Rapid City's Mesoanalysis/Analysis/Warning Operations

Noticing a gradient in instability within the UNR forecast area. Will put image in showing this.  It is comparable to the NAM12 gradient in instability.  Did notice that the Layer precipitable H20 also has a gradient in moisture spreading into the eastern half of the forecaster area but especially to the east over Aberdeen.

 Would expect additional increase in intensity as storms that area already developing across the northeastern sector of Wyoming. Am noticing that the highest Prob products (severe, hail, and wind) are coinciding with the strongest updrafts within the storms located over Billings area (2102Z).  Did look at a few NUCAPEs soundings which show a pronounced dry layer from 700mb-sfc. In a NUCAPEs sounding, I do like the readout but would like to see where the cloud layer is, instability, PWATs, etc.; displayed on that readout so that when we move mouse over individual points we can instantly see that data (rather than having to click on each individual point.  Will try to insert an image to better describe.

The GOES R GLM data is challenging to understand given how far northwest in the CONUS this is.  Seeing a lot of parallax. So, not sure its too useful for this office until GOES-S becomes operational.  Loaded ENTLN and NLDN into a procedure to compare with the GLM data and garner a better picture of lightning. 

The UAH CI product had lapses in time or late between 2032-2100Z data. It was affecting my procedures that had both satellite and UAH CI data.

Noticed that core of storm in western portion of UNR CWA had a distinct reflectivity gradient while Prob hail was decreasing. So, it could be that the hail was descending from the core. Given the dry air layer in the environment, it may be more of a microburst than hail impact with this storm. Went ahead and issued a severe for 60 MPH and nickel sized hail. Prob Severe, prob hail, and prob wind then increased on the next couple of scans attendant with the storms moving over the gradient in instability at 2206Z.

Prob Hail was actually higher than Prob Wind at times which was a little surprising given the prevailing environment but may be because the storms were a little more elevated.  As additional storms moved into the "gradient of highest CAPE" in UNRs northern area the Prob Severe and Prob Hail increased.  I do like the cursor readouts with the Prob Severe/hail that include CAPE within the hail growth zone and MESH.

Some other notes: I think it would be helpful to have Near Storm Environment Cursor Readout to compare what we are seeing in NUCAPs, GOES- All-Sky LAP products for hail and wind environments.

Did notice that the warnings we are issuing are in all caps and don't have the tags on them (tornado/hail/wind) at the bottom. Perhaps to make it more high fidelity, it may be useful to have that as well.

The area was loud while other HWT participants (another project) came into our area and were talking for an hour or two about everything but the project.

V/R
Supercell

Editing NUCAPS Sounding

19Z NUCAPS sounding available for far SE Montana but no 22Z available around peak heating. If wanting to see how much the atmosphere has destabilized in the three hour window, I edited the sounding to match surface obs.

19Z NUCAPS sounding.

Looking at nearby surface obs around 22Z, which were lacking, and the SPC surface mesoanalysis, I edited the 19Z in the lowest levels based on nearby obs 79 temp and 46 dewpoint.

Edited 19Z NUCAPS sounding to match 22Z

While not dramatic, there was a noticeable increase in CAPE values during the 19Z to 22Z window. This was also noted on the AllSkyLAP Layer CAPE loop over the same time window.

As of 22Z Monday storm initiation had not occurred over far SE Montana. but earlier convection north and west was working into the region as vort max continues to trek across Montana. To be seen is new initiation develops over the region.

- Jack Swigert

ProbHail Overestimating Severe Hail in Montana.

MRMS Composite Reflectivity over southeast Montana on Monday afternoon 2022 to 2136Z with ProbHail overlaid. Convection firing off near the Billings area with individual cells displaying high ProbHail values of 50 to 80 percent in the initial and mature phase of development. This was due to MESH values of 1" to 1.7". Issued 3 warnings for hail size of 1" but storm reports of only 0.25" to 0.88" were received before the storms weakened as they worked east of the Billings area.

- Jack Swigert

HWT 2018: Week 2, day 1: BYZ & UNR

As we get the ball rolling on week 2, the weather takes us further northwest -- Billings, MT and Rapid City, SD.  The forecasters are currently setting up and getting familiar with the variety of GOES and JPSS products available to them. 

Initial outlook for today is not very exciting for those in search of severe weather.

There is a decent chance for severe weather associated with and ahead of the short wave moving through Montana and across South Dakota later today.  Unfortunately, much of this may occur at or after we end operations for the day.

Currently, small storms with some lightning are ongoing in central and southern Montana and a small field of Cu is developing in western South Dakota.

30-min of GOES-16 VIS (ch. 2, 5-min update) and GLM Total Energy (5 min-summation, updating every min).

For day 1, however, the goals for the forecasters are primarily to get acquainted with the variety of products available and begin building AWIPSII procedures they will be able to incorporate throughout the week. Hopefully, we will see a wider variety of severe weather as the week continues.

-Kristin Calhoun
Week 2 Coordinator
GLM Science Lead

Week 1 Wrap Up

The first week of the 2018 HWT Satellite Proving Ground Experiment is wrapping up today. It has been a great week with active weather and 5 forecasters providing some valuable feedback for the week on a host of products. Monday will begin week 2 of the experiment.

Michael

Tornadic storm near Des Moines

As a surface low pressure system tracked northeast through central Iowa last night, one storm near the center of the low spawned at least one tornado southeast of Des Moines, IA. The first report came at 00:38 UTC, about 13 minutes after the first tornado warning. The ProbTor product from ProbSevere version2 showed elevated probability of tornado values (≥ 20%) as early as 23:48 UTC.

Figure 1: ProbTornado contours, MRMS MergedReflectivityComposite, and NWS severe weather warnings.

From the time series below, we see that increased rotation (0-2km MRMS AzShear; solid orange line) and increased total lightning density (solid green line) helped jump the probability of tornado from single digits to 40% at 00:00 UTC, and again from 20% to 50% between 00:26 and 00:38 UTC. The effective bulk shear and 0-1 km storm-relative helicity were clearly adequate, but not outrageous (~40 kts and ~150 m2/s2, respectively).

Figure 2: Time series of ProbTor and predictor values. The bottom axes contain NWS warning durations and LSRs.

One thing forecasters should look for when using ProbTor is when a storm's probability of tornado "sticks out" amongst the values of neighboring storms. This storm is a good example of that, where neighboring storms in a 4-county radius had probabilities in the single digits.

Forecasters should also be aware that the probability will fluctuate more with ProbTor than the probability of severe. This storm exhibited some fluctuation, whereby probabilities rose from 7% to 43%, dipped to 20%, and rose again to 55% during the tornado(es). ProbSevere developers are working on incorporating a visual time series function in AWIPS2 for ProbSevere storm objects (similar to Figure 2), so that forecasters can quickly see the history of a storm, which may help in warning decision making.

Lastly, there is no "magic" threshold of ProbTor for when tornadogenesis is imminent. Very potent environments characterized by SPC's "moderate" or "high" risk for tornado might see ProbTor values in the 70-90% range for tornadic storms, whereas for a more common tornadic environment like this, 20-50% can be expected for tornadic storms. In environments where tornadoes are not expected, ProbTor values of even 10% might be significant.

Users of the ProbTor product should keep these points in mind, but ultimately, forecasters should become more comfortable with the product as they gain experience with it in different regimes.

Please see our training module for more details on ProbHail, ProbWind, and ProbTor, and this fact sheet regarding the differences between ProbSevere version1 and version2.

GLM 1-min vs 5-min Accumulation

For most of the week, the products from GLM were 1-minute updating every 1-minute. For this user, it was difficult to identify relevant trends in the fields (rapid increases or decreases), or to connect lightning cores with their appropriate storms as seen in radar imagery. Today, the products were converted to 5-minute accumulation (updating every 1-minute) about midway through the shift, allowing for a comparison between the two methods. See below. The 5-min accumulation updating every 1-minute, in my opinion, allows for much easier identification of significant trends, as well as tracking of lightning cores and relating lightning features to radar imagery.

The animation below includes 1-min visible imagery with 1-min GLM Flash Extent Density overlaid. The loop begins with the 1-min product, and transitions to the 5-min accumulation product updating every 1-minute.

The loop below includes 5-min visible imagery with the 1-min product overlaid, transitioning to the 5-min product midway through.

- Bucky

Give me Flash Area or give me death - P Henry

A good IDSS example.

A single product such as Flash Extent Density provides limited information about a flash and potentially storm behavior. Pairing FED with Flash Area as in this example helps more easily diagnose the long flash through the stratiform region of this storm over northern IA. The higher flash rates associated with the smaller flash sizes along the leading edge of the northward moving complex are more easily explained with the companion product. As the flash extended north into MN and another CWA, this information could be used to enhance DSS since the main convective line was still 50-60 mi away. ENI and other commercial lightning networks would not have alerted to the threat of lightning overhead at such a great distance. An event organizer or EM looking at static radar also may not be aware of the increased threat of lightning well ahead of the main storm band. SCoulomb

ProbSevere running hot in Iowa

ProbSevere has been running hot, with probability of hail and probability of wind, pulsing into the 30-50% and 60-80%, respectively for many storms across the DMX WFO.  Thus far no severe reports have been received.  In discussing the environment with the DMX team, we are wondering if the shear is too high for the amount of instability, which is shearing the tops off developing storms, preventing storm organization.  The tops being sheared off can be seen in 1 minute GOES-16 visible imagery (not shown).  One silver lining would be ProbSevere Version 2 probabilities are 10-40% lower than the ProbSevere Version 1--illustrating the better calibration of probabilities in ProbSevere Version 2 relative to Version 1 (although still too high for the small sample size of a few hours this afternoon in the DMX region).

-J. Sieglaff

CI is Trying It's Best

Here is a 2-hour VIS loop of 1-minute data.  Overlayed is CI Probabilities.  The values seem to bounce around a lot, but are overall pretty low.  Even in locations where they are higher (green and yellow) not much convection develops from the cumulus.  The cirrus contamination diminished the potential.  Overall, the product needs more work to improve forecaster confidence.

-Kevin