Az Shear Possibilities

I’ve seen some great promise from the low level az shear this week so far. One thing that I do not like about the default product is that it has a lot of noise/extra info in it that tends to clutter up your screen. An idea that I had was to filter more of the noise by making a large portion of the scale transparent. Take a glance at the velocity field and see how it matches up with the AZ shear extremes.

Shown here is a comparison of the default vs the “enhanced” low level az shear.

Another advantage I could see with only displaying the “extremes” would be the ability to include velocity data underneath the image. This can be especially useful since the MRMS data is feeding the AZ Shear. Why? Well the velocity couplet you are examining is likely to progress a bit “faster” using the baseline radar data rather than MRMS, so they likely will be right next to each other.

Az Shear overlay on Velocity Data

Other thoughts I have had going this route is possibly changing the “red” side of the color scale to something other than red so that it doesn’t match the color scale used by velocity data on radar. I did like a “yellow” scale as it did not largely conflict with the color scales expressed by the velocity data.

An attempt at a “yellow extremes” color table.

As a whole I think this product has some great potential at drawing your attention to portions of the storm very quickly.

South Beach

Low-biased MESH

At 336pm CDT, a supercell storm near Electra, TX produced golf ball sized hail despite MRMS MESH showing sub-severe hail (~0.85″). Despite the low MESH, ProbSevere hail was progged at 75%. KFDR data had 50+ dBZ above 34K feet MSL and the storm was highly tilted downshear (a known limitation of MESH – underestimates in this case). This storm highlights the need to couple MESH/ProbSevere products with a thorough analysis of the base radar data and a fundamental understanding of strengths and limitations of supplementary datasets.

–Stanley Cupp

Underwhelming ProbHail

ProbHail on the storm in southwest MO seemed to be too low based on other derived parameters (MESH/Hail Index) and storm structure. ProbHail was consistently 70-75%. It was explained that the hail cape (~750 J/kg), the EBShear (47kt) and lightning (29 flash/min) were relatively lower than one would expect given the environment. Justin showed the parameter space for each of the ingredients and how they were weighting down the overall ProbHail due to the ratios being <1.

— SCoulomb

SJT Mesoscale Discussion

There is a warm front draped across the northern portion of the CWA with widespred cumulus developing along the front and broken skies in the warm sector. GOES-16 Day Cloud Convection RGB and Day Cloud Phase RGB show that a few of these storms have already glaciated indicating the convective initiation is underway. (Below)Laps All Sky retrievals show a relatively sharp instability gradient along warm front where our convection initiated. Storm motion is likely to be parallel to the front, so convection that does will likely be relatively long lived. (Below)Laps All Sky LI further indicates that the airmass is relatively unstable and there will be little convective inhibition at least in the midlevels. (Below)All Sky TPW indicates a relative moist airmass across the CWA with PWs above 1″ for most of the CWA. This matches the 12z sounding from MAF relatively well, and is well above the 90% threshold of the sounding climatology for that location and date. It’s interesting that the mid-level moisture (bottom left) is higher than the low level moisture (bottom right). Not quite sure what to make of that at this point. (Below)Finally, MRMS RALA indeed shows that showers and storms have developed along the front. When animated (not shown), you can see that the storms are tracking along the front, heightening my concern for flooding. 

Sandor Clegane

Miscellaneous musings from ALY

Had an interesting day working with convection in Albany’s CWA today.  Several storms grew big enough to make severe hail, strong winds and show nice organized rotation..also a bow echo looking storm.  In general the 3D Var and MRMS products proved useful for detecting hail concerns and also evaluating whether or not updrafts were strengthening or weakening…how high they were and whether or not there was good updraft helicity/vorticity.  Also the azimuthal shear product from MRMS was useful/interesting.  The nearcast thetha e product had its scale and units reversed since yesterday which caused some initial confusion but did seem to depict the more unstable regions well…though instability was fairly marginal.

Some product limitations we ran into:  With all the new fancy products we had, there really wasn’t anything to aid with max wind gusts.  With the bow echo storm the 3d var fields were barely perturbed and did not at all seem representative of the probable wind speeds (images below show reflectivity and 3d var quad at same time with 1km (lowest available) winds…higher levels didn’t show much either)…old school use of radar velocities worked much better.

Some other products that would really be nice to have would be a 3-d or cross section way to look at updraft and downdraft strength, the horizontal plots of this could be overlayed at 1 km spacing in 3 d-var and was useful to watch through the life cycle of the storms but was very clunky to step through and hard to mentally visualize. In a 3d view this could be a very powerful way for forecasters to monitor and diagnose storm structure.  Another thing we ran into today were training storms and flash flood concerns…dual pol was handy for this among other things but wonder about what applications of the fancy new products there might be to hydro concerns.

AWIPS 2/Warngen/CAVE issues continued again today with warnings that wouldn’t go out, multiple Cave crashes, lots of random error messages and slow downs.  This system is not at all ready for operational use as they slowed/prevented warning issuances and having Cave crash mid warning ops when all the work station is running are 2 Caves not at all confidence inspiring when you think about everything else AWIPS in WFOs runs and does in addition.  Also found an interesting bug with the map background in the quad panels where they don’t always stay linked and you can unpredictably end up with map scales and alignments in different sections of the quads.

Another SVR in eastern NY

Another storm is affecting eastern Saratoga County and southern Washington County, NY (prompting a severe thunderstorm warning).  3DVAR storm-top divergence has been a pretty solid predictor with other storms in the region today, and this storm was no exception.  However, this was the first storm to show more than marginal updraft helicity, maxing out at 117 m/s^2 at 2045 UTC.

3DVAR Reflectivity, Updraft Composite, Updraft Helicity, and 10km Divergence valid 2012-05-16 2050 UTC
3DVAR Reflectivity, Updraft Composite, Updraft Helicity, and 10km Divergence valid 2012-05-16 2050 UTC

About 15 minutes later, MRMS MESH reached 1.25″ with a 62% POSH; that has since increased to 72% POSH and 1.5″ MESH.

BTV: 3DVAR/MRMS usefulness

A short line of storms developed rapidly over Essex County.  The MRMS data (lower right pane) indicated a MESH of nearly 2 inches!  At the same time, the 3DVAR vertical velocity data (upper right pane) was 14 m/s for the same cell.  Using this data against already high reflectivity (upper left) increased confidence for a warning, especially given the environment.  Unfortunately, the 1KM wind field (lower left) gave a mixed signal at the same time frame, which was possibly an effect of the terrain.

Monitoring More ALY-area Storms

Two more storms in extreme northern Saratoga County, NY are being monitored for warnings (update: an SVR was just issued for the northern storm).  3DVAR has shown the same signals as the Herkimer County storm with strong storm-top divergence:

3DVAR 10km Divergence valid 2012-05-16 1930 UTC
3DVAR 10km Divergence valid 2012-05-16 1930 UTC
3DVAR 10km Divergence valid 2012-05-16 1935 UTC
3DVAR 10km Divergence valid 2012-05-16 1935 UTC

MESH was peaking just under 1″ with near-50% POSH.  (Update: it has increased above 1″ and POSH is above 50% now, prompting the warning.)

The UW CTC was also strongly negative in eastern Hamilton County at 1925 UTC, indicating a CTC of less than -30 C/15 min, so northern Warren County will need to be monitored.

Visible Satellite, UW CTC, and UAH CI valid 2012-05-16
Visible Satellite, UW CTC, and UAH CI valid 2012-05-16 1925 UTC

ALY: First Warning of the Day

A three-body scatter spike and strong indications in the dual-pol data have led the decision to a severe thunderstorm warning for hail in southern Herkimer County, NY.

KENX Reflectivity, Velocity, ZDR, and CC valid 2012-05-16 1920 UTC
KENX 0.5-degree Reflectivity, Velocity, ZDR, and CC valid 2012-05-16 1920 UTC

Neither MRMS nor 3DVAR are as impressed with the storm.  Updraft intensity fields in the 3DVAR are rather weak, but there were indications of strong 10km (storm-top) divergence (greater than 9.5 s^-1) starting at 1915 UTC.

3DVAR Analysis Reflectivity Composite, Updraft Composite Maximum, Max Updraft Track, and 10km Divergence valid 2012-05-16 1915 UTC
3DVAR Analysis Reflectivity Composite, Updraft Composite Maximum, Max Updraft Track, and 10km Divergence valid 2012-05-16 1915 UTC

MRMS MESH has peaked under 1″ and had just a 38% POSH.

MRMS MESH & POSH valid 2012-05-16 1924 UTC
MRMS MESH & POSH valid 2012-05-16 1924 UTC