Verifying yesterdays forecast and comparing to NSSL-WRF lightning threat

1800 UTC 24 August - 1200 UTC 25 August 2011 dry thunderstorm probability forecast with NLDN lightning detections from 0030 (top left), 0450 (top right) and 1150 UTC (bottom) on 25 August 2011.
At the beginning of the experiment today we 'verified' our previous day's forecast for dry thunder over much of the NW US. We had probabilities of dry thunderstorms reaching 40% over much of the area (see images above). When compared to the NLDN observed lightning activity, we see that our higher threat areas (30-40%) matched up fairly well with what occurred. Most of the storms over OR were classified as dry thunder, most likely due to their rapid storm motions. We could have extended our area a little further east to cover central ID (see last image above), which was suggested by the NSSL-WRF total lightning threat. When examining the GOES fire / hotspot detection product to our forecast, we did see a few new starts in the area, with at least one large fire confirmed by observers.

When we compare the observed lightning to that which was forecast by the NSSL-WRF total lightning product, we see that overall the NSSL-WRF tended to slightly downplay some of the lightning activity, but the spatial locations and timing were fairly well forecast (see yesterday's post). This product was developed and validated over the SE US, so the values in the west have yet to be compared directly. Part of this experiment is to get a general idea of how well this product could work over the western US, with the potential for use in operational fire weather forecasts.

Dry thunder over southern Oregon

7-day observed surface dryness (top) and dryness anomaly (bottom) from the GOES-West satellite from 23 August 2011.
Today has the potential to be a fairly significant day for fire weather threat over much of the NW US. GOES-West observed surface dryness and dryness anomaly over the past 7 days (images above) indicates significant drying of potential fuels over much of the western US, with a relative maximum over much of eastern OR and into ID, CA and NV. This agrees well with the observed Predictive Service Area dryness product.

A relatively strong vorticity max for the area is expected to move through this afternoon and bring with it some moderate instability with low PW and surface RH. Storms are expected to track fairly quick, so even if there was a chance of wetting occurring at the surface, the duration would be limited, so the potential for dry thunder is fairly high. Given the good amount of instability, the amount of lightning strikes will be relatively high, which increases the potential for new fire starts. The NSSL-WRF experimental lightning threat output shows this to some degree during the 2300-0200 UTC time periods of the 24th and the 25th of August (see images below).

NSSL-WRF experimental lightning threat for 24-25 August 2011 at 2300 (top left), 0000 (top right), 0100 (bottom left), and 0200 UTC (bottom right).

Examining NSSL-WRF simulated imagery/lightning

Observed (top) and simulated NSSL-WRF (bottom) WV imagery for 1300 UTC on 24 May 2011.
This morning EFP forecasters and scientists examined the simulated satellite imagery and lightning threat products from the NSSL-WRF. One of the most useful aspects of creating simulated satellite imagery from a model is the ability to compare the output directly to observed satellite imagery to determine model performance, as well as being able to have a one-stop 3-D representation of the model produced atmosphere. At 1300 UTC we matched the simulated GOES-R band 9 (6.95 micron) to the observed GOES-13 WV channel to determine model performance for the day. As you see from the images above, the model atmosphere and the observed atmosphere are very similar. The model correctly identifies an MCS over N. KS and on the KY/TN border. It should be noted that the model's simulated cloud tops generally appear to be smaller and less extensive with the cirrus shields. The position of the mid-level jet streak is also very similar, as seen in the deeper red colors extending from AZ/NM/TX panhandle.

NSSL-WRF simulated lightning threat for 2000 UTC (top) and 0000 UTC (bottom) for 24 May 2011
The NSSL-WRF initiates storms between 1900-2000 UTC along the OK/KS border. The simulated lightning threat imagery (seen above) provided by Bill McCaul (USRA) provides us with an estimation of total lightning flashes. At 2000 UTC (top most image), we see the first isolated storm along the border, with total flashes per square kilometer per 5 minutes reaching a value of 5. At 0000 UTC (bottom most image), we can see the extent of the storms across most of OK along the dryline. At this time we can see flash rate values reaching 12 and can start to get an idea of storm tracks.

NSSL-WRF simulated GOES-R low- (top), mid- (center), and high-level (bottom) WV imagery for 0000 UTC on 24 May 2011.
As we continue through time past initiation, we can take a look at the three GOES-R WV channels produced from the NSSL-WRF imagery. Each channel peaks at a different level in the atmosphere, essentially providing us with 3 layers of water vapor measurements. Currently unavailable on our operational GOES satellite, this will be available with GOES-R and we can simulated it using numerical models. What is particularly interesting in this imagery at this forecast time is the presence of a very strong dry signature (red colors) extending from the TX panhandle into central OK in the high-level water vapor (bottom image above). This is an indication of very strong mid-level jet streak. This signature is present in the lower level WV images as well.

Simulated lightning threat over western US for fire weather applications

NSSL-WRF Simulated lightning threat 3 21-hour forecast (contoured) and hourly NLDN lightning detections (red symbols) valid at 2100 UTC on 9 June 2010
Today I spoke with Mark Burger from NWS Eureka, CA who is participating in the EFP this week about the GOES-R products and our future plans for a fire weather and heavy rain experiment. One of his questions regarding the NSSL-WRF simulated lightning threat product particularly peaked my interest. He asked how the lightning threat performs over the west where it would be very useful in fire weather forecasting operations. I pulled up the output from yesterday's 00Z run and overlaid NLDN lightning detections over the OR/WA/ID area for some convection that occurred in the late afternoon. The attached image in this post shows an example of this output for the 2100 UTC time period (a 21-hour forecast), with NLDN lightning detections over the past hour shown as red + or - symbols. The lightning threat product, which predicts total lightning over each square km per 5 mins at the same time captured well the regions of peak lightning interest. This will be a very interesting thing to examine during this year's fire weather / heavy rain experiment taking place this August/September. I passed along the web link for this output, as well as some other GOES-R products, for him to use in the office and distribute amongst other forecasters.

EWP daily briefing... 6/9/2010

Before the official briefing started, one of the forecasters mentioned to Lee Cronce and myself the idea of creating a filter for the CI product where cirrus is present so that the forecasters will know when the product will not be able to make any nowcasts, similar to how the radars have a certain color for areas where range folding is occurring. He mentioned that at some times they cannot understand why the product is not producing nowcasts in obvious situations of CI unless someone looks up the cloud type output for them. This was noted by Lee as a possibility for future input into the product's output.


24-hour thermal couplet detections and severe reports for 7 June 2010
During the briefing Lee presented some scan by scan output from the UWCI product over Wyoming during the 6/7 IOP. He mentioned that the first signal in the UWCI was seen at 2032 UTC, with more widespread signals occurring at 2045 UTC and beyond. The area of interest was actually located between two radars where coverage is fairly limited and the UWCI provided some information on the initiation about 15 minutes prior to detection on radar. He also showed the 24-hour thermal couplet detections and severe reports from the same event (see images above). There were a lot of detections associated with the severe reports, including one that was co-located with and prior to a report of a tornado near Scottsbluff, NE.

One of the forecasters mentioned the possibility of a GOES-R storm top divergence product. He mentioned how this would be very useful in determining storm characteristics in warning operations. I mentioned Bob Rabin's work with current GOES WV winds in producing real-time winds at various levels by tracking features in the WV imagery. From these winds he is able to calculate divergence, vorticity and wind speed contours. I showed them real-time examples from the website provided by Bob Rabin at http://cimss.ssec.wisc.edu/mesoscale_winds/. The forecasters seemed very interested in this and mentioned interest in demonstrating this in future experiments. I also made sure to point out that with GOES-R's great improvement on spatial and temporal resolution, these products will be much more accurate and will be able to capture smaller scale features. I also talked about GOES-R's increased capability for object tracking.

During the weather discussion I showed the forecasters the UW-CIMSS simulated satellite/observed satellite comparison page to see how well the NSSL-WRF was representing the day's weather. It seemed to be doing fairly well so I showed the simulated lightning threat product to see what the NSSL-WRF was showing for the possibility of lightning over the CONUS region. There seemed to be the possibility of some lightning occurring over the Nashville area later on this evening, so following the weather discussion for the day we decided to localize near Huntsville, AL for the possibility of real-time PGLM operations.

EWP daily briefing... The 2345 UTC hour-long satellite gap

At the beginning of the briefing we discussed the previous day's event. Unfortunately due to a few problems we were not able to draw any conclusions from the UWCI or OTTC products from yesterday's event. First, we were not able to display any satellite imagery, so overlaying the UWCI and OTTC products was not possible. Lee Cronce did suggest that we overlay the products on radar towards the middle of the IOP last night, but at this point the second problem came into play... cirrus. During the later half of the IOP the entire region was covered with thin/thick cirrus and thus made the UWCI products inoperable. The OTTC product were still working, but at this point we encountered the hour long void of satellite data from 2345 UTC to 0045 UTC. This hour long void has been causing a lot of trouble during our evening IOPs in the EWP. I have also been hearing complaints from SPC operations as this is a very important time-frame for severe weather and the forecasters don't understand why this time period was selected. Once this occurs we essentially have to shut down the GOES-R aspect of the IOP because the forecasters become disillusioned by the extremely poor temporal resolution of any satellite data during this time period. By the time the satellite data returns, there is no continuity in the products in the forecasters minds and they therefore stick to the radar products they have been comfortable looking at over the past hour. The silver lining from yesterday is that we did see our first thermal couplet detection in real-time last night and it did occur at the time of the issuance of a tornado warning by one of the forecaster groups. In this case it did not provide any lead time, but it did provide confidence in their warning decision.

During the weather briefing I showed the forecasters the NSSL-WRF simulated satellite imagery and lightning threat to help determine the location for tonight's IOP. The forecasters were very interested in the model output and asked to see it every day during the weather briefings. For tomorrow I will also show them the verification page that UW-CIMSS has created for the simulated satellite imagery. We decided to spend the first half of the IOP by splitting the forecasters up into two groups... one participating in a WES case for the PGLM, while the other monitors the location of interest for this evening's IOP for convective initiation. We have decided to localize over Kansas City, MO for the real-time IOP. Updates to follow.

EFP week 3 begins...

Today begins a new week of Spring Experiment activities within the HWT. There were no operations on Monday, hence the lack of posting. Also, the EWP is not operating due to the short week, so there will be a heavier interaction within the EFP this week. This week's visitors include Bill McCaul from the University of Alabama in Huntsville, and Dan Hartung and Chris Rozoff from UW-CIMSS. We will be focusing more on the simulated lightning threat and satellite imagery from the NSSL-WRF this week as those products are more relevant to EFP operations. Given the opportunity, we will also be evaluating the convective initiation and overshooting top / thermal couplet detection products during the afternoon time frames.

Today's focus for the severe and QPF groups in a mesoscale area centered over Omaha, NE. Bill McCaul and Chris Rozoff will be participating in the aviation group today who are focused on an area covering much of the eastern half of the US. Dan Hartung will be working with the QPF group today. The groups will rotate throughout the week. We are already utilizing the CTC product in the aviation group to highlight areas on satellite imagery of future convective development. We have talked about how the current satellite provides some limitations in detection due to the coarse resolution of the IR channels. Steve Silberberg from the Aviation Weather Center (AWC) discussed with Chris Rozoff and I about the possibilities of providing these products at the AWC and I told him we would be happy to help them getting the data into their NAWIPS systems since we have much experience doing this at the SPC.

The simulated satellite imagery was examined by the QPF group, comparing it to actual satellite imagery from the same time. We were able to determine that the NSSL-WRF was showing a good ability at capturing larger scale features such as short-waves and jet streaks. The smaller, more convective scale features were slightly misplaced, especially over the KS/NE area. We discussed the future of our efforts with the simulated model imagery, including providing more model runs and producing GOES-R-like products from the simulated imagery, such as band differences.

EWP daily briefing... 5/27/2010

During the weather briefing we showed the NSSL-WRF lightning threat and simulated satellite imagery since it seemed as though the NSSL-WRF was handling the weather pattern fairly well today. The decision was made to focus over the DC area since there is a slight risk and severe thunderstorm watch out at the time of the briefing, as well as the DCLMA for pseudo-GLM demonstrations. Unfortunately it looks as though the lightning threat decreases fairly rapidly as the storms move south towards the DCLMA network according to the NSSL-WRF lightning threat output, but we hope that we will be able to capture some information.

EWP daily briefing... Model-based product development

Today was the orientation briefing for the NWS forecasters participating in the EWP this week. As part of the briefing we present a short weather discussion where we will ultimately select the region where we will be focused on for the day. Today during the briefing I once again showed the forecasters the NSSL-WRF simulated satellite imagery and lightning threat forecasts and explained how they work. One forecaster asked about generating products from these model data, in particular the 10.7-3.9 channel difference for low cloud and fog. I mentioned that we hope to be developing products from the simulated model output in the future as a proxy for the real products to be available on GOES-R rather than relying on current instruments which may not be able to provide us with the spectral, spatial or temporal we need to produce these products. In addition, Wayne Feltz mentioned that the eventual plan would be to have some sort of real-time rapid updating model forecast imagery to simulate observed satellite imagery and products for use in the Proving Ground.

The plan for the day is to operate over the WFO Dodge City, KS and Amarillo, TX CWA regions and focus on the GOES-R products first while storms are hopefully still initiating to get some feedback from the UWCI and OTTC products while they are most applicable. Unfortunately, at the time of the training, which took up the first half of the EWP day, severe thunderstorms were already ongoing with associated tornado and severe thunderstorm watches all the way from the borders of Canada to Mexico. (see images below) Therefore, getting some quality CI events may be difficult due to expanding cirrus from the already mature convection... updates will be provided as the day progresses.




SPC watches and associated radar reflectivity by 2000 UTC on 24 May 2010

Total lightning IOP plans

At 1:30 PM, the the North Alabama Lightning Mapping Array (NALMA) showed lightning activity along the northern Mississippi-Alabama border. The 00Z 20 May NSSL-WRF run in support of the NSSL/SPC EFP shows continued evolution of this convection toward central Alabama by 00-02Z this evening.

The lightning threat field in the NSSL-WRF using the McCaul blended vertically integrated ice / graupel flux method shows lightning activity extending north-south through Alabama at 1Z. The predicted flash rates are somewhat less over the far northern part of the domain.

An intensive operations period is planned in the EWP over the northern Alabama domain beginning 23Z, where Pseudo-GLM total lightning data derived from the NALMA will be examined along traditional radar-based warning methodology for insight about the location and trends of the most intense updrafts and enhanced threat for severe weather. If the model forecasts verify, we expect the most intense convection over central Alabama with weaker convection over the northern part of the state.

EWP daily briefing... 5/20/2010

EWP 1pm daily briefing on May 20, 2010
Here is some very interesting dialogue from today's EWP 1pm daily briefing. Kris Bedka and Justin Sieglaff posed questions to the forecasters regarding the UWCI and OTTC products and these were they're responses...

In the case of multiple towers with equal weak reflectivities on radar, would CI detection over one and not the other add value to your forecast?

"It's plausible. If that's the way it play out. It would be hard to objective analyze that all the time."

"It does have utility in determining which storm will be the dominant storm."

"Depends on the environment."

When visible satellite is not available, is it (CI detections) even more useful? (this was simulated in yesterday's IOP for one forecaster)

"Yes, absolutely" (also agreed by the other forecasters in theory)

Does a continued signal in CI over one storm provide increased confidence?

"The opposite may be more useful in determining if the storm way dying. It's the end of an event that gives people the most trouble." (forecasters reiterated the need for object tracking)

General discussion on overshooting-tops...

"Overshooting-tops are much more common than I was led to believe in school."

"We did observe that the reflectivity core aloft did intensify when an overshoot was detected."

"Would be interesting to see how they correlate with the occurrence of BWERs. If we had temporal continuity (a continuous) detection, we would expect to see a BWER."

"Overshooting dissipation would be interesting in determining the occurrence of tornado or large hail at the surface."

"If we had rapidly updating satellite, it would be much more useful."

"Might also be useful to have a OT track product... would help in determining storm (updraft) motion."

In addition, we discussed the inclusion of satellite data into an end-to-end tracking system to better compare to radar signatures objectively. It was also noted that next year, it is expected that the EWP will have a more robust AWIPS system that will be able to ingest a total feed (similar to a WFO), that will be on all year that can have new experimental products running on it constantly. This will provide year-round testing of products, rather than a month long experiment. They also plan on having this ready earlier in the year before next year's experiment so dataflow issues are reduced.

We showed the NSSL-WRF simulated reflectivity and lightning threat output for the weather briefing to help decide location for which we would localize the AWIPS stations. Simulated reflectivity showed a large line of storms moving through the area sometime around 00Z. The lightning threat fields showed that the most most lightning activity was expected along the southern edge of the line of storms as the evening progressed. We are hoping that we can see if the addition of lightning data on this southern edge will help determine which areas are the bigger threat during the decision making process for warning along the entire line. Since the storms aren't expected to form in the Huntsville area until the later-half of the EWP IOP, it was decided that we would focus on S. TX for the first half of the day, and then following the dinner break we would switch to Huntsville, AL domain to get some pseudo-GLM demonstration. Will provide updates as they arrive.

EWP ready to go... 5/19/2010

Just got done with EWP's daily afternoon briefing and we have selected to localize over Norman for the day on both teams due to the obvious severe weather threat over the area this evening.

Some notes from the briefing...

1) Localization selection yesterday automatically selected GOES-West for the satellite imagery, which caused us to lose the RSO imagery for the entire IOP... this was noted to the coordinators and should not happen again.

2) Kris Bedka showed a 24-hour verification in the briefing (and earlier in this blog) that OTs did occur in concurrence with severe weather last night and matched the tracks of the severe reports very well.

3) Justin Sieglaff showed us the verification for the NSSL-WRF simulated satellite imagery from the beginning of today and the forecasts match with the current actual imagery from the same time... so we were able to determine that the NSSL-WRF was accurately developing cloud features within its forecasts.

4) The NSSL-WRF lightning threat forecast was shown to the forecasters for this evening and it helped us identify which storms may have stronger updrafts because of their increased lightning output, which we couldn't necessarily determine from the synthetic satellite or radar output.

Will be providing updates as the day progresses...

Up and running...

At the beginning of the day we monitored the SATCAST product to make sure the data delivery was consistent. No problems were observed until the 1915 UTC update when no data arrived. The 1932 UTC data arrived on time, but the 1915 UTC never came in. The rest of the day performed well so we assumed this was a one time issue. More detailed subjective analysis of the product's performance will be noted in the days to come as we have more chances to look at it.

Following the EWP daily briefing at 2pm, we were given the opportunity to show the EWP forecasters the simulated satellite imagery, lightning threat and severe hail probability that are being provided to the EFP participants. We took about a half hour to explain how the products are developed and what they show and the forecasters seemed very interested and would like to seem them prior to the EWP IOP starting at 4pm. Following that, we all participated in the EFP daily briefing, where we again explained the simulated satellite and lightning threat output to the ~35 people in the room. EFP participants, particularly in the aviation forecast team, expressed interest in using at the lightning threat for their forecasts. The severe and QPF forecast teams have already been looking at the simulated satellite imagery.

2000 UTC SPC day-1 outlook
The EWP IOP began immediately following the EFP daily briefing focusing on the area covered by SPC's moderate risk of severe over the TX panhandle and SE CO (see image above). One team acted as the Pueblo WFO, while one acted as the Amarillo WFO. Unfortunately, an abundance of cirrus was over the area, so demonstration of the UWCI and CTC products was extremely limited. The OTTC product was monitored during warning operations and a few detections were seen. Feedback captured from the Pueblo WFO group indicated the OTTC detection provided them with additional confidence in determining the threat of severe within ongoing convection. The Amarillo WFO group did not have any OTTC detections over their area and, once again, back-to-back 30-minute scans around 0 UTC severely affected the ability to evaluate the product. Towards the end of the IOP, GOES-R visiting scientists discussed with the EWP coordinator about delivering satellite data into their WDSSII end-to-end storm tracker to be combined with radar and lightning data to depict the entire life cycle of a convective storm. This would be a valuable tool to work on in the near future.