Today we spent a couple hours soliciting the forecasters for feedback on all of the products that they worked with this week within the EWP. Given the opportunity, I asked the forecasters some follow-up questions based on some observations this week and from yesterday's event, as well as some of their survey responses. Below are the comments from the discussion...
Convective Initiation
- The CIMSS product had pretty good lead time before we actually started seeing lightning of about 45 minutes to 1 hour, only about 15 minute lead time over 35 dBZ echo.
- Later in the events everything became cloud masked.
- Mostly masked with the CIMSS stuff, but UAH was not and we were expecting CI behind the initial line, but nothing went and there were no CI nowcasts made, so that was very good that we weren't getting false alarms.
- There were times when they would have 30 minute lead-times on radar echos, and other times there were no lead-times during the same event.
- I would like to spend some time looking at those products in more my type of environments, like weak shear.
- A probabilistic approach might be more useful than a simple yes/no output. I like the idea of having pre-CI through CI ongoing information.
- "I tended to look at the UAH one more because it was giving me more detections."
- "I found having the masking overlaid was very important... there were times where the CIMSS wasn't showing something but the UAH was and it helped me get an idea of why."
Overshooting-top / Thermal Couplet
- Later on in the evening we saw some detections, but earlier on we could see some enhanced-v and OT signatures in the imagery, but none were detected.
- If you had someone in operations during warning times that was just doing mesoanalysis and telling forecasters that a detection occurred would be very useful... I get too involved with interrogating radar data during warnings.
- Rapid-scan, high resolution satellite data would definitely make this more useful.
- Would like to see an overshooting top collapse product... maybe an alert.
- Only had a chance to look at the icon detections.
Nearcast
- Saw a moisture tongue coming through, but nothing happened.
- Focused primarily on theta-e product, trying to figure out best way to use that... the challenge the day before was that nothing happened, so it's hard to find the values that are more significant... didn't notice any strong signals yesterday, so I didn't really use it.
- Were not able to get the multiple levels in AWIPS... would like to see those.
- "My initial thoughts were that this was no different than looking at the RUC theta-e product... but I do understand that it was nice to have it based on the observations."
- Would definitely like to see this in my home WFO.
Pseudo-GLM
- What could be really useful for forecasters is some training on total lightning activity and how it relates to what's going on within storms.
- Specific numbers for what an intense flash rate is would be helpful.
- We're fairly comfortable with looking at CG activity and what that means, but an IC/CG ratio product would be useful.
- You can get a sense for the trends, especially when significant, but there's a lot of complexity when looking at the entire storm with some areas decreasing and increasing rapidly within the same cell. Maybe if you could interrogate the storm and get a graph of the total lightning activity.
- We have a lot of users like golf courses and parks that we may not be paying attention to, especially for lightning safety in stratoform rain regions where people may think that it's just light rain. When I'm in warning operations, I get engaged in the base radar data and pay less attention to everything else. This may help a lot in those situations.
Overall
- If we had it set up that one person was in charge of the warnings and looking at the radar data, then the other person could focused on a couple of the experimental products if you're working in pairs at the same desk. If the other desk could do the same thing with a couple of the other experimental products, we might be able to get more useful information on everything.
- "Maybe if we had a couple hours each day to just focus on one product, so all of the fields in the product could be examined. I know I set up a real quick procedure on the first day and only got to look at a couple of the fields and felt like I left the rest behind."
- "I'm wondering if a 2-week period would be better for each forecaster... the first week could be used to get comfortable with all of the products and then the second week we could really get into the products in warning operations." (Difficult to get a forecaster away from their office for 2-weeks... especially in May.)
- If forecasters had a week or two to go through articulate presentations prior to arriving that would help us hit the ground running on the first day and avoid powerpoint death. Make it a prerequisite then have a short discussion with the PIs on what they want to focus on during the first day and go into short DRTs for each product.
Friday, May 20, 2011
Thursday, May 19, 2011
Active CI along dryline continues...
CI continued along the dryline in eastern Oklahoma into southern Kansas continued for several hours on the afternoon of 19 May 2011. The SATCAST CI Nowcasting algorithm provided ~15-45 min lead times for the occurrence of 35 dBZ echoes with several storms. With the lack of cirrus clouds, individual cumulus clouds could be monitored as they developed into (at times) long-lived supercells which produced tornadoes.
Shown is the SATCAST CI nowcast at 2002 UTC (top image, with 2000 UTC surface observations), with the dryline and four CI locations highlighted. Also, a 4-panel radar image set (from 2018-2100 UTC) with the actual CI locations shown, with approximate lead times on CI provided, as subjectively determined. HWT forecasters found these nowcasts valuable as they were able to determine quickly that CI along the dryline was continuing and would be for the coming ~1 hour past the nowcast time of 2002 UTC. The environment on this day was accompanied by ~2500-2700 Jkg^-1 CAPE values, especially in areas further south along the dryline into far northern Texas. The high CAPE values imply a lower lead time on CI in general, as cumulus clouds grow very rapidly between 15-min time resolution images. Having 5-min GOES data will substantially improve our ability to provide more timely CI nowcasts.
Busy CI day in Northeastern U.S.
On 18 May 2011, CI was occurred in many locations in Virginia, West Virginia, far northern North Carolina, and southern Pennsylvania. Shown is the SATCAST CI nowcast at 1730 UTC, with radar images between 1730 and 1817 UTC. Annotated on the SATCAST image are the "CI locations" labeled (a)-(k). On the radar time series, the same regions are highlighted. In the lower right image of the radar sequence, on the 1817 UTC image, are the locations (circled or with an arrow pointing to where the CI event occurred), and the approximate lead times (in minutes) that SATCAST provided. These are subjectively determined. Events where no CI event was observed (a follow-on echo of 35 dBZ intensity) are labeled as "F" for "false alarm."
This event/time period shows how SATCAST performs in a situation in which CI was widespread. It remains challenging for a forecaster to identify exactly where a CI event forms related to a given CI nowcast despite the high number of SATCAST CI nowcasts. In this case, the flow was southerly and hence all CI events occurred to the north (or north-northwest) of a nowcast location. These storms were generally low-topped (25,000-30,000 ft), directly associated with a closed upper low circulation.
Elevated "convective initiation" in a dry environment
One challenge is nowcasting convective initiation when it occurs within environments which are very dry, and/or when the convection is substantially elevated from surface-based heating, leading to convective clouds which fail to produce echoes of 35 dBZ intensity at ground level. In these instances, a CI nowcasting algorithm that identifies this convective development technically fails as the traditional radar-based CI definition of a 35 dBZ echo (whether at ground level or at the altitude of the -10 C isotherm) is never met. Yet, convective clouds do in fact grow to produce rainfall. This leads to the notion that "you know it when you see it" in terms of CI, but in these situations a hard radar-based definition is less easy to follow.
In this example, the SATCAST (proxy Official AWG CI Algorithm) flagged a cluster of cumulus clouds at 1845 UTC, which are seen in 1 km GOES-13 visible satellite data at 1932 UTC. The first radar echo was seen near 1924 UTC with a maximum dBZ of <20 dBZ. This small cell developed over the Plains, and propagated north-northeatward (to the northeast of Trinidad, CO), and maintained only 10-20 dBZ rainfall. Radar data are shown through 2000 UTC. Also shown is the RUC sounding for near this location which confirm (a) the storm occurred in a dry easterly flow, to the north of a warm from, (b) most unstable CAPE values were near 471 Jkg^-1, and (c) cloud bases were near 680 hPa, with storm tops perhaps reaching ~300 hPa (i.e. it was elevated convection).
This example highlights the sensitivity of the SATCAST algorithm for identifying CI in less than obvious situations (when CAPE values are not high, and when cumulus updraft widths do not necessarily fill a 4 km^2 GOES pixel).
pGLM realtime comparison with MESH and 3D-Var Updraft
Repost from EWP blog...
With warning operations already underway for western Oklahoma, forecasters are deep into their storm analysis.
One of the more interesting features they have been picking up on is the consistent signals between the pGLM lightning trends and values from the MESH (Maximum Expected Size of Hail) algorithm as well as the 3D-Var derived updraft fields.
This was well illustrated by the storm north of Elk City moving from Beckham to Roger Mills county. At approximately the same time ~1900-1915 UTC, the lightning rate increased from 5 to 15 flashes per min (per pGLM grid box, not per storm) as MESH ramped up and updraft increased within the 3D-Var product. Shortly after this increase, both the pGLM and MESH values decreased with this storm (the 3D-Var updraft values also showed this, but with a bit of a time lag).
pGLM flash density and MESH values at 1910 UTC on 19 May 2011
Also of note, prior to losing NLDN data, with the storms seemed to be producing relatively little CG lightning. In this case, the pGLM data was definitely giving a better view of the electrical activity and storm intensity. (1 to 1.75 in hail has already been reported across West and SW Oklahoma).
-K. Kuhlman (pGLM scientist, week 2)
With warning operations already underway for western Oklahoma, forecasters are deep into their storm analysis.
One of the more interesting features they have been picking up on is the consistent signals between the pGLM lightning trends and values from the MESH (Maximum Expected Size of Hail) algorithm as well as the 3D-Var derived updraft fields.
This was well illustrated by the storm north of Elk City moving from Beckham to Roger Mills county. At approximately the same time ~1900-1915 UTC, the lightning rate increased from 5 to 15 flashes per min (per pGLM grid box, not per storm) as MESH ramped up and updraft increased within the 3D-Var product. Shortly after this increase, both the pGLM and MESH values decreased with this storm (the 3D-Var updraft values also showed this, but with a bit of a time lag).
Also of note, prior to losing NLDN data, with the storms seemed to be producing relatively little CG lightning. In this case, the pGLM data was definitely giving a better view of the electrical activity and storm intensity. (1 to 1.75 in hail has already been reported across West and SW Oklahoma).
-K. Kuhlman (pGLM scientist, week 2)
CI along the Sea Breeze southwest of Miami
The SATCAST CI algorithm provided a ~45-51 minute lead time to the first occurrence of 35 dBZ echoes near Homestead, Florida (southwest of Miami). Shown are the 1745 and 1815 UTC SATCAST CI nowcasts on 18 Ma7 2011 (the missing image caused by the GOES full disk scan at 1800 UTC). Composite reflectivity for 1749, 1836 and 1900 UTC verify the new convective rainfall that SATCAST first identified as developing cumulus clouds (see circles on images). Ongoing light rainfall near Miami, and scattered across far southern Florida, between 1749 and 1900 UTC is below 35 dBZ intensity and was not that nowcasted by SATCAST.
PGLM products in AWIPS
Forecasters are now examining the PGLM products within their AWIPS workstations during warning operations with several storms over SW OK. The forecasters have created a 4-panel display that contains the 3 current PGLM products we are providing within the EWP, as well as the traditional radar reflectivity and NLDN detections (see image above). The forecasters currently have access to an instantaneous flash extent density (top right corner), a 60 minute sum (bottom left corner) and a 60 minute max track (bottom right corner). We are also working on providing the forecasters with a flash initiation density product, which will hopefully be available next week.
First CI of the day...
So unlike yesterday, activity has not waited and is currently ongoing and the EWP has began warning operations over the OUN CWA where a tornado watch has been issued at 1803 UTC. Forecasters were monitoring the GOES-R CI products throughout the morning following the issuance of their initial AFD. A line of cumulus formed along a dryline extending through western OK down into TX. At 1702 UTC, UWCI flagged a towering cumulus cloud for "pre-CI growth" (see image below) near the TX/OK border. SATCAST did not flag this storm and at this time radar reflectivity had already exceeded 35 dBZ for this particular storm (see image below). It is likely that the storm initiated between the 15 minute scan period from 1645 UTC and 1702 UTC. UWCI continued to flag this storm during the 1715 UTC scan for "CI ongoing". Also at 1715 UTC, SATCAST flagged a storm just north of the initial storm which continued to form a 35 dBZ echo at 1754 UTC, providing a 39 minute lead time on radar. The southern initial storm had it's first CG flash at 1800 UTC, providing about an hour lead time for the first occurrence of CG for the UWCI.
4-panel CI display (top) and radar reflectivity (bottom) for 1702 and 1707 UTC respectively.
4-panel CI display for 1715 UTC
Unfortunately, as it always seems, we lose satellite data for a 30 minute gap during initiation period, so the EWP forecasters have moved into warning operations using radar data as storms continue to develop northward along the dryline. Hopefully at some point this afternoon/evening we will get a chance to examine the overshooting-top and thermal couplet products in warning operations, as well as the PGLM as the storms move a little further east into the OKLMA domain.
Unfortunately, as it always seems, we lose satellite data for a 30 minute gap during initiation period, so the EWP forecasters have moved into warning operations using radar data as storms continue to develop northward along the dryline. Hopefully at some point this afternoon/evening we will get a chance to examine the overshooting-top and thermal couplet products in warning operations, as well as the PGLM as the storms move a little further east into the OKLMA domain.
Simulated satellite imagery
The Convective Initiation group compared simulated ABI and current GOES water vapor imagery to examine the dry line over Texas and western Oklahoma and to evaluate the performance of the NSSL-WRF through early morning. The presence of lee waves downstream of the mountains in extreme southwest Texas was noted on the imagery. Overall, the NSSL-WRF accurately depicted most of the large-scale features, with the usual differences in the locations of individual cloud and convective features. The simulated imagery indicates that convective initiation will occur later in the day along the dry line from south-central Kansas to north Texas. The dry line was also evident in the mid-level (band 9) water vapor imagery prior to convective initiation.
-Jason Otkin
-Jason Otkin
Wednesday, May 18, 2011
Oklahoma CI 18 May 2011
Forecaster comments reposted from EWP blog...
"2330Z Update: UAH CI indicating possible development across Garvin and McClain counties. There does appear to be an HCR in this location but we believe that the edge of thin cirrus clouds are causing algorithm to detect cloud cooling that is not real. Looks like we are going to move operational area to eastern Colorado where there is a lone supercell. kbrown
2230Z Update: Got a hit off of the UAH CI over southern Comanche county where there are weak echoes aloft (15-20dbz). These echoes are associated with a wildfire plume, however.
2140Z: Brief UAH CI detected across north-central Oklahoma in cloud streets (1832Z), but no subsequent echoes were detected.
Although there has been several hours of cu/tcu formation near and east of dryline, CI algorithms have not detected CI across OUN domain. From 20Z to 2115Z this is actually a good thing since no echoes have developed (good case of low false alarm). Before the CIMSS CI became contaminated with Ice Cloud Mask, there were a few hits for CI on leading edge of incoming cirrus across northwest Oklahoma between 19Z to 20Z. No echoes were subsequently detected.
Isolated CI hits from the UAH algorithm did accurately depict some elevated echoes over the OK/AR border but no lightning occurred. Leadtime for echoes was 15 to 30 minutes."
kbrown
"2330Z Update: UAH CI indicating possible development across Garvin and McClain counties. There does appear to be an HCR in this location but we believe that the edge of thin cirrus clouds are causing algorithm to detect cloud cooling that is not real. Looks like we are going to move operational area to eastern Colorado where there is a lone supercell. kbrown
2230Z Update: Got a hit off of the UAH CI over southern Comanche county where there are weak echoes aloft (15-20dbz). These echoes are associated with a wildfire plume, however.
2140Z: Brief UAH CI detected across north-central Oklahoma in cloud streets (1832Z), but no subsequent echoes were detected.
Although there has been several hours of cu/tcu formation near and east of dryline, CI algorithms have not detected CI across OUN domain. From 20Z to 2115Z this is actually a good thing since no echoes have developed (good case of low false alarm). Before the CIMSS CI became contaminated with Ice Cloud Mask, there were a few hits for CI on leading edge of incoming cirrus across northwest Oklahoma between 19Z to 20Z. No echoes were subsequently detected.
Isolated CI hits from the UAH algorithm did accurately depict some elevated echoes over the OK/AR border but no lightning occurred. Leadtime for echoes was 15 to 30 minutes."
kbrown
A Visit By Don Berchoff
Reposted from EWP blog...
"As we waited agonizingly for convection to initiate in our Central Oklahoma Domain (and as of this writing, we are still without storms), we were paid a visit by Don Berchoff, Director of the NWS OS&T."
"Our discussion with Mr. Berchoff included:
- the need to continue improvements in Convective Initiation (both sensor and model based)
- using multi-sensor blending for more holistic storm interrogation
- his thoughts on the coming of AWIPS2 and the utility for extensibility
- the need for improved analysis and visualization tools in light of the 12 fold increase in data flow
“Fortunately” the weather “cooperated” with us and everyone in the room was able to engage in the discussion."
-K. Manross :: Week 2 EWP Weekly Coordinator
"As we waited agonizingly for convection to initiate in our Central Oklahoma Domain (and as of this writing, we are still without storms), we were paid a visit by Don Berchoff, Director of the NWS OS&T."
"Our discussion with Mr. Berchoff included:
- the need to continue improvements in Convective Initiation (both sensor and model based)
- using multi-sensor blending for more holistic storm interrogation
- his thoughts on the coming of AWIPS2 and the utility for extensibility
- the need for improved analysis and visualization tools in light of the 12 fold increase in data flow
“Fortunately” the weather “cooperated” with us and everyone in the room was able to engage in the discussion."
-K. Manross :: Week 2 EWP Weekly Coordinator
Potentially missed CI target... but with a silver lining
As we have seen over the past couple years during the Spring Experiment, the bane of the satellite community's existence has struck again. It's 2100 UTC and that means we have another 30 minute gap in satellite data right during initiation period... so any updates in the imagery and the CI products will have to wait until after 2115 UTC, and our last image was at 2045 UTC. During that period the cirrus is likely to move over the area, inhibiting any of the CI products from detecting the clouds underneath... We will continue to monitor the area, however it seems like we may have just missed our target.
However, there is a silver lining to this event. Forecasters have been watching the CI products constantly over the past couple hours and have noticed no false alarms over the area of developing cu field for either of the CI products. There were a few false alarms with the cirrus overrunning the surface causing false cooling with the UWCI, as well as a couple false alarms with some of the stratus area in eastern CO with the SATCAST (UAH CI) product. The forecasters mentioned that the fact that these CI products were showing no signals over the cu field of interest provided them with increased confidence that CI was NOT occurring. Increased confidence is a good thing, whether it leads to exciting weather or not.
However, there is a silver lining to this event. Forecasters have been watching the CI products constantly over the past couple hours and have noticed no false alarms over the area of developing cu field for either of the CI products. There were a few false alarms with the cirrus overrunning the surface causing false cooling with the UWCI, as well as a couple false alarms with some of the stratus area in eastern CO with the SATCAST (UAH CI) product. The forecasters mentioned that the fact that these CI products were showing no signals over the cu field of interest provided them with increased confidence that CI was NOT occurring. Increased confidence is a good thing, whether it leads to exciting weather or not.
Monitoring CI over OK...
EWP NWS forecasters have begun real-time operations within the HWT. We are focusing on the UWCI, UAH CI, and Nearcast products over the domain waiting for convection to develop along a dryline extending from central OK down across the Red River. An area of cumulus clouds have begun to form along the dryline and we are waiting for further development. An area of thin cirrus (our worst enemy) is moving in rapidly from NM and will eventually impede upon our ability to detect CI from the satellite based products (see image below). We are hoping that CI will occur prior to the cirrus entering the area. Below is an example of what we are looking at, with the UWCI and ice cloud mask overlaid on visible satellite imagery. A false alarm has occurred due to the thin cirrus being misclassified by the cloud typing algorithm and created a false cooling event as it passed over land.
The EFP is also monitoring CI on the CI desk and have been looking at the Nearcast product extensively over the area. They have noticed that the Nearcast has been showing a band of moisture and increased instability potential aligning itself with the dryline and then being advected quickly east. They are concerned that if this area of moisture and instability moves too far east before CI occurs that the potential for any severe convection will be limited. I explained to them that the RUC winds may not be truly representative of what will really happen and to monitor the new forecast that came in at the top of the hour to see if this trend continues.
The EFP is also monitoring CI on the CI desk and have been looking at the Nearcast product extensively over the area. They have noticed that the Nearcast has been showing a band of moisture and increased instability potential aligning itself with the dryline and then being advected quickly east. They are concerned that if this area of moisture and instability moves too far east before CI occurs that the potential for any severe convection will be limited. I explained to them that the RUC winds may not be truly representative of what will really happen and to monitor the new forecast that came in at the top of the hour to see if this trend continues.
EWP daily briefing... 18 May
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.
"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.
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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