The animation above shows a progression of mid-tropospheric lapse rates between late on 4 March and late on 6 March 2022. The purple circles enclose regions of steep mid-level lapse rates; dotted purple circles show the location of the steep mid-level lapse rates in the previous image. This slow animation shows the progression of these steep lapse rates towards late-afternoon tornadic outbreaks, shown as the inset Storm Reports (5 March 2022 ; 6 March 2022) from the Storm Prediction Center.

Are the steep lapse rates picking up on Elevated Mixed Layers? Compare the NUCAPS plot at 0830 UTC on 5 March and the adjacent Skew-T from Dodge City Kansas at 1200 UTC on the 5th, shown below; or the NUCAPS plot from 0830 UTC on 6 March and the adjacent Skew-T from Amarillo at 1200 UTC on the 6th, shown at the bottom.

Consider viewing gridded NUCAPS estimates of Lapse Rates every morning as part of your situational awareness to determine whether an Elevated Mixed Layer might influence subsequent weather. Gridded NUCAPS fields are available here (A NASA SPoRT site) and here (a RealEarth site).

Many thanks to Chris Gitro, MIC at WFO Duluth, for discussions about this case!

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SPC (The Storm Prediction Center) issued a Convective Outlooks on 5 March 2022 (1630 UTC; 2000 UTC) showing an Enhanced Risk of Severe Weather over portions of southern Iowa. Preliminary Storm Reports for the day (link) showed tornadoes south of a line from southwestern Iowa to near Des Moines, starting near 2100 UTC. The animation above shows the Day Cloud Phase Distinction RGB and the derive Lifted Index as very strong convection (ultimately tornadic) develops over southwestern Iowa in a region where Lifted Index values are near -4.

NOAA-20 overflew the region of convective initiation at around 1930 UTC. Mid-tropospheric lapse rates (700-500 mb) are below. The stability diagnosis shows an unstable atmosphere. A diagnosis of the Total Totals index shows very large values — >50 — over southwestern Iowa and eastern Kansas. Convection in this airmass is likely to be strong.

The instability over eastern Kansas was also measured with a special radionsonde launch from Topeka at 2000 UTC, and that radiosonde is compared to a NUCAPS profile (close to Topeka in space and in time) below. Some aspects of the two profiles are similar.

What do other NUCAPS profiles look like over Iowa? The image below shows NUCAPS sounding availability points, and also 3 profiles at the points indicated. Steepest mid-tropospheric lapse rates are in the southern part of the domain. Recall that tornadoes were south of a line from the southwest corner of Iowa to Des Moines.

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Legacy Atmospheric Profiles from GOES-16 are available at points, and a benefit is that they are produced every 30 minutes, so that changes in atmospheric stability with time can be monitored. (This profiling capability will be greatly enhanced with the sounder instrument scheduled to fly on GEO-XO). The single profile above documents a very steep mid-tropospheric lapse rate just to the south of Des Moines. That same profile (2051 UTC) and one at the same point 30 minutes later (2121 UTC) are shown below.

1-minute @NOAASatellites #GOES16/#GOESeast Visible images with time-matched plots of SPC Storm Reports show the daytime portion of today's outbreak of tornadoes across Iowa: https://t.co/moafbzYpn9 #IAwx @NWSOmaha @NWSDesMoines pic.twitter.com/f5iZ5WkOXt

— Scott Bachmeier (@CIMSS_Satellite) March 6, 2022

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AWIPS imagery in this blog post was created using the NOAA/NESDIS TOWR-S AWIPS Cloud Instance.

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Fancy a swim in Lake Michigan today? Mostly clear skies early in the morning of 4 March allowed for a near-complete NOAA-20 VIIRS estimate of Lake Surface Temperatures, as shown above. The warmest surface waters were near 39^oF. AWIPS-ready tiles of ACSPO fields are available from CIMSS. The image below (from which the AWIPS tiles used above were subsected) shows the large geographic region available from the CIMSS direct broadcast. (Here is direct link to direct broadcast directory — available for about 6 days — containing VIIRS imagery from this pass).

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This blog post contains Suomi-NPP VIIRS imagery that was derived (using CSPP) from data downloaded at the Direct Broadcast site at CIMSS. That blog post suggests the need of a brightness temperature difference field from the I04 and I05 data that can be found in this (https://ftp.ssec.wisc.edu/pub/eosdb/npp/viirs/2022_03_03_062_0632/sdr) direct broadcast directory (direct link, available for about 6 days). The Sensor Data Record directory includes I04 and I05 hdf5 granules that McIDAS-V can read: SVI04_npp_d20220303_t0641201_e0642443_b53613_c20220303071038095682_cspp_dev.h5 and SVI05_npp_d20220303_t0641201_e0642443_b53613_c20220303071039605225_cspp_dev.h5 ; determining exactly which granule you want — there are 10 different granules in this particular directory — is partly trial and error and partly viewing the orbit path (here) and choosing wisely. Save those files into a directory; also save the ‘GITCO’ files (that is: GITCO_npp_d20220303_t0641201_e0642443_b53613_c20220303070838040363_cspp_dev.h5) that contain georeferencing for the Imager (‘I’) bands (similarly, GMTCO files contain georeferencing for the Moderate-resolution ‘M’ bands).

After starting up McIDAS-V, you want to load the data. Note above that I’ve clicked on JPSS Imagery, and navigated to the directory containing the downloaded data (that directory also includes the GITCO files for those granules, but you don’t see them here). I’ve chosen both I04 and I05 data files from one granule, observed from 06:41:20.1 to 06:42:44.3. Click on ‘Add Source’ in the lower right corner of the window. If you then expand ‘IMAGE’ under ‘Fields’, you’ll see both I04 and I05 Brightness Temperatures.

Next, under the ‘Data Sources:’ tab, click on ‘Formulas’. You will see a ‘Miscellaneous’ tab, and under that tab, a ‘Simple Difference a-b’ choice. Choose that and click ‘Create Display’ — this will pop up a window in which you can choose the a (in this case, I05 Brightness Temperature) and b (for this case, I04 Brightness Temperature). Subsect the portion of the granule that you want to display using shift-left click and drag — and — after clicking ‘create image’ — you end up with the image below (zoomed in).

There is some fine-tuning yet to do. Under the ‘Legend’ in the image above, right-click on ‘VIIRS 2022-03-03…’ to bring up the Control Window shown below. Slide the ‘Texture Quality’ from ‘Medium’ to ‘High’ (if you have a large image — much larger than this one! — that will test your machine’s RAM!)

Similarly, if you right-click (again!) under ‘Legend’ and ‘VIIRS 2022-03-03…’ to ‘Edit->Properties’, you can change the Layer Label to include more information, which I did, as shown in the image below. Finally, I edited the color table to highlight positive values (that is, where I05 – I04 Brightness Temperature Difference is between 0 and 2^o C) that might show where stratiform clouds are present. That result is shown below. Yellow in the enhancement shows no difference between the fields, blue is a brightness temperature difference of 2^o C. Are you obtaining a good signal of fog in the region of the very dense fog over southern Volusia County? I’d only ask what a ‘good signal’ is!

Imagery in this post was created using v1.8 of McIDAS-V (downloadable here). You can find further documentation on this here.

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