Author: Brandon Smith

May 2, 2019 All Sky Total PW vs Merged Total TPW

Posted in Live Blogs, Mesoscale Discussions on by Brandon Smith.

Figure A

All sky continues to handle total PW better than CIRA Merged Total PW looking at the bottom two frames. Notice the westward expansion of better moisture in the All Sky which matches up with surface obs compared to much lower values further west on Merged Total PW.

Figure B

Looking at the lower left panel for CAPE in the All Sky product we see a well defined instability gradient in southern FWS area which has our interest for higher probability of severe weather. Storms across central and northern parts of Dallas/Fort Worth area will be elevated, however storms that develop in southern part of the CWA could become surface based along the instability gradient.  -Jake Johnson

Figure C

RAP13 0-3km CAPE is favorable for surface based storms in far southern FWS CWA.

Today’s Experimental Operations – May 2, 2019

Posted in Live Blogs, News, Operations Status Message, Outlooks on by Brandon Smith.

Today’s operations will be focused over the SJT (San Angelo), FWD (Dallas/Fort Worth), and EWX (Austin/San Antonio) county warning areas.  Focus is once again ahead of an outflow boundary left over from overnight storms.  To keep with the theme this week, storms are again on-going at the start of the operations period with a severe thunderstorm watch in place over a portion of the operations area.  Supercells will be possible today but the scenario will be messy with storm interactions and mergers likely.   The main threats today are hail and high winds but a few tornadoes are possible.

Tags: None

All-Sky products and boundaries

Posted in Live Blogs on by Brandon Smith.

As many have already mentioned, the new All-Sky LAP layered PW and CAPE products are very useful tools for mesoanalysis and quick identification of key meteorological gradients (I bet my grandmother could ID the dryline below…). Earlier today, these products seemed to pick up on the outflow boundary that stretched from SE AR into southern OK/northern TX. It was extremely subtle and slightly offset from the actual boundary, but if you looked just right you could see it (tried to get a good animation, but the contrast is lost so you’ll have to take my word for it…). The color table provided for these products, specifically the PW products, make identifying key/obvious boundaries easy, but the more subtle things are easily missed. I would caution anyone from using them for anything other than IDing the main players, unless the color table could be tweaked to enhance those low-to-mid range values (~0.4 to 0.8). I’m not sure it’s worth exploring given these products are 6km resolution, I was just surprised to see the subtle reflection of the outflow boundary. Perhaps I’ll play around with the color tables now…

–Stanley Cupp

NUCAPS vs. Obs

Posted in Live Blogs, News on by Brandon Smith.

Perfect conditions to utilize NUCAPS soundings today in the FWD CWA. FWD did a special release at 18z and I was able to compare that to a 19z NUCAPS sounding immediately west of FWD, ahead of the ongoing convection north and west of the CWA. They are remarkably similar from the boundary layer upward with very similar MUCAPE/SBCAPE values around 4600-4800 J/kg.

This highlights how important these NUCAPS soundings can be in the absence of any 18-20z special balloon releases. I’m very impressed with how well it lines up with the observed 18z launch and have more confidence in using these in pre-convective environments.

–Stanley Cupp

18z FWD sounding:

19z modified-NUCAPS sounding ~25 miles west of FWD

NUCAPS location (green dot above mouse cursor) vs. FWD location (yellow home cursor) and 1 minute vis imagery

Today’s Experimental Operations – May 1, 2019

Posted in Live Blogs, Operations Status Message, Outlooks on by Brandon Smith.

Today’s operations will be focused over the OUN (Norman), SJT (San Angelo), and FWD (Dallas/Fort Worth) county warning areas.  We are highlighting operations south of a remnant outflow boundary that has been left from storms that occurred overnight/early this morning roughly in the area of the Red River Valley.  Storms are currently on-going at the start of operations, with a severe thunderstorm watch over the operations areas that stretches from central OK all the way down to SW Texas.  Supercells will be the primary storm mode to start but might transition to a linear system later in the operations period.  The main threats today are large hail and high winds but tornadoes are still possible (lower probabilities than yesterday though).

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Az Shear Case – 3/3/19

Posted in AzShear, News on by Brandon Smith.

The case above shows a situation where due to the orientation of the zero isodop compared to the radar location, AzShear values are surprisingly low considering the strength of the convergent signature that preceded tornado development.

The case above shows  different tornadic circulation developing, but this time to the south of the radar –  a different orientation of the convergent signature relative to the radar. In both of these first two cases, the eventual tornado had not touched down yet, but the AzShear values were quite different. Training on zero isodop and how its orientation relative to the radar affects AzShear should be created for users before this product is used operationally.

This image shows the first circulation a bit farther in time as the orientation of the convergence changed and AzShear value bins began to max out.

A case where using a color table with bins detracts from the usefulness of AzShear. There are two areas of high AzShear indicated, however very different things are going on in each of these locations. One is a strong tornado on ground the other is flanking line convergence. These two features should not have the same color if this product is to be used in operations. Consider a graduated color ramp with a high range instead of broad bins.
A case where the anticyclonic shear component is extremely prominent in AzShear. Are these regions useful for forecasters focusing on the tornado? Are they more of a distraction? They could be a distraction in some situations.

The two above images compare 0-2 AzShear (top) and single scan AzShear (bottom). Due to multiple sampling by multiple radars, it appears as though 4 different iterations of the squall line shear boundary are plotted. This renders the merged 6646data almost useless for interpretation purposes. The single scan data removes this issue. Also from these screen grabs, it appears as though the farthest east scan is coming from the KMX, the single scan site used here.

The two examples above show the benefits of single radar versus merged once again. The merged azshear core is several miles behind the circulation center at this time. The single radar data follows the current velocity scan as expected. In a time-sensitive warning operation scenario, knowing this I would likely use the single radar product exclusively.

 

-Dusty Davis

Az Shear Possibilities

Posted in AzShear on by Brandon Smith.

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

Cell merger – AzShear, CPTI and DMD comparison

Posted in Live Blogs, News on by Brandon Smith.

Gonna take a look at SC merger  noting two small SC storms WNW of KINX radar @ 2058UTC. Prob TOR with these storms ~ 25% at this time with generally weak AzShear with stronger northern storm.

2106 UTC – just before storm merger see uptick in Azshear (0-2 km) with slight increase in CPTI products (50-52 %).  DMD output not providing any useful information on these storms at this time probably.  ProbTor ~ 10%

After merger @ 2114 UTC although not much change in AzShear, CPTI probabilities do increase some to 55 to 60%. Note that only the XDMD mesocylone algorithm displays a mesocyclone icon at this time while legacy DMD products do not.

2126 UTC – ProbTor rapidly increased to 77% with marked increase in AzShear. CPTI products also near 70% (110 mph).  Now all three DMD products display icon by this time.  BUT the XDMD seemed to identify mesocyclone sooner than legacy products.  This was encouraging.

 

2142 UTC – looks like storm looses organization as inflow may have been disrupted. AZshear becomes elongated with CPTI values falling notably.   Encouraging to note the character of AzShear (became elongated ) was consistent with the less organized storm (velocity structure).  ProbTor falls to ~ 65%.  Note the xDMD algorithm did still correctly identify shear couplet (SRM not shown) where legacy algorithm fails.   XDMD performed much better and and had greater temporal continuity than legacy product in this example. In this more complex storm interaction example appeared XDMD was able to better identify and retain areas of shear/rotation compared to legacy.

-Quik TWIP

 

 

 

 

 

 

NMDA

Posted in News on by Brandon Smith.

It can be a bit hard to see from the color scale, but take a look at the bottom left screen. The NMDA is shown there. One thing that I have noticed about it is it was able to better track the Mesocylone compared with the normal one. However, I have not gotten to test this extensively yet.

Notice in the time-step below that the NMDA is the able to hold onto the mesocyclone when the normal one cannot.

South Beach