to see a WES case before getting immersed in the data.
- I definitely saw IC first and then CG, so it definitely provided me with a good heads up tool.
- The 1-minute data was really useful… That was enough resolution for me… 20-30 seconds may be too much. I especially preferred the instantaneous data… I wasn’t really interested in what happened in the past so I didn’t use the max density much.
- An IC-CG ratio product would be very useful.
- “A time-series would be awesome. If I want to interrogate individual cells, I want to dig into it.” … This is in conflict with the overall forecaster feedback last year (and some this year), who did not like the idea… General consensus was that if was not within AWIPS it would not be used… May be something to bring into AWIPS-II
- I don’t know what these values mean yet… If I was to take this back today, I couldn’t even explain what this does. I think you need to explain what a certain value is showing us, otherwise I think you will have a hard time selling this to forecasters.
- Fire weather in the west is obviously a big thing that the PGLM data can help fill the holes by radar and NLDN. There won’t be as much surprise by lightning starts.
OVERALL
- You have to get a large enough group of forecasters comfortable with these products who will go out and spread the word and the spread will become viral.
- “I didn’t find the integration with the CI group helpful, I actually felt more confused with the forecast by going over there. When we come in they have already chosen their domain and I’m not sure how much we can provide to them. The whole time I wanted to go to AWIPS and look at what’s going on. The concept was good, but their mission was different than what we were doing. I could see it being useful for us if we had some time to look at the data and then go over and ask them what they are seeing.”
- Maybe if the morning shift came in at 10 or 11 it might be more useful… The forecasters didn’t seem to find the idea of coming in early useful to adding information for the evening shift.
- Forecasters did not find the large briefing with the EFP useful. It seemed like everyone in the EFP was still working within their own “stovepipe” and that they were just an audience and not participating much.
- Surveys were designed very well and not tedious… having one survey for all products was a great idea.
- Having the PIs around was very helpful because they could ask questions and continue to use the products.
- At the beginning they felt that there were too many projects, but as the week moved on and the PIs sat down and worked with them, it wasn’t too much to handle.
- A WES case at the beginning of the week with all products would help with the exposure to each of the products at least once.
UWCI / OTTC
- Was not coming in correctly all week, so was not demonstrated within AWIPS.
- Forecasters were not comfortable offering further comments based solely on informal demonstrations with visiting PI since they were not able to use the products within AWIPS.
SATCAST
- I think that does have some utility, but I think the way that it is a yes/no solution doesn’t work. It clearly wasn’t in a position to be used in an operational state with just a yes/no. From visible satellite you can clearly see that there are Cu in the area, but if you have multiple colors for different features of CI it might be very useful.
- From the standpoint of just having more data to compliment the process, I think it would be very useful.
- Looking at “areas” where CI was going to occur versus individual cells was much more useful to me. From the training I was expecting to see individual cells and when I used it I saw way too many false alarms, but once I switch the way I looked at it, it became much more useful.
- When it stayed red, it gave much more confidence than flickering on and off red.
- Having 6 thresholds may have been detrimental because it caused the flickering. Perhaps having some intermediate CI nowcasts would be useful to add.
- I think its strength is going to be its spatial and temporal resolution.
- I think its greatest utility would be in weakly sheared environments… 100’s of Cu over the area and this would help pick out which ones to pay attention to.
- Day/night switch triggered many more false alarms.
- “I think you’re on the right track with what you are doing.”
NEARCAST
- After the training, the forecasters felt comfortable understanding the product and how to use it.
- Color curves seemed to be reversed from NAWIPS/web versus AWIPS, and were confusing, but they worked through it.
- “You can infer convective instability 100 different ways.” … Forecaster was still confused as to how this was showing much more information.
- It is definitely best in the 1-2 hr timeframe, but anywhere outside of that it gets hard to use.
- At one point data did not arrive between 16-21 UTC, made fairly hard to use.
- Issue of clouds… later on in the day there were so many blacked out areas so we couldn’t really see what was happening.
PGLM
- Used the second “jump” as a situational awareness tool and decided to warn on it and it ended up having severe hail (5/12 – Norman). This preceded any radar indicators by 1-2 volume scans.
- I thought it was a good head’s up tool… going into it I didn’t know what to expect, but it ended up getting the storms that had severe just before radar. It was a very good situational awareness tool.
- It did seem that there was a lot more IC than CG yesterday (5/12 - Norman). The CGs were not a good delineator of severe vs. non-severe.
- I would like to see a WES case before getting immersed in the data.
- I definitely saw IC first and then CG, so it definitely provided me with a good heads up tool.
- The 1-minute data was really useful… That was enough resolution for me… 20-30 seconds may be too much. I especially preferred the instantaneous data… I wasn’t really interested in what happened in the past so I didn’t use the max density much.
- An IC-CG ratio product would be very useful.
- “A time-series would be awesome. If I want to interrogate individual cells, I want to dig into it.” … This is in conflict with the overall forecaster feedback last year (and some this year), who did not like the idea… General consensus was that if was not within AWIPS it would not be used… May be something to bring into AWIPS-II
- I don’t know what these values mean yet… If I was to take this back today, I couldn’t even explain what this does. I think you need to explain what a certain value is showing us, otherwise I think you will have a hard time selling this to forecasters.
- Fire weather in the west is obviously a big thing that the PGLM data can help fill the holes by radar and NLDN. There won’t be as much surprise by lightning starts.
OVERALL
- You have to get a large enough group of forecasters comfortable with these products who will go out and spread the word and the spread will become viral.
- “I didn’t find the integration with the CI group helpful, I actually felt more confused with the forecast by going over there. When we come in they have already chosen their domain and I’m not sure how much we can provide to them. The whole time I wanted to go to AWIPS and look at what’s going on. The concept was good, but their mission was different than what we were doing. I could see it being useful for us if we had some time to look at the data and then go over and ask them what they are seeing.”
- Maybe if the morning shift came in at 10 or 11 it might be more useful… The forecasters didn’t seem to find the idea of coming in early useful to adding information for the evening shift.
- Forecasters did not find the large briefing with the EFP useful. It seemed like everyone in the EFP was still working within their own “stovepipe” and that they were just an audience and not participating much.
- Surveys were designed very well and not tedious… having one survey for all products was a great idea.
- Having the PIs around was very helpful because they could ask questions and continue to use the products.
- At the beginning they felt that there were too many projects, but as the week moved on and the PIs sat down and worked with them, it wasn’t too much to handle.
- A WES case at the beginning of the week with all products would help with the exposure to each of the products at least once.
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