Polar Hyperspectral Soundings and High Plains Convection

April 29th, 2022 |
PHSnMWnABI CAPE estimates, 1700 UTC 28 April to 0300 UTC 29 April 2022 (Click to enlarge)

On 28 April, SPC’s convective outlook showed a small region of SLGT RSK over western Nebraska, with Marginal probabilities over most of Nebraska and Kansas (link to 2000 UTC outlook). The animation above shows hourly CAPE predictions from a 3-km version of the Rapid Refresh that is run hourly and initialized with Polar Hyperspectral Data (infrared and microwave, from Metop and from Suomi-NPP and NOAA-20) fused with GOES-16 ABI data, thereby using the strengths of ABI (fine spatial and temporal resolution) and Polar Hyperspectral Soundings (excellent spectral resolution). The animation above (a mix of initial fields — 1700 – 1900 UTC ; 1 – 4h forecasts from 1900 UTC; and 6-9h forecasts from 1800 UTC) shows CAPE developing over the High Plains and then rotating north into Kansas by 0300 UTC on 29 April 2022. A later forecast of CAPE, below, runs from 2100 UTC 28 April through 0600 UTC 29 April (showing initial fields at 2100/2200 UTC, then forecasts from 2200 UTC at 2300 UTC through 0400 UTC [i.e., 1-6h forecasts], followed by 8h and 9h forecasts from 2100 UTC on 0500 and 0600 UTC). By 0600 UTC, an axis of instability stretches from western Nebraska southeastward into central Kansas. The two forecasts show similar patterns.

PHSnMWnABI CAPE estimates, 2100 UTC 28 April to 0600 UTC 29 April 2022 (Click to enlarge)

The toggle below compares two forecasts for 0300 UTC, a 9-h forecast from 1800 UTC on 28 April, and a 5-h forecast from 2200 UTC on 28 April. The 5-h forecast is a bit less quick in moving the high CAPE values northward.

5-h and 9-h forecasts valid at 0300 UTC on 29 April 2022 (click to enlarge)

So, what happened? The toggle below compares the 6-h forecast from 2200 UTC, valid at 0400 UTC on 29 April, with the initial field for the 0400 UTC model run. As above, it appears that the forecast model from 2200 UTC was a bit too fast in moving the CAPE northward and eastward into Kansas/Nebraska. But overall there is very good agreement between the two fields.

PHSaABI CAPE at 0400 UTC 29 April 2022: a 6-h forecast from 2200 UTC 28 April 2022, and the initial field for the 0400 UTC model run (Click to enlarge)

The animation below shows PHSnABI CAPE fields hourly from 0400 – 0700 UTC (initial fields from 0400-0600; 1-h forecast at 0700), side by side with observed GOES-16 ABI Band 13 color-enhanced brightness temperatures. The convection that develops is along the edges of the CAPE; that is, it forms along the CAPE gradient in the model. Click here to view SPC Storm Reports from 28-29 April.

PHSnABI CAPE values, 0400-0700 UTC (left) and GOES-16 ABI Band 13 infrared (10.3 µm) imagery, 0401-0701 UTC 29 April 2022 (click to enlarge)

The animation below shows ABI Infrared Imagery overlain on top of the forecast CAPE field. This drives home to point that convection on this day occurred where the gradient of CAPE was outlined/predicted by this forecast model.

PHSnABI CAPE fields overlain with GOES-16 Infrared ABI Band 13 (10.3 µm) imagery, 0800-1200 UTC on 29 April 2022 (Click to enlarge)

PHSnABI data will be demonstrated at the Hazardous Weather Testbed in late May/Early June. Model output is available outside of AWIPS at this website. To view more blog posts on this project, click the ‘Hyperspectral’ tag below.

Ozone and the airmass RGB

December 13th, 2021 |
GOES_17 airmass RGB, 2200 UTC on 12 December 2021 (Click to enlarge)

A GOES-17 airmass RGB, above, shows a strong feature in the Gulf of Alaska. It’s common to associate the orange and purple regions within that polar feature (that is accompanied by cloud features consistent with very cold air aloft) with enhanced ozone. What products are available online to gauge the amount of ozone?

The OMPS instrument on board NOAA-20 (and on Suomi-NPP) senses in the ultraviolet (from 250-310 nm) to compute ozone concentration. (For more information on OMPS, refer to this document) The figure below, taken from this Finnish website, shows ozone concentration for the 24 hours ending at 0110 UTC on 13 December. A distinct maximum is apparent over the Gulf of Alaska. Note the northern terminus of the observations that are related to the time of year: there is little Sun north of 60 N. The data for this were downloaded from the Direct Broadcast site at GINA at the University of Alaska-Fairbanks. OMPS data are also available (from Suomi-NPP) at NASA Worldview.

To determine the time of the data in the image below, consult the NOAA-20 orbital paths here. This image (from that site) shows a NOAA-20 ascending overpass between 2235 and 2245 UTC over the Gulf of Alaska.

Daily Composite of Ozone concentration for the 24 hours ending 0111 UTC on 13 December 2021 (click to enlarge)

NOAA-20 also carries the Cross-track Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) instruments that are used to create NUCAPS vertical profiles; one of the trace gases retrieved in this way is ozone. The distribution of ozone (with values in regions where it was dark) from NUCAPS is shown below (from this website maintained by SPoRT), and it corresponds roughly with the OMPS estimates shown above.

Gridded NUCAPS estimates of ozone, 2217 UTC on 12 December 2021 (Click to enlarge)

Conclusion: The assumption that upper-tropospheric ozone values are large in regions where the airmass RGB is tinted red or purple is a good assumption, especially if other structures in the RGB — such as cumulus cloud development in the cold air — reinforce the idea that an intrusion of stratospheric air is occurring. The strong storm that this lowered tropopause is supporting is accompanied by a moist feed of air moving into central California, as shown below by MIMIC total precipitable water fields.

Total Precipitable Water, 2200 UTC on 12 December 2021 (Click to enlarge)

Gridded NUCAPS fields are being tested within RealEarth, as shown below. They should be generally available soon.

RealEarth Gridded NUCAPS estimates of ozone, 2217 UTC on 12 December 2021 (Click to enlarge)

Solar eclipse shadow in the Southern Hemisphere

December 4th, 2021 |

GOES-16 Near-Infrared “Snow/Ice” (1.61 µm) images (credit: Tim SchmIt, NOAA/NESDIS) [click to enlarge | MP4]

GOES-16 (GOES-East) Near-Infrared “Snow/Ice” (1.61 µm) images (above) showed the shadow of a total solar ecliipse in the Southern Hemisphere on 04 December 2021. Even though the 1.61 µm imagery is at a lower (1 km) spatial resolution, it provided better contrast than higher-resolution (0.5 km) 0.64 µm “Red” Visible imagery, helping to highlight the shadow (below). Note that the shadow passed over the Antarctic Peninsula.

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (credit: Tim Schmit, NOAA/NESDIS) [click to enlarge]

GOES-16 CIMSS True Color RGB images (below) provided another view of the eclipse shadow’s progression. 

GOES-16 CIMSS True Color RGB images (credit: Tim Schmit, NOAA/NESDIS) [click to play animated GIF | MP4]

In a 3-panel comparison of GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm) and Shortwave Infrared (3.9 µm) images (below), note that the lack of solar reflection within the eclipse shadow led to cooler 3.9 µm brightness temperatures (lighter shades of gray).    

GOES-16 “Red” Visible (0.64 µm, top), Near-Infrared “Snow/Ice” (1.61 µm, middle) and Shortwave Infrared (3.9 µm, bottom) images (credit: Tim Schmit, NOAA/NESDIS/ASPB) [click to play animated GIF | MP4]

The shadow was also apparent in GOES-17 (GOES-West) images (below).

GOES-17 Near-Infrared “Snow/Ice” (1.61 µm) images [click to play animated GIF | MP4]

A composite of POES AVHRR Visible (0.63 µm) swaths around 0700 UTC (below) showed the shadow extending southward across South Georgia and the South Sandwich Islands and reaching the coast of Antarctica. 

Composite of POES AHVRR Visible (0.63 µm) swaths [click to enlarge]

In addition, portions of the solar eclipse shadow could be seen in True Color RGB images from Suomi-NPP and NOAA-20, as viewed using RealEarth (below).

VIIRS True Color RGB images from Suomi-NPP and NOAA-20 [clck to enlarge]

This blog post discusses AMRC/AWS staff viewing the partial eclipse from Antarctica’s McMurdo Station.

Severe weather in Oklahoma, Texas and Louisiana

April 22nd, 2020 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed thunderstorms that produced a variety of severe weather (SPC Storm Reports) across far southern Oklahoma on 22 April 2020. These discrete supercell storms developed along a cold front associated with a low pressure system moving across the region (surface analyses).

GOES-16 Visible and Infrared images with plots of time-matched SPC Storm Reports are shown below.

GOES-16 "Red" Visible (0.64 µm, top) and "Clean" Infrared Window (10.35 µm, bottom) images, with plots of SPC Storm Reports [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.35 µm, bottom) images, with plots of SPC Storm Reports [click to play animation | MP4]

Farther to the southeast across eastern Texas, GOES-16 Visible and Infrared images (below) revealed a large and long-lived supercell thunderstorm that eventually moved eastward into Louisiana.

GOES-16 "Red" Visible (0.64 µm) and "Clean" Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 Visible and Infrared images with plots of time-matched SPC Storm Reports are shown below. An Above-Anvil Cirrus Plume was produced by this thunderstorm, and cloud-top infrared brightness temperatures were as cold as -80ºC (violet pixels). Early in its life cycle, after dropping hail of 1.0-2.0 inches in diameter, the supercell produced the fatal EF-3 Onalaska tornado.

GOES-16 "Red" Visible (0.64 µm, top) and "Clean" Infrared Window (10.35 µm, bottom) images, with plots of SPC Storm Reports [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.35 µm, bottom) images, with plots of SPC Storm Reports [click to play animation | MP4]

A toggle between 1-km resolution NOAA-19 AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images at 2338 UTC (below) provided a more detailed view of the Above-Anvil Cirrus Plume. The coldest cloud-top infrared brightness temperature in the region of the overshooting top was -84.7ºC.

NOAA-19 AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images [click to enlarge]

NOAA-19 AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images [click to enlarge]

Additional imagery of these storms is available on the Satellite Liaison Blog.