Polar Hyperspectral Modeling for a narrow line of convection

May 13th, 2022 |
PHSnABI 7-h and 1-h forecasts of CAPE valid at 2300 UTC on 13 May 2022 along with GOES-16 Derived CAPE overlaid with GOES-16 Band 13 Infrared (Band 13, 10.3 µm) imagery, GOES-16 Visible Imagery (Band 2, 0.64 µm) overlain with Radar imagery, and GOES-16 Visible Imagery alone (Click to enlarge)

A narrow ribbon of Slight RIsk was forecast for parts of the midwest on 13 Friday 2022, as shown below, and a few severe weather events occurred (SPC Storm Reports); they were well forecast. How did the Polar Hyperspectral Sounding forecast system perform on this day? The toggle above shows a 7-h forecast of CAPE (initialized at 1600 UTC and valid at 2300 UTC). It’s noteworthy that the forecast also shows a narrow corridor of instability. A similar toggle, but starting with the 0-h initial field of PHSnABI derived CAPE from the model at 2200 UTC, is here.

SPC Day 1 Outlook, 13 May 2022, issued at 2000 UTC (Click to enlarge)

The toggle below shows the 7-h forecast compared to the GOES-16 ABI Derived CAPE. A similar toggle, here, compares the 1-h forecast (initialized at 2200 UTC, valid at 2300 UTC) with the 2300 UTC Derived CAPE observed from GOES. The 7-h forecast below might be too far to the east; however, the developing convection associated with ribbon of instability is removed from the leading edge of the CAPE.

7-h forecast of CAPE from PHSnABI Modeling system and GOES-16 Derived Stability CAPE (overlain with GOES-16 ABI Band 13 Infrared imagery (10.3 µm) at 2300 UTC on 2300 UTC 13 May 2022 (click to enlarge)

Precipitation forecasts from this event (available at this website) are shown below, starting with two forecasts valid at 2300 UTC: a 3-h forecast from 2000 UTC and a 1-h forecast from 2200 UTC. They both show strongest convection over western IL, as observed. The 2000 UTC forecast also shows the break in convection over southern WI, also as observed.

PHSnABI forecasts of 1-h precipitation at 2300 UTC valid from initial times of 2000 and 2200 UTC on 13 May 2022 (Click to enlarge)
Accumulated 1-h precipitation from the PHSnABI model initialized at 2200 UTC on 13 May 2022; forecasts valid at 2300 UTC on 13 May, 0000 and 0100 UTC 14 May 2022 (Click to enlarge)

The PHSnABI modeling system accurately showed the corridor of instability over the Great Lakes, and convection did develop with this instability as observed. (Note: forecasts initialized before 1700 UTC did not produce precipitation; observations from the afternoon overpasses of NOAA-20 and Suomi-NPP perhaps supplied the necessary information leading to a better prediction of precipitation). Radar imagery over WI at 0054 UTC on 14 May 2022 is shown below. The initial (very narrow) line of convection did produce precipitation over Madison, but precipitation moved over Madison from the south after 0100 UTC.

Base Reflectivity at 0054 UTC on 14 May 2022 (click to enlarge)

Satellite-derived instability ahead of widespread severe winds over South Dakota and Minnesota

May 12th, 2022 |
GOES-16 Visible imagery, 1841 – 2356 UTC, 12 May 2022

Storm Reports from SPC for 12 May 2022, (also shown below), show an extraordinary number of severe wind reports over eastern South Dakota and western Minnesota. Visible imagery from the CSPP Geosphere site, above, shows the convective system responsible for the widespread winds lifting northeastward out of Nebraska and moving over the Missouri River Valley.

Storm Prediction Center Storm Reports, 12 May 2022 (click to enlarge)

The animation below shows Clean Window infrared imagery (10.3 µm) overlain on top of Clear-sky only GOES-16 Derived Convective Available Potential Energy (CAPE). CAPE values increase into the mid-2000s (J/Kg) as the convection lifts toward the South Dakota/Minnesota border: abundant instability is present.

GOES-16 Band 13 Infrared Imagery (10.3 µm) and GOES-16 Derived CAPE, 1821 – 2316 UTC on 12 May 2022 (Click to enlarge)

NOAA-20 overflew this area just after 1800 UTC, and the NUCAPS profiles derived from CrIS and ATMS on board that satellite tell a similar story of instability. Gridded fields of the 850-500 mb Lapse Rate, of Total Precipitable Water (TPW) and of the Total Totals Index, below, show a corridor of instability and moisture over extreme southeast South Dakota. Lapse rates are between 8 and 9o C/km, TPW values are near 1.5″, and Total Total Index values exceed 55! Convection moving towards this region and along this axis of instability would not be inhibited by the environment. NUCAPS Sounding Availability points shown in the image below are mostly green: the infrared retrievals converged to a solution.

Gridded Values of 850-500 mb Lapse Rate, Total Precipitable Water, and Total Totals Index, ca. 1830 UTC on 12 May 2022. Also shown: NUCAPS Sounding Availability points (click to enlarge)

What do the individual NUCAPS Profiles look like? Two lines of profiles over eastern Nebraska are shown below. Sounding readout values from NSharp in AWIPS show large MUCAPS values, and a very well-mixed atmosphere.

NUCAPS profiles over eastern Nebraska/southeastern South Dakota, at the points indicated, ca. 1840 UTC on 12 May 2022 (Click to enlarge)
NUCAPS profiles over central Nebraska, at the points indicated, ca. 1840 UTC on 12 May 2022 (Click to enlarge)

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

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GOES-18 “Red” Visible (0.64 µm) images, with time-matched SPC Storm Reports plotted in red [click to play animated GIF | MP4]

1-minute Mesoscale Domain Sector GOES-18 “Red” Visible (0.64 µm) images with time-matched plots of SPC Storm Reports (above) showed the northeastward propagation of the derecho — along with a second Mesoscale Convective System in its wake — as it produced wind gusts as high as 107 mph in South Dakota (at 2125 UTC), hail as large as 2.50 inches in diameter in Nebraska (at 0007 UTC) and several tornadoes. Note that this early GOES-18 imagery is preliminary and non-operational.

The corresponding 1-minute GOES-18 “Clean” Infrared Window (10.35 µm) images (below) extend a bit past sunset — and revealed pulsing overshooting tops as cold as -70 to -75ºC (white pixels embedded within areas of black).

GOES-18 “Clean” Infrared Window (10.35 µm) images, with time-matched SPC Storm Reports plotted in cyan [click to play animated GIF | MP4]

Stereoscopic views of convection using GOES-16 and GOES-18 visible data

May 11th, 2022 |
GOES-16 and GOES-18 imagery, 1920 – 2350 UTC on 11 May 2022

GOES-18 data in this post are preliminary and non-operational and beautiful. Because GOES-18 and GOES-16 nadir positions are separated by almost 15o of longitude (89.5o and 75.2o, respectively), they can be used (when remapped to the same projection, in this case using a beta version of geo2grid that supports GOES-18 imagery) to create pseudo-stereoscopic imagery. That is, if you cross your eyes when looking at the imagery, and focus on the image that appears in the middle of the two other images, a three-dimensional image can be viewed (Note: Not all human brains can do this). The image above shows convection on 11 May 2022 over Nebraska between 1920 and 2350 UTC.

Thanks to Tim Schmit, NOAA/ASPB, for supplying me with these images!

Using the Night Microphysics RGB and LightningCast probabilities to anticipate nighttime convection and Lightning

May 11th, 2022 |
Nighttime MIcrophysics RGB, 0616 – 0811 UTC on 11 May 2022 (click to enlarge)

The Nighttime Microphysics RGB, above, over central Wisconsin (that’s Green Bay at the northeastern edge, and southeast Minnesota/northeast Iowa over the southwestern part, of the animation), shows a field of low clouds stretching west-southwest to east-northeast. Note however, the occasional appearance of redder pixels within the field (as shown in this annotated image from 0806 UTC), especially in Wood and Portage counties (Click here for a map of Wisconsin counties). That kind of signal suggests that vertical cloud growth is occurring. Do you think convection will occur shortly? What about lightning?


NOAA-20 overflew this region shortly after 0730 UTC, and NUCAPS profiles would have become available in AWIPS at about the time of the end of the animation. What do they show? The image below shows 850-mb Temperature and the 850-500 mb lapse rates computed from gridded NUCAPS fields. The steepest lapse rates and strongest instability is centered on a NUCAPS profiles in central WI (in Adams County) which is just south of the band of clouds identifiable in the Night Microphysics RGB shown above: NUCAPS profiles show ample instability just south of this line (and winds are southerly: 0000 UTC Green Bay sounding).

850-mb Temperatures, 850-500 mb Lapse Rate, and Total Totals Index, 0730 UTC on 11 May 2022 (click to enlage)

The individual NUCAPS soundings in Adams County and Green Lake County, below, show very steep mid-level lapse rates.

NUCAPS Profiles in Adams County (left) and Green Lake County (right) at 0735 UTC on 11 May 2022 (Click to enlarge)

The GOES animation of Nighttime Microphysics above ended at 0811 UTC. What happened in the next 15 minutes? Note a continued development in the amount of reddish pixels! During these 15 minutes, radar is also showing increasing returns.

Nighttime Microphsyics RGB, 0811-0826 UTC on 11 May 2022 (Click to enlarge)

If convection is expected, lightning might also occur. Lightning Cast is a product in the NOAA/CIMSS ProbSevere portfolio, and it’s available online here, and a short training video is here. LightningCast probabilities for the same 15-minute span as above are shown below. Low probabilites are present until 0826 UTC. When do you think lightning might occur with this developing line?

LightningCast probabilities, 0811-0826 UTC on 11 May 2022 (click to enlarge)

The animation below follows the developing cells through the next 15 minutes — from 0826 to 0841 UTC. Nighttime Microphysics (overlain by radar: note the parallax shift, and also note the continued reddening of pixels in the RGB where convection is occurring) is on the left, and LightningCast Probabilities are on the right. Do you think lightning is imminent?

Nighttime Microphysics RGB overlain with 0.5 Base Reflectivity (left) and LIghtningCast Probability (right), 0826 – 0841 UTC (Click to enlarge)

The first GLM observations (with a CONUS time cadence of every 5 minutes) of lightning occurred at 0846 UTC, as shown in the animation of the Nighttime Microphysics RGB below. (Here is LightningCast at 0846 UTC).

Nighttime Microphysics RGB and GLM Flash Extent Density (FED), 0616 – 0851 UTC on 11 May 2022 (click to enlarge)

The animation below shows the NightMicrophysics RGB overlain with LightningCast Probabilities, from 0816 to 0846 UTC.

GOES-16 Nighttime Microphysics RGB with LightningCast Probabilities and GLM FED observations, 0816 – 0846 UTC on 11 May 2022 (click to enlarge)

Gridded NUCAPS fields for this blog post were created using the NOAA/TOWR-S Cloud Instance of AWIPS. Thank you! And here is a link to a presentation detailing how the Nighttime Microphysics RGB can be used in winter!