Here are some important bullet points from this week's EWP debrief...
UWCI and Cloud-top Cooling
- Forecasters wondering how well it will work in the Northeast... so often cirrus is in the area... Saw very few signals for yesterdays case.
- A little ahead of total lightning with yesterday's case... not like case event when it occurred at same time
- Cloud-top cooling more valuable for situational awareness than CI
- "Wonder if this type of product would be useful in something like guardian or alert type software, because not all people will be looking at it all the time."
- "Would be neat to look at if it saved all the locations where CI was occurring... would like to have the 60-min accumulated.. make it more like the hail tracks" (mentioned this was available)
- "I was watching a storm over Amarillo with 60+ dBZ after CI and there was no CG... I was waiting for lightning to happen because that's what we were told the research used to verify it... You can't use CG as a discriminator... you need total lightning."
OTTC
- All week continued to lag radar signals of severe.
- No thermal couplets saw in real time all week
- Forecasters understand it should work better with 2 km data.
- Similar comment a UWCI about accumulated product
- Overall was not very useful in warning operations.
Pseudo-GLM
- During real-time it was used a little bit, but the events were not as significant (37 flashes/2 min vs over 100 flashes/2 min in archive case)
- "What do these numbers mean?" training needed... need to see it several times over the summer to get used to it.
- "Might be useful to have a grad student or someone track particular features in radar with lightning flash rates to make some correlations... In theory you saw increases in reflectivity with jumps in lightning rates."..."You would have to prove to me that this jump rate is a precursor to tornado occurrence before I would be willing to use it in operations... more research."
- Regarding archive case... lightning jumped way up 5 mins before lightning... dropped significantly as tornado occurred.
- Need for trends (like a max VIL) noted... then they don't have to sample the whole thing every scan... Eric Bruning showed Schultz et al. 2009 work... Also mentioned flash rate trend swath... "Let's do that for next year, I would love to see that."
- 8km resolution made hard to see individual updraft areas... smoothing looked nice and confused forecasters making them think it was higher resolution, but in fact it was removing the peaks.
- "That's a neat product, but by having 1km visible and 0.5km visible on GOES-R, having an 8km product seems like it wouldn't provide as much information as we could be getting from other sources."
- Noticed that when it came to warning decisions, forecasters went straight to standard radar tools (reflectivity tilts, velocity)... "It's what we're trained to do... it's the best tool for those things."
- Issue with identifying polarity for flashes... Told that you can compare NLDN to the GLM
- May be more of an aviation, winter weather thing... "I see it really useful for convective snow events for picking up areas of convective snow."... "Winter storms are more costly for our area." Felt comfortable throwing in winter weather archive cases in Spring if necessary.
Overall / Training
- Felt very comfortable with using the products off the bat... "Eventually as the week progressed, I had my 4-panels set for the products that I found more useful to me."
- "Need a thorough review of how you come up with the values for these data."
- "I think you will find few forecasters that will readily abandon base data interpretation."
- "Try to make the experiment as real as possible as we would experience in the WFO... give us what we're used to."
- "Do more WES cases... don't go into real-time ops for marginal severe events... but it was nice to have live data since we didn't know what or if anything was going to happen."
- "Having some pre-set procedures would be good"
- "Maybe having a checklist would be good to make sure we check out all the products."
- First day come in early and do training day... felt like they were doing "hurry up and wait"
Friday, May 28, 2010
SATCAST within the GOES-R Proving Ground
Over the past two weeks, SATCAST has been brought into the Hazardous Weather Testbed for evaluation by the University of Alabama in Huntsville, the developer of the GOES-R Algorithm Working Group Convective Initiation (CI) algorithm. John Walker and myself have participated in the Experimental Forecast Program and we have learned a great deal on how to best prepare the CI algorithm for forecaster use and prepare for GOES-R.
Over the past two weeks, the SATCAST algorithm performed very well with average lead-times ranging from 15 to 45 minutes. In high CAPE environments, the algorithm was more diagnostic, however, GOES-R will be able to give high temporal trends to allow for more frequent cloud-top trends and give more lead-time for the algorithm. There were some things learned that need some improvement and we plan to work on those weaknesses over the coming months.
Thursday, May 27, 2010
Graphical plots of lightning trends
In our evaluation of the 24 May 2008 archive case today, forecasters highly recommended implementation of a gridded map display of lightning trends in addition to counts. The idea is as follows:
Work by Schultz et al (2009) has shown the applicability of a two-standard-deviation jump of the flash rate derivative above a running mean as predicator of hail, wind, and tornado events. About a year ago, I prototyped a visualization of a cell-entity plot that could graphically show how close the current flash rate was to being considered a lightning jump. These data are courtesy Chris Schultz, for a case from July 16, 2007.
In the video below, the top two panels show time versus (top) flash rate) and (bottom) the flash rate derivative with respect to time (DFRDT), and various threshold- and standard deviation-based thresholds for lightning jump. The bottom panel shows a plan view of a thunderstorm cell colored according to the ratio of DFRDT to the 2-sigma trigger (thick blue line vs. pink line). Yellow colors show that the cell is fliriting with jumping, and the discontinuity to red in the color scale at a ratio above 1.0 calls attention to the jump without requiring an additional symbolic flag.
A real storm cell derived from the WDSSII k-means tracking approach would have a non-circular entity shape, which would obviously be much more realistic than the simplistic circle used here. This demo doesn't show the swath idea, but it is clear that it could definitely improve awareness of flash rate trend history at a glance.
Also, a forecaster just suggested to me that a plot of IC:CG ratio would be interesting, perhaps implemented on a cell basis like the trend plot discussed above. He noted interest in continued availability of the NLDN ground strike (and polarity) data.
Reference:
Schultz, C. J., W. A. Petersen, and L. D. Carey, 2009: Preliminary development and evaluation of lightning jump algorithms for the real-time detection of severe weather. J. Appl. Meteor. Climatol., 48, 2543–2563.
Need to have trend plots, because it's too hard to figure out by querying flash count grids. The forecasters preferred a gridded plan view / map mode (not a line graph), and either a plot of (1) the flash rate derivative or, in the lightning jump sense, (2) the number of standard deviations (possibly fractional, e.g., 1.5) relative to the running mean. This could be implemented using the WDSSII k-means cell shape colored according to the above trend metrics. 30 min time lapse trend swath would also be helpful.
Work by Schultz et al (2009) has shown the applicability of a two-standard-deviation jump of the flash rate derivative above a running mean as predicator of hail, wind, and tornado events. About a year ago, I prototyped a visualization of a cell-entity plot that could graphically show how close the current flash rate was to being considered a lightning jump. These data are courtesy Chris Schultz, for a case from July 16, 2007.
In the video below, the top two panels show time versus (top) flash rate) and (bottom) the flash rate derivative with respect to time (DFRDT), and various threshold- and standard deviation-based thresholds for lightning jump. The bottom panel shows a plan view of a thunderstorm cell colored according to the ratio of DFRDT to the 2-sigma trigger (thick blue line vs. pink line). Yellow colors show that the cell is fliriting with jumping, and the discontinuity to red in the color scale at a ratio above 1.0 calls attention to the jump without requiring an additional symbolic flag.
A real storm cell derived from the WDSSII k-means tracking approach would have a non-circular entity shape, which would obviously be much more realistic than the simplistic circle used here. This demo doesn't show the swath idea, but it is clear that it could definitely improve awareness of flash rate trend history at a glance.
Also, a forecaster just suggested to me that a plot of IC:CG ratio would be interesting, perhaps implemented on a cell basis like the trend plot discussed above. He noted interest in continued availability of the NLDN ground strike (and polarity) data.
Reference:
Schultz, C. J., W. A. Petersen, and L. D. Carey, 2009: Preliminary development and evaluation of lightning jump algorithms for the real-time detection of severe weather. J. Appl. Meteor. Climatol., 48, 2543–2563.
First real-time pseudo-GLM images on AWIPS
Above is the first real-time image we have seen from the psuedo-GLM product over the DCLMA at 2104 UTC. We are currently participating in a real-time IOP over the region due to the severe weather threat and a few severe thunderstorm warnings have already been issued by the forecasters who are localized over State College, PA and Philadelphia, PA.
EFP daily map discussion
Today's EFP map discussion included some very interesting interactions regarding GOES-R. Bruce Entwistle from the Aviation Weather Center who was participating in the EFP's aviation forecast group brought up their afternoon forecast on a loop of visible satellite imagery with cloud-top cooling rates overlaid during the briefing. He described how the cloud-top cooling rates helped focus them on area of interest for deepening convection and helped them nudge their forecast outlook lines slightly. He said that he was seeing rates exceeding 22 K/15-min at some times. He noted that for this sort of application where they are expected to issue their forecasts hours in advance, the cloud-top cooling and convective initiation products may not be as useful, but regional forecast facilities that are required to issue more short term forecasts may find this invaluable.
Louie Grasso brought up a separate discussion regarding the fire activity up north of Montreal, Canada. He talked to the participants about how the 3.9 micron channel was able to detect fire hotpots and showed a very good example of that in real-time over Canada. He mentioned how since GOES-R will have higher spectral resolution, we will be better able to determine the intensity and distribution of the fires. He pointed out that the smoke plumes associated with these fires were hard to distinguish from the clouds around them, and may even become hard to see at all when the sun angle is high since they can be very thin. He told the participants that when GOES-R is available, additional visible and near-IR channels will be able to distinguish different cloud and aerosol types through techniques such as RGB composites. He also pointed out to the participants that the 3.9 micron channel was composed of a reflected and emitted component and showed them an example of a MCS during day and night hours, which showed the cloud tops "cooling" substantially during the switch from night to day. Since the reflected solar component of the 3.9 micron channel is very sensistive to ice particles, the cloud seem's "cooler" when the sun is up. The participants seemed very interested in this and seemed to capture their interest into the wide variety of uses of satellite data outside of visible and IR images alone.
Louie Grasso brought up a separate discussion regarding the fire activity up north of Montreal, Canada. He talked to the participants about how the 3.9 micron channel was able to detect fire hotpots and showed a very good example of that in real-time over Canada. He mentioned how since GOES-R will have higher spectral resolution, we will be better able to determine the intensity and distribution of the fires. He pointed out that the smoke plumes associated with these fires were hard to distinguish from the clouds around them, and may even become hard to see at all when the sun angle is high since they can be very thin. He told the participants that when GOES-R is available, additional visible and near-IR channels will be able to distinguish different cloud and aerosol types through techniques such as RGB composites. He also pointed out to the participants that the 3.9 micron channel was composed of a reflected and emitted component and showed them an example of a MCS during day and night hours, which showed the cloud tops "cooling" substantially during the switch from night to day. Since the reflected solar component of the 3.9 micron channel is very sensistive to ice particles, the cloud seem's "cooler" when the sun is up. The participants seemed very interested in this and seemed to capture their interest into the wide variety of uses of satellite data outside of visible and IR images alone.
24 May 2008 Archive Pseudo-GLM: More feedback
Today two new forecasters will examine the 24 May 2008 Oklahoma LMA case that was also done yesterday.
See the end of this post for several concrete recommendations of enhanced plot types suggested by the forecasters.
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A first reaction from the first few frames of total lightning data: Learning curve associated with the change from ground strike lightning data to total lightning data. The larger flash rates require recalibration on what rates are typical.
18:05 - Weakening trend noted in both ground and cloud flash rates. Down to 18/min in Psuedo-GLM. Also tracking total flash rates vs. 50dBZ height.
Request for max flash rate display (like 88D max dBZ readout) - reduces clicks / exploration to get readout.
18:22 - Starting trend back up in lightning, up to 26/min peak.
"If this comes in every minute, it will definitely beat the radar, since we can spot strengthening/weakening trends prior to the radar data." Conducting real-time test of the that hypothesis via the 50 dBZ comparison.
Again noting dropouts in the archived CG and LAPS data.
"Anything that can give me a few minutes of extra time, I want it. Give it to me." - referring to the total lightning data. Has been switching back and forth between lightning and radar, and carefully monitoring every lightning frame.
18:46 - Southern cell initiated, seen in satellite cooling trends and elevated weak reflectivity core prior to ocurrence of lightning. Explained that since lightning requires precipitation-sized ice, this is expected, but is helpful in tracking stages of convective initiation through mature thunderstorm.
18:28 - up to 53/min
19:00 - SVR issued on both storms
19:08 - Lightning in second cell noted as catching up to the first
Again it seems that once the warning issuance process has begun, radar interrogation occupies most of the forecaster screen time. The radar provides evidence of the actual physical manifestation of hail, so this is more worthy of time than a secondary indicator of convective strength in a less-specific sense.
Might consider using sparklines(miniature trend lines displaced slightly from the cell center, with peak and minimum label values) as a low-impedence way to do non-context-switched examination of total lightning trends.
19:19 - "Broad rotation the whole time in northern storm, but hasn't tightened up."
Near the end of the case, lightning was noted as perhaps being more important in pulse storm situations where lightning would be more clearly indicative of important updraft fluctuations. Not so helpful in this sort of case, with little indication in lightning relative to the specific tornado times (or hail presence, which was already well-determined by radar). But great as situational awareness (like MESH) in making sure no dangerous cells are being missed.
Need to have trend plots, because it's too hard to figure out by querying flash count grids. The forecasters preferred a gridded plan view / map mode (not a line graph), and either a plot of (1) the flash rate derivative or, in the lightning jump sense, (2) the number of standard deviations (possibly fractional, e.g., 1.5) relative to the running mean. This could be implemented using the WDSSII k-means cell shape colored according to the above trend metrics. 30 min time lapse trend swath would also be helpful.
See the end of this post for several concrete recommendations of enhanced plot types suggested by the forecasters.
-------
A first reaction from the first few frames of total lightning data: Learning curve associated with the change from ground strike lightning data to total lightning data. The larger flash rates require recalibration on what rates are typical.
18:05 - Weakening trend noted in both ground and cloud flash rates. Down to 18/min in Psuedo-GLM. Also tracking total flash rates vs. 50dBZ height.
Request for max flash rate display (like 88D max dBZ readout) - reduces clicks / exploration to get readout.
18:22 - Starting trend back up in lightning, up to 26/min peak.
"If this comes in every minute, it will definitely beat the radar, since we can spot strengthening/weakening trends prior to the radar data." Conducting real-time test of the that hypothesis via the 50 dBZ comparison.
Again noting dropouts in the archived CG and LAPS data.
"Anything that can give me a few minutes of extra time, I want it. Give it to me." - referring to the total lightning data. Has been switching back and forth between lightning and radar, and carefully monitoring every lightning frame.
18:46 - Southern cell initiated, seen in satellite cooling trends and elevated weak reflectivity core prior to ocurrence of lightning. Explained that since lightning requires precipitation-sized ice, this is expected, but is helpful in tracking stages of convective initiation through mature thunderstorm.
18:28 - up to 53/min
19:00 - SVR issued on both storms
19:08 - Lightning in second cell noted as catching up to the first
Again it seems that once the warning issuance process has begun, radar interrogation occupies most of the forecaster screen time. The radar provides evidence of the actual physical manifestation of hail, so this is more worthy of time than a secondary indicator of convective strength in a less-specific sense.
Might consider using sparklines(miniature trend lines displaced slightly from the cell center, with peak and minimum label values) as a low-impedence way to do non-context-switched examination of total lightning trends.
19:19 - "Broad rotation the whole time in northern storm, but hasn't tightened up."
Near the end of the case, lightning was noted as perhaps being more important in pulse storm situations where lightning would be more clearly indicative of important updraft fluctuations. Not so helpful in this sort of case, with little indication in lightning relative to the specific tornado times (or hail presence, which was already well-determined by radar). But great as situational awareness (like MESH) in making sure no dangerous cells are being missed.
Need to have trend plots, because it's too hard to figure out by querying flash count grids. The forecasters preferred a gridded plan view / map mode (not a line graph), and either a plot of (1) the flash rate derivative or, in the lightning jump sense, (2) the number of standard deviations (possibly fractional, e.g., 1.5) relative to the running mean. This could be implemented using the WDSSII k-means cell shape colored according to the above trend metrics. 30 min time lapse trend swath would also be helpful.
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.
Synthetic ABI brightness temperatures
Synthetic ABI brightness temperatures are being generated
at CIMSS and CIRA using output from the 00 UTC NSSL-WRF
4-km model simulations. Discussions have been held during
the past several days describing how infrared imagery can
be used to quickly evaluate the structural evolution of
the simulated thunderstorms and other cloud features as
well as to examine the overall accuracy of model
forecasts. Simulated IR imagery provides a powerful means
to quickly evaluate model output since various
characteristics such as cloud top height, water vapor
distribution, and thunderstorm coverage and intensity can
be inferred from a single image rather than having to look
at many different fields. As an example, the synthetic
imagery was used today to determine how quickly a
low-level stratus cloud deck present over the high plains
of NE Colorado and SE Wyoming would dissipate this
morning. Real GOES imagery indicated that the cloud cover
was not dissipating very quickly, which raised some
concerns that this would reduce surface warming and impede
the development of thunderstorms later in the day. A
quick examination of the synthetic 11.2 micron imagery,
however, quickly showed that this cloud cover would
dissipate by late in the morning. This provided greater
confidence that a risk for severe thunderstorms was
warranted over that region. The clouds did indeed
dissipate during the morning and several severe
thunderstorms, including one near the Denver airport,
developed during the afternoon.
-Jason Otkin
at CIMSS and CIRA using output from the 00 UTC NSSL-WRF
4-km model simulations. Discussions have been held during
the past several days describing how infrared imagery can
be used to quickly evaluate the structural evolution of
the simulated thunderstorms and other cloud features as
well as to examine the overall accuracy of model
forecasts. Simulated IR imagery provides a powerful means
to quickly evaluate model output since various
characteristics such as cloud top height, water vapor
distribution, and thunderstorm coverage and intensity can
be inferred from a single image rather than having to look
at many different fields. As an example, the synthetic
imagery was used today to determine how quickly a
low-level stratus cloud deck present over the high plains
of NE Colorado and SE Wyoming would dissipate this
morning. Real GOES imagery indicated that the cloud cover
was not dissipating very quickly, which raised some
concerns that this would reduce surface warming and impede
the development of thunderstorms later in the day. A
quick examination of the synthetic 11.2 micron imagery,
however, quickly showed that this cloud cover would
dissipate by late in the morning. This provided greater
confidence that a risk for severe thunderstorms was
warranted over that region. The clouds did indeed
dissipate during the morning and several severe
thunderstorms, including one near the Denver airport,
developed during the afternoon.
-Jason Otkin
Wednesday, May 26, 2010
SATCAST within Aviation Applications
The GOES-R Convective Initiation algorithm being developed by the University of Alabama in Huntsville within the GOES-R Algorithm Working Group Aviation Applications Team. Nowcasting convective initiation is very important to aviation interests for airport operations and airline planning. If there is a good indication that a storm will develop 30 minutes to 1 hour, the airlines can plan for a particular aircraft takeoff/landing route to close causing an airport to reduce capacity for take-offs and landings or shutdown airport operations. The airlines would be able to hold back some aircraft at other airports, preventing a backlog at a particular airport and cause airplane diversions which can be costly.
In addition, knowledge of thunderstorm growth can help airport operators plan for the potential of lightning strikes and clear the ramp preventing any possible injury/deaths from lightning strikes.
There were significant airmass thunderstorm development over Illinois, eastern TN, and over the Atlanta area today. Below is an example of SATCAST over the Atlanta region which is a major Delta and Airtran Airline hub.
SATCAST Nowcast valid 1702 UTC
Radar valid 1709 UTC
Radar valid 1903 UTC
Radar valid 2000 UTC
Below are examples over the Ohio valley. Notice the convection which developed over central Illinois and around the southern eastern KY area.
SATCAST Nowcast valid 1732 UTC
Radar valid 1733 UTC
Radar valid 1811 UTC
Radar valid 1830 UTCGOES-R Proxy products used in archive mode from 24 May 2010
The four forecasters split into two groups, one group focused on real-time storm development in western Oklahoma area while the other is looking at GOES-R proxy GLM lightning, convective initiation, overshooting-top, and enhanced-V signal from May 24, 2010 convective outbreak in Oklahoma area to take advantage of OKC LMA data. The figure below shows pseudo GLM (upper left), UW convective initiation (upper right), UW cloud top cooling (lower left), and visible lower right. This allowed forecasters to access GOES-R GLM proxy cloud-to-cloud lightning in conjunction with GOES imager based convective initiation/cloud-top cooling within AWIPS. Cloud-to-cloud lightning was shown to first occur at first indication of cloud-top cooling in this case.
Pseudo-GLM Archive Case: 24 May 2008
Looking backward at 1754, noticed CTC+CI, along with first lightning, simultaneously at 1702.
At this point, we hadn't noticed that GLM was slaved to satellite imagery updates, so GLM may have shown up prior to the CTC/CI.
No MRMS with this case (forecaster inquired about availability).
Might be helpful to have a suggested best practice for combining products in a display at outset of the case (ltng overlay w/satellite, ltng overlay with radar, etc). Careful to not slave GLM to satellite 15 min updates when doing overlay. Load GLM first.
18:16 - 50 dBZ core in cell in NE major county, 29-30kft
18:23 - "Blaine county going up quick" - based on <>
18:25 - CG activity dropped off in northern cell after initial flurry after initiation. IC modulating but holding steadeier than CG.
"Lightning data helpful for nowcasting - can but thunder in short term statements if there are just showers forecast. Don't have to rely on just CG data for thunder."
Blaine probably not going quite as quickly as initially thought.
18:30 - 64 dBZ 16kft in NW Garfield cell.
18:38 - Querying for mesocyclone signatures in radar on Major/Garfield storm. pulled up OK mesonet to look at low level inflow (very backed, just S of E)
18:34 - Blaine elevated core > 50 dBZ
CG data dropout at 18:20, restored by 19:00
Blaine remains of interest at 18:42- most vigorous updraft. Determined from radar. First GLM 18:43.
18:53 - Garfield storm has meso. 1855 - 60 dBZ to 20kft. Lightning picked up on southern storm a bit.
18:57 - storm top divergence on Garfield
19:01 - began to issue severe + tor in ctrl/western Garfield
18:30-18:35 - GLM showed increase right where core went up at same time.
19:05 - issuing svr on Blaine/Kingfisher storm
Screen real-estate an issue. Careful interrogation of radar means limited space for other data (e.g., GLM). Requires conscious context switch to notice any trends in lightning.
19:07 - noted that core growth in blaine was commensurate with jump in lightning activity
SPC mesoanalysis from the archives would be helpful to have on right screen during WES cases. (needs plugin though)
19:13 - "46 dBZ to 52kft on northern storm. huge overhang"
Just after 19Z spike to over 100, pulse to 125 at 1922-24 in northern storm.
19:27 - media report of tornado 2 W Lacey in Kingfisher county (southern storm).
19:39 - tornado lifted
19:45 - another reported tornado NE of Lacey
Lightning rate dropped from 80->40 in the 5 min before 1927 tornado.
19:56 - second tornado lifted
Northern storm noted to have eased off on lightning rate (to <>
20:07 - tornado report in the southern storm
EWP daily briefing and thermal couplets
24-hour thermal couplet detections and severe reports for 25 May 2010In today's EWP daily briefing, Wayne Feltz and I showed the 24-hour thermal couplet and severe storm reports maps from the UW-CIMSS website. The thermal couplet locations correlated well to locations of reported tornadoes, especially along a track through western KS (see above). The thermal couplet detection product has been brought in to the N-AWIPS system for the SPC and EFP as of yesterday, but we still have yet to be able to provide it within the EWP's AWIPS system. We attempted to make the changes today, but a power outage thwarted our efforts and has yet to be restored. We will be monitoring this throughout the evening and hope to have this working by tonight.
The plan for the day is to start with a pseudo-GLM archive case for two of the forecasters, while the other two monitor real-time weather in OK. We will adjust for interesting weather as is occurs...
Severe hail probability forecasts hail over central US
The severe hail probability product was examined this morning to determine what characteristics of what it showed following yesterday's widespread severe weather across most of the country. We noticed that the product performed well in forecasting the occurrence of severe hail over IA/IL/WI/AR earlier in the day, with probabilities exceeding 2% hours in advance of severe hail reported on the ground. Along the dryline in NM/TX/CO/KS toward the evening, the probabilities also were seen 1-2 hours in advance of severe hail reported on the ground, including one report of 3" along the CO/KS border. (see above images) The lead time slightly decreased along the dryline region where storm growth was much more explosive. This helps explain the decrease in lead time over this region as the product may not be able to detect these storms as far in advance.
SATCAST Identifies Severe Storms in Texas Yesterday
Yesterday, a line of convection developed over the Texas, New Mexico border. SPC issued a Severe Thunderstorm Watch at 3:05pm CDT over the region.
SPC Severe Thunderstorm Watch Issued 3:02pm CDT
SATCAST identified a line of growing clouds in New Mexico at 2:15pm CDT (1915 UTC). The convection grew into severe storms.
SATCAST output at 2:15pm CDT (1915 UTC)
The radar images from the region showing no convection within that region at 2:13pm CDT.
Radar image at 2:13pm CDT (1913 UTC)
Radar image at 2:51pm CDT (1951 UTC)
Radar image at 3:34pm CDT (2034 UTC)
SATCAST provided a lead-time of approximately 45 minutes before achieving a 35 dBZ radar reflectivity and the line of storms was identified for initiation approximately 45 minutes before the issue time of the SPC watch. This shows the utility of SATCAST in nowcasting possible severe convective weather and highlight areas of development up to an hour in advance.
Tuesday, May 25, 2010
Visible/IR blended imagery of enhanced V in AWIPS
The above image taken by the Amarillo, TX forecaster group shows multiple enhanced-V signatures on severe storms located in the TX panhandle at 0015 UTC in the visible. Blended on top in the IR brightness temperature image. These enhanced-V signatures, clearly observed on visible imagery near sunset, were not detected by the thermal couplet detection product because of the coarseness of the IR data. We can see the higher level cirrus above the main anvil, associated with the overshooting tops, possibly being the source of the warmer temperatures detected downstream of the overshooting top in the typical IR representation of an enhanced-V signature seen in case studies. Since the cirrus is associated with an overshooting top, which is likely penetrating into the lower stratosphere, the warmer stratospheric temperatures may be the cause of the warmer downstream temperatures.
A storm without lightning strikes?
During operations earlier this afternoon, a forecaster noted a storm in the northern Texas panhandle with an extensive 60 dBZ radar reflectivity core but without any lightning strikes reported by the National Lightning Detection Network (NLDN). The forecaster expected that such a mature this storm would be a lightning producer. And some storms are indeed prolific in-cloud lightning producers while rarely producing channels that strike ground. Many storms with high cloud flash ratios were observed during the STEPS field program (Lang et al. 2004).
The GOES-R Geostationary Lightning Mapper (GLM) would have been able to confirm lightning with this storm. The storm unfortunately was not over one of the ground-based Lightning Mapping Arrays that, like GLM, provide real-time total ground + cloud flash rates. Had it been, we would have examined flash rate tendencies associated with modulation in the storm's mixed phase updraft as a complement to radar indications of updraft processes that together provide situational awareness about the likelihood of severe weather threats.
Forecasters monitoring consistent overshoots during IOP
The Amarillo, TX forecaster group are monitoring consistent overshooting top detections above a storm slowly entering the southwest edge of their CWA (see image above)... They are preparing to issue warnings as soon as it enters. The consistency of the overshooting top detections are providing them with strong confidence that the storm is continuing to maintain its intense updraft and thus telling them that it is still severe. The magnitude of the overshooting tops, or difference between the temperature of the overshooting top relative to the cloud around it, has been slowly increasing from 4 K to above 9 K over the past few satellite scans. Note that these values may be diluted since the contours are smoothed, so the actual magnitudes are probably higher. Nonetheless, this may be saying that the updraft is strengthening. The forecasters are also noticing trends in the overshoot magnitude as severe weather occurs. There was a report of a tornado with this storm following the intensification, but that has yet to be verified. I mentioned that a total disappearance of the overshoot may indicate the occurrence of severe wind or hail at the surface as the updraft collapses.
The Pueblo, CO group have also been monitoring the overshooting top magnitudes, but for a different purpose. They have a cluster of storms and are using the overshoots to detect the regions of renewed intensification on satellite, since it is one large thick cirrus shield over the area and the radar signatures look somewhat similar.
UW-CIMSS real-time simulated/observed satellite verification
Scott Lindstrom and Justin Sieglaff from UW-CIMSS have developed a website for use in this year's GOES-R Proving Ground Spring Experiment to compare the simulated satellite imagery produced from the NSSL-WRF and the observed GOES-13 imagery in real-time. The website provides us with a quick comparison between the model's expected convective development and what is occurring in actuality. This helps us greatly in determining the model's performance on the fly for that day's 00Z run. This site has been and will continue to be used in forecaster briefings in the EFP and EWP to help us decide where convection will develop during the day.
http://cimss.ssec.wisc.edu/goes_r/proving-ground/nssl_abi/nssl_wrf_goes.html
http://cimss.ssec.wisc.edu/goes_r/proving-ground/nssl_abi/nssl_wrf_goes.html
Discussing SATCAST at EFP Briefing
After the active convective day on Monday May 24, SATCAST results were presented to at today's 3pm EFP briefing. Several examples were shown were SATCAST performed well and some weaknesses of the algorithm. Some of the dryline activity over TX was not nowcasted by the algorithm because of the strong growth rates of the convection over the GOES temporal resolution of 15 minutes. There was some good discussion about GOES-R 30 second rapid scan and whether that high temporal resolution is useful for the SATCAST algorithm.
EWP potential innovations
Today is not quite as exciting as yesterday, no watches all the way from Canada to Mexico. Some severe weather is expected over the TX panhandle as well as over WI. However, since WI is almost completely covered in cirrus and TX panhandle is relatively clear, we decided to monitor that area for the day in favor of the GOES-R products, localizing over Pueblo, CO and Amarillo, TX.
Archive cases are still building and would be difficult to go through at this point so we decided to run today's IOP like a normal WFO shift, where we will monitor the areas of interest and issue nowcasts for the first half until warnings are needed. This will allow for monitoring of the UWCI and CTC products in their intended roles. This is a wholly new idea for the EWP, as previously it had been focused primarily on warning operations only. The forecasters seem excited to do something similar to what they are expected to do during a normal shift. Depending on today's experience, we may have started a new trend for the EWP...
Archive cases are still building and would be difficult to go through at this point so we decided to run today's IOP like a normal WFO shift, where we will monitor the areas of interest and issue nowcasts for the first half until warnings are needed. This will allow for monitoring of the UWCI and CTC products in their intended roles. This is a wholly new idea for the EWP, as previously it had been focused primarily on warning operations only. The forecasters seem excited to do something similar to what they are expected to do during a normal shift. Depending on today's experience, we may have started a new trend for the EWP...
EWP daily briefing... debrief
During the first part of today's afternoon briefing for the EWP, we discussed the use of the UWCI and OTTC products from the 2130-2300 UTC time period. Below is the main points brought up in the discussion...
OVERALL
Products are provided as images within AWIPS. Image combine dims visible and makes hard to see. Would be nice to have something different... would be better to load a contoured fields... "I want to have as many things loaded on one screen as possible and I can turn them on and off... I had to use 3 panels to display the products and that's not good." (We did this for NAWIPS at SPC last year and is now on the todo list for AWIPS this year)
UWCI and CTC
CI vs CTC... bias towards one?... Liked CTC better... picked up about 15 minutes before radar and better discriminated areas of interest... showed more signal than CI.
Are you ok with more false alarms?... "As long as forecasters are trained, false alarms are not a problem. Even with CI itself... make it less stringent. I can tell if cirrus is over top of it. I know why you're doing it, but maybe you don't have to go as far."
"Is the anyway to have the CI continue to track a vertically developing cloud to see if the development continues?" (This is under development within WDSSII)
Forecaster mentioned that he used the UW-CIMSS CI phone application this morning... He had good impressions and would like to see that sort of display in AWIPS (similar to the "OVERALL" discussion)
OTTC
"I could make out that it was an OT before it could... about 30 minutes before. I guess this was because of the coarse grid, but by the time an OT was detected I already had a hook echo with a tornado on the ground."
We showed the 24-hour detections of overshoots and thermal couplets. The thermal couplets were much more confined to severe areas and the overshoots were much more widespread and matched with areas of CG activity, but both seemed to lag occurrence of severe weather.
OVERALL
Products are provided as images within AWIPS. Image combine dims visible and makes hard to see. Would be nice to have something different... would be better to load a contoured fields... "I want to have as many things loaded on one screen as possible and I can turn them on and off... I had to use 3 panels to display the products and that's not good." (We did this for NAWIPS at SPC last year and is now on the todo list for AWIPS this year)
UWCI and CTC
CI vs CTC... bias towards one?... Liked CTC better... picked up about 15 minutes before radar and better discriminated areas of interest... showed more signal than CI.
Are you ok with more false alarms?... "As long as forecasters are trained, false alarms are not a problem. Even with CI itself... make it less stringent. I can tell if cirrus is over top of it. I know why you're doing it, but maybe you don't have to go as far."
"Is the anyway to have the CI continue to track a vertically developing cloud to see if the development continues?" (This is under development within WDSSII)
Forecaster mentioned that he used the UW-CIMSS CI phone application this morning... He had good impressions and would like to see that sort of display in AWIPS (similar to the "OVERALL" discussion)
OTTC
"I could make out that it was an OT before it could... about 30 minutes before. I guess this was because of the coarse grid, but by the time an OT was detected I already had a hook echo with a tornado on the ground."
We showed the 24-hour detections of overshoots and thermal couplets. The thermal couplets were much more confined to severe areas and the overshoots were much more widespread and matched with areas of CG activity, but both seemed to lag occurrence of severe weather.
UWCI and OTTC first forecaster interactions
A new set of NWS WFO personnel from St. Louis, Des Moines, Buffalo, and New York were giving GOES-R training with respect to future satellite-based decision support for convective initiation, convective overshooting-tops, and thermal couplets (enhanced-V) detection. All the forecasters were very receptive to the training and asked excellent questions with regard to temporal latency and how products might help with situational awareness. After training was conducted each forecaster was given access to AWIPS workstation and allowed to set up environment as they would at their office. Four panel displays were constructed consisting of UWCI cloud top cooling rate (CTC)/convective initiation signal plotted over GOES imager visible imagery and vertically composited radar. Forecasters in general felt that the CTC rate provided more lead time and better quantitative magnitude based on verbal communication. In some instances no reflectivity was present on radar for up to 15 minutes after CTC indication, in other cases the product acted more as a diagnostic. Chris and I will look through evaluation forms (filled out after AWIPS interaction last night) and use those to help guide today's training. Here is a summary of yesterday's 24 hours (12 UTC - 12 UTC) UW CI/CTC compared to SPC reports and accumulated NLDN.
Initial evaluation of Overshooting-top/Thermal Couplets (OTTC) also occurred but forecasters spent most of their time first familiarizing themselves with UWCI products.
Initial evaluation of Overshooting-top/Thermal Couplets (OTTC) also occurred but forecasters spent most of their time first familiarizing themselves with UWCI products.
Monday, May 24, 2010
EWP examining potentially tornadic storms during IOP
The EWP is performing an informal IOP to familiarize the forecasters with the experimental data they will be using for the rest of the week following the afternoon training session. Today's focus for the first half of the evening is for the UWCI and OTTC products over N. TX into W. KS where a threat for tornadoes is expected into the late evening and overnight. Forecasters are examining the CTC product as well to determine the relative strength of the storm updrafts, which is made possible because the CTC product does not shut off until the storm has glaciated for two scans. Preliminary interactions with the forecasters have been promising regardless of some continued issues with the OTTC data. Forecasters have regularly been seeing lead times with the UWCI and CTC products of 15 minutes over radar, as well as their own subjective determinations of when convective initiation has occurred based on satellite or radar. They have also been finding that the CTC product has been providing them with some valuable information regarding the locations of the most vigorous updrafts along a line of storms. Wayne Feltz will be providing a more detailed update on his interactions with the forecasters.
UAH SATCAST_v2 Example Near New Orleans, LA
SATCAST-v2 Output from
1745 UTC GOES-13 Imagery
1745 UTC GOES-13 Imagery
SATCAST-v2 Output from 1815 UTC
GOES-13 Imagery
GOES-13 Imagery
The SATCAST_v2 algorithm forecasted the first convection of the day along the North Shore of Lake Pontchartrain with just under 30 minutes lead time for the cell in western St. Tammany Parish (see top-left image, above) and between 15-30 minutes for the cell along the St. Tammany Parish / Hancock County border (see top-left image and lower-right image, above). Because it was the first CI in the area for today, the 1744 UTC radar image, below, showed a clear scan across the entire region. However, these storms, and more, became apparent on radar only after a half hour or more elapsed. Within the next hour, the NWS office in New Orleans issued Special Weather Statements for this storm cluster, and they eventually had to issue the first Severe Thunderstorm Warning on the slow moving western cell around 2007 UTC.
Radar data valid at
1744 UTC.
Radar data valid at
1813 UTC.
Radar data valid at
1832 UTC.
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
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
SATCAST Convective Initiation Examples Over The Memphis Area
Today there is significant convection forming over the Memphis area. Since Memphis is an important airline hub for Delta and Fedex, knowledge of convective initiation is important for planning of airport operations.
Below are some images from the UAHuntsville SATCAST over the Memphis area at 1515 UTC. The red indicates the likely area of convective initiation.
Notice the red area in southwest Tennessee. The radar image below at 1516 UTC shows a complex of storms in west central Tennessee, but no convection in the area of the SATCAST nowcast.
Other radar images from 1526 UTC and 1531 UTC respectively are below.
It's important to note that some of the convection was missed over the TN/AR border due to the temporal difference between the images is 30 minutes due to a full disk scan (full disk scan on current GOES takes ~26 minutes to complete which occured at 1445 UTC and every 3 hours) and a housekeeping procedure at 1532 UTC. Because the convection was rapidly developing, 30 minutes was too long to provide sufficient lead time for some of the storms. Notice how quickly the storms grow over 30 minutes in the two 10.7 micron images below (the image times are 1445 UTC and 1515 UTC, respectively):
With GOES-R, CONUS scans will be available every 5 minutes which will be able to provide better lead-times for the convective initiation algorithm as opposed to the current 15-30 minute temporal resolution current available with GOES.
As the morning progressed, the aerial coverage of the convection increased, and SATCAST was able to depict this increase. Below are some examples of SATCAST depicting the increase at 1602UTC.
And the radar image from this region is below at time 1615 UTC:
It is also important to note that some of the smaller cells in the image above are not detected by the SATCAST algorithm. This is likely caused by the small spatial scale of the individual storms being less than the 4km spatial resolution of GOES in the Infrared region. GOES-R will provide an infrared spatial resolution of 2km which will allow for the smaller convective storms to be identified.
Week 2 begins... NSSL-WRF updates
It's Monday, which means week two of the Spring Experiment has officially begun. Bill Campbell from NWS HQ, Louis Grasso from CIRA, Wayne Mackenzie and John Walker from UAH, and Wayne Feltz and Jason Otkin from UW-CIMSS are here to participate within the Spring Experiment activities and interact with the forecasters this week. This morning was spent making some changes to the NSSL-WRF simulated satellite imagery. UW-CIMSS was having some issues with the 17Z forecast time period of their run, so their output now begins at 18 UTC. This did not affect the use of the data within the EFP much since most of the forecasts begin at 18 UTC. The times have successfully been extended out to the 03Z forecast period for all bands from UW-CIMSS as well. CIRA extended it's forecast times from 12-00Z to 12-06Z for bands 8 and 13 over the weekend. This change has been implemented in our ingest scripts and the images are now available within any SPC and HWT N-AWIPS system.
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