Tuesday, July 22, 2014

ProbSevere MRMS fields vs. Single-source radar fields

NOAA/CIMSS ProbSevere display with kapx 0.5-degree Base Reflectivity, 1744 UTC on 22 July
Note the radar object above, enclosed in purple, from the MRMS (Multi-radar, Multi-sensor) fields, differs from the 0.5 Base Reflectivity field from the Gaylord, MI radar displayed.  This is to be expected because the MRMS is composite reflectivity from a variety of radars (in the case above, likely Gaylord, Marquette (MI) and Green Bay (WI)).  Do not expect a field from a single radar to overlap the MRMS fields.

(Scott Lindstrom, Ben Herzog)

Thursday, July 10, 2014

Severe Storms in Northwestern Arkansas

As the CIMSS/MKX GOES-R Proving Ground shift wound down Tuesday afternoon, severe thunderstorms rapidly developed over northwestern Arkansas.  This region was supportive for strong to severe thunderstorms with MUCAPE between 2500 and 3000 J/kg and effective bulk shear 20-30 kts.  Figure 1 below shows the NOAA/CIMSS ProbSevere Model overlaid on MRMS composite reflectivity.  Of note is the rapid increase in the ProbSevere values over the course of 6 minutes between 2032 UTC and 2038 UTC 08 July 2014.  At 2032 UTC the ProbSevere value was 8%, then at 2034 UTC the ProbSevere value jumped to 56%.  This jump was attributed to more intense satellite growth rates (the normalized vertical growth rate went from 1.4%/min (strong) to 2.6%min (quite strong) and the glaciation rate increased from 0.02/min (weak) to 0.06/min (strong)) as well as a jump in the MRMS MESH associated with this storm 0.35" to 0.52".  Another four minutes later at 2038 UTC the probability jumped again to 95% as the MRMS MESH approached 1.00".

Figure 1.  NOAA/CIMSS ProbSevere Model and MRMS Composite Reflectivity over northwestern Arkansas during late afternoon of July 8 2014.

This example illustrates the increase in lead-time to severe hazards as well as severe thunderstorm warning issuance that is possible by quantitatively using satellite growth trends with environmental information and radar observations of a storm's precipitation core.  In this example, the initial severe thunderstorm warning was issued at 2059 UTC--20 to 25 minutes after the significant jumps in the NOAA/CIMSS ProbSevere output.   More storms continued to develop further west during late Tuesday afternoon, most of which became severe thunderstorm warned after reaching high levels of NOAA/CIMSS ProbSevere values.  Only one severe report was received with these thunderstorms, but one wonders if this is more related to the population of very rural northwestern Arkansas--with much of this region covered by state and national parks (Figure 2).

Figure 2.  Google maps showing the one severe hail report received with these storms (green 'H').  The very rural nature to the area inferred by this map makes one wonder if more severe weather occurred than was actually reported.

-Justin Sieglaff, UW/CIMSS
-Steve Hentz, NWS MKX

Tuesday, July 8, 2014

Low Topped Wisconsin Storms

The synoptic setting for Wisconsin July 7th 2014 featured a small shortwave in a mid level trough over the upper Great Lakes.  MUCAPE values ranged from 300 to 800 j/kg with 0-6 km shear around 25 to 30 kts.  Scattered thunderstorms developed by noon.  SCAN max hail values were from 0.50 inch to 0.75 inch.  The CIMSS probabilities over severe were mainly in the single digit to around 25%, but many storms did have strong vertical and strong glaciation rates.  One storm did approach severe criteria. Using FSI with the Donovan technique a narrow core of 50dbz did just reach severe criteria.  The CIMSS Probability of severe was low at 49% , with the MESH value around 0.50 inch,   giving confidence that the storm was not severe.

-Steve Hentz

Wednesday, June 11, 2014

ProbSevere over the Mid-Atlantic and Southeast, 11 June 2014

We lost the NOAA/CIMSS ProbSevere feed at the National Weather Sevice (NWS) Milwaukee/Sullivan, Wisconsin (MKX) at 1742 UTC 11 June 2014. This was due to a communications failure at the National Weather Service Central Region Headquarters. So, we could not use and save the AWIPS II radar imagery with the CIMSS ProbSevere product.

However, we were able to save the images below from the ProbSevere website. These images were of convection in the Mid-Atlantic and Southeast U.S. from the early afternoon hours on 11 June 2014. We could not zoom in on the individual storms to get actual values from the ProbSevere product, so I'll just give some general trends on how it performed. Scattered convection developed across the region in a moist, unstable environment with 1000 to 2000 J/kg of MLCAPE, and 0 to 6 km shear of 20 to 30 knots. 

Convection developed fairly rapidly, and the ProbSevere values increased quickly as well. They seemed to show the rapid intensification of these storms well. Several Severe Thunderstorm Warnings were issued (yellow polygons) after the ProbSevere values increased rapidly. The ProbSevere product seemed to show some lead time to the issuance of the Severe Thunderstorm Warning products.

I have used the ProbSevere product in a couple of convective events in 2014 across the MKX forecast area. It was a useful situational awareness tool when convection first developed, until the anvils overspread the area. After then, it seemed to show more false alarms.

I would like to see an option to show the probability of tornadoes, severe hail, severe wind and flash flooding, if possible. Anything to help with situational awareness with flash flooding situations would be very helpful. It would also be good to try and keep the readout from the ProbSevere product from getting too cluttered with information. The color scale may need to be modified to one that has more colors at the higher end of the ProbSevere spectrum. This would help with seeing how high the value actually is.

This was a helpful learning experience, and look forward to more in the future!

Thanks,

JJW, Forecaster
NWS Milwaukee/Sullivan, WI

Contour colors: Blue - 1-9%; Cyan - 10-29%; Green - 30-49%; Orange -  50-69%; Red - 70-89%; Pink - 90-100%.
Polygons: Yellow - severe thunderstorm warning; Red - tornado warning; Purple - special marine warning.


Friday, June 6, 2014

Week 4 Summary and Feedback

Below is feedback from our final, week 4 weekly debrief session, along with a photo of the week 4 participants.

This marks the conclusion of the GOES-R portion of the 2014 HWT Spring Experiment!


- Bill Line, SPC/HWT Satellite Liaison



Simulated Satellite Imagery:
- It’s great to use the imagery to evaluate model performance.
- Had issues with burning off low stratus too early, leading to errors with heating during the day and errors of convection timing
- Do you see simulated model imagery being useful in forecast environment; would you like to see this data with other high res models?
    o All say yes, it is useful and would like to see it with other models (hrrr, etc)
    o Higher res models might pick up more discrete features things
 - Easy ways to pick up on errors in the model

Nearcast
- I used it mainly for ted and pw, it almost shows this better then anything I have in my office
- Nice to have in awips to overlay other things
- Helpful to show where boundaries will move, areas that are moistening
- Best as a precursor, ~3 hours prior to ci mostly
- I like the fact that you could really key in on boundaries, and I saw convection go there.
- Even subtle gradients up in high plains, small increases in ted, see showers pop up
- In Raleigh, having a tool that may easily show boundaries, esp in spring and summer, it could help
- I see more utility in theta-e and ted than in the PW field
- Calibration issue, we are used to looking at CAPE and LI. What does the ted values mean? Is there a way to do this?
- Its real-world information, which is good
- Overlayed forcing parameters on it.

Ci
- Didn’t increase my confidence as much as I had hoped
- One cell I tracked for a while in Huntsville area, had pretty high value, that did go up and eventually became strong
- Get rid of lower values

Probsevere
- This is especially useful for more slowly developing convection. Storms that look the same may have different probs, pointing out which storms are actually more threatening,
- Not as useful when convection is rapidly developing. The 1-2 scan lag hurts
- Good as a confirmation tool even for mature convection
- Good for slowly developing storms, detects hail well, poor with wind, not sure with tors. Prob severe hail may be better name. Rapidly growing convection, it wasn’t as useful with lag (1 volume scan), which hurt.
- Broadcaster – I really enjoyed this product. I am doing a lot during a day, especially severe day, it pinpointed where I should look. Same with CI
- Right now, as a regional SA tool, storms coming in from neighboring CWA, would be good to watch. Also for updating warnings.
- Column velocity to determine wind threat,
- Seems like product that has room to do some interesting things.
- with prob severe/hail/wind/tor, have a 4 panel, with total severe and 3 threats. Different parameter underlaid each

Overshooting Tops
- Broadcaster – really useful for me, in busy environment. I can speak for every broadcaster, we’d all love to have this product.
- More utility at night than during the day
- Helpful to CWSU cause I'm looking at a much larger area

Tracking tool
- This trend information is beneficial to have.
- Probably best for warning coordinator, or for research purposes. It is high maintenance, takes a lot of work to use

Lightning
- Broadcaster – lightning is especially useful for me, the chopper folks are constantly asking me where there is lightning to decide whether it is safe for them or not
- Most useful for rapidly developing convection
- Any time a jump occurred on a storm, the dBz’s would spike soon after
- I think it is everybody’s favorite thing, the lightning
- Most helpful for a warning operator, everything else was more SA.
     o Mostly because we had information every minute.
     o Getting additional info while we are waiting for next volume scan
- It impacted my warning decision making process.
- Especially useful in rapidly developing convection
- Broadcaster – lightning is very important even if it isn’t severe
- I wish I had more time to look at it.
- Training for lightning is not that good, to understand more why/how this is working, would be helpful. Why in certain environments and situations would it not work so well. But why better in others
   o Explain what is going in and why it is working

Broadcaster – from this perspective, most of the products demonstrated make it easier for him to do his job, because he can easily spot where a new storm is coming up in busy situations, where lightning is increasing. It helps make things easier for everyone at station.

CWSU – CI and OTD would be most useful for me, covering a broad forecast area. OTD quickly shows me where the strongest updrafts are, and ci highlights where convection is initiating or most likely to initiate in the near future. Also, lightning data is valuable for me.

General – be cautious of data overload. Products have to quickly prove their worth and utility in operations. Some products might be more useful for a warning coordinator, while lightning and maybe prob severe could be helpful for radar operator

Overall
- 1pm briefings from EFP, is there a reason for us to be in on that. A lot of it was not important
- Even from the briefings, I had no idea what was going on. It seemed more like a debrief for themselves. It had no application to us, it was geared to the efp
- I could have better spent my time making myself aware of the meeting.
- Schedule our debriefing during that, and maybe have it earlier (noon)?
- Since a lot is pre convective environment, we should come in at 9 or 10 to start.
- To be able to look at these products with other convective modes would be useful too.
- Broadcaster – recommend others to get with local wfo and get a couple hours in front of awips. Simuawips helped quite a bit.
     o This is most fascinating week of science I've had in a while.
     o Very much against working with just broadcasters in the hwt, found it very beneficial to be here with nws mets.
- All forecasters gained, learned from each others unique perspectives. Against segregated experiments.

Thursday, June 5, 2014

Daily Summary: Week 4, Day 4 (5 June 2014)



Today, we operated in 3 county warning areas:

Team 1 (Fowle & Anderson)
Boulder, CO

Team 2 (Pelczynski & Satterfield)
Pueblo, CO
Huntsville, AL

Given the potential for cirrus-free skies and a lightning mapping array, we elected to operate in the High Plains where another upslope day was expected.  In particular, we chose the Pueblo and Boulder CWAs.  However, it became clear that the Pueblo CWA would wait to convect until later.  Given our time constraints (ended at 7 pm to start surveys), we decided to operate in the Huntsville CWA, where a very fast-moving MCS would move into a lightning mapping array.  Most of our experimental products were used, including the OUN WRF.  Several severe storms formed in both active CWAs, with multiple lightning jumps observed in both.

-G. Garfield
Week 4 Coordinator

Blog 13 June 5 HSV Area

Wind Damage in Sylvania (in Dekalb Cty) AL. OT Top detection correlated very well with this. 2245 OT Top detected damage report at 2311Z 5 June.1 sigma light jump at 2225Z as well!



2320Z D Satterfield

ProbSevere and S. Colorado Severe

The ProbSevere model captured the development of severe weather in southern Colorado nicely during the evening of June 5. With one cell in particular, the first probability over 50% provided 20 min lead time to the first reported severe weather (1″ hail).

The algorithm started tracking the cell at 2136 UTC giving it an initial probability of 9% (to the first severe, Fig 1). At 2210 UTC, the algorithm had its first probability over 50% with a prob of 65%, indicating the cell was more likely than not to produce severe weather (Fig 2). The first severe weather of 1″ hail was reported with this storm 20 minutes later at 2230 UTC (Fig 3). The probability had maxed out at 85% at 2216 UTC.





- Bill Line, SPC/HWT Satellite Liaison

Blog 12 June 5 HSV Area Cherokee County AL

In the last post I mentioned the prob severe as not as helpful today. We now have a cell in Cherokee county ahead of the MCS that has an OT Top detect and a 4 sigma jump in lightning. Prob Severe now at 80% with strong flash density. HUN has warned and with all of these present expect severe reports. In this case it was warned because of history of these storms but all of this increases confidence in the warning and that this storm is still likely getting stronger.. was not as impressive 30 mins ago.

DSatterfield 2255Z


ProbSevere Improvements

Couple quick thoughts on ProbSevere improvement – based on threats:

Wind:

T/TD depressions

Subcloud/Low Level RH

0-3KM Shear

DCAPE

Vertically integrated “core dump” e.g. track descending Z core

Hail:

Areal extent of negative ZDR cores on 0.5 degrees (difficult)

H7-H5 Lapse Rates

CAPE in Hail Growth Zone

500MB Temps

Tornadoes:

0-1km Bulk Shear

0-1 SRH

MLLCL



Fowle