Severe weather outbreak across the central US

March 28th, 2020 |

GOES- 16

GOES- 16 “Red” Visible (0.64 µm) images, with time-matched SPC Storm Reports plotted in red [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES- 16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed widespread events of severe weather (SPC Storm Reports) associated with a large occluding low pressure system and its frontal boundaries on 28 March 2020. The most significant tornado produced EF-3 damage as it moved through Jonesboro, Arkansas beginning at 2157 UTC.

The corresponding GOES-16 “Clean” Infrared Window (10.35 µm) images are shown below. The coldest cloud-top infrared brightness temperatures were in the -60 to -70ºC range (red to black enhancement).

GOES- 16 "Clean" Infrared Window (10.35 µm) images, with time-matched SPC Storm Reports plotted in purple [click to play animation | MP4]

GOES- 16 “Clean” Infrared Window (10.35 µm) images, with time-matched SPC Storm Reports plotted in purple [click to play animation | MP4]

A toggle between a Suomi NPP VIIRS Visible (0.64 µm) image (with plots of available NUCAPS soundings) and the Gridded NUCAPS CAPE values (below) revealed pockets of instability across the lower Mississippi River Valley in advance of the approaching cold front. Due to the presence of dense multi-layer cloudiness across much of Arkansas, there were no good (green) NUCAPS profiles available near Jonesboro (KJBR), except for a few microwave-only (yellow) soundings just to the south.

Suomi NPP VIIRS Visible (0.64 µm) image with plots of available NUCAPS soundings + Gridded NUCAPS CAPE [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) image with plots of available NUCAPS soundings + Gridded NUCAPS CAPE [click to enlarge]

A plot of 19 UTC rawinsonde data from Little Rock, Arkansas (below) indicated a CAPE value of 2836 J/kg.

Plot of 19 UTC rawinsonde data from Little Rock, Arkansas [click to enlarge]

Plot of 19 UTC rawinsonde data from Little Rock, Arkansas [click to enlarge]

Strong Tornado through Nashville Tennessee

March 3rd, 2020 |

GOES-16 Clean Window (10.3 µm) Infrared Imagery at 1-minute intervals, 0313 – 0722 UTC on 3 March 2020 (Click to play mp4 animation)

A long-track tornado moved through Nashville (north Nashville to Lockeland Springs then towards Lebanon) early in the morning on 3 March 2020. (ProbSevere for this event is also discussed in this blog post; A GLM View of the storm is here) The Band13 mp4 animation, above (Click here for an animated gif), from 0313 through 0722 UTC shows the long-lived storm forming over western Tennessee and rolling eastward into Nashville after midnight. As the storm approached Nashville, the storm top frequently showed isolated cold pixels (yellow in the enhancement) that are testament to the strong convection, and an above-anvil cirrus plume (AACP) might be there too. All of these structures are consistent with a tornadic storm. The 00 UTC Nashville Sounding shows a favorable environment as well.

1-minute GOES-16 Infrared images with plots of time-matched SPC Storm reports is shown below, covering the period 0300-0802 UTC. The color enhancement applied to those images is slightly different — and the pulsing overshooting tops are easier to see as highlighted with darker shades of orange.

GOES-16

GOES-16 “Clean” Infrared Window (10.35 µm) images, with SPC Storm reports plotted in red [click to play animation | MP4]

Shortly after the tornado passed through Nashville, NOAA-20 overflew Tennessee. The toggle below shows the GOES-16 ABI Band 13 (10.3 µm) infrared imagery, the NUCAPS Sounding Location, and the computed Total Totals Index from the NUCAPS thermodynamic information. Values exceeding 50 are south and west of the thunderstorm complex. NUCAPS soundings are showing a thermodynamically unstable environment.

GOES-16 ABI Band 13 (10.3 µm) Infrared Imagery along with NUCAPS Sounding Points and Gridded Values of Total Totals Index computed from NUCAPS Soundings (Click to enlarge)

The high-resolution VIIRS instruments on NOAA-20 gives a high-resolution view of the storm, as shown below.  The figure includes the 11.45 µm VIIRS I05 infrared imagery (from Real Earth) and also shows a 5-minute GLM Group Density accumulation with a profound maximum (values exceeding 250!) over Lebanon TN.  The morning NOAA-20 orbit on 3 March was to the east of Tennessee (source), so a parallax shift between the GLM data from GOES-16 and the VIIRS I05 data will occur.

Real Earth captures of 11.45 µm VIIRS I05 infrared imagery and GOES-16 GLM 5-minute Group Density, 0700-0705 UTC

A zoomed-out toggle between VIIRS I05 and the Day Night Band (below, courtesy William Straka, CIMSS), (Click here to view the I05 with a different enhancement) shows the storm to the east of Nashville.  The quarter New Moon (that was below the horizon) offered no clear view of the cloud tops, but lightning illumination is apparent.

NOAA-20 11.45 µm VIIRS I05 infrared imagery and Day Night Band 0.70 µm visible imagery at 0717 UTC on 3 March 2020 (Click to enlarge)

This long storm in a favorable environment was captured well by the NOAA/CIMSS ProbSevere product.  The animation below tracks the storm across much of northwest and north-central Tennessee.  Time-series plots of the radar object (#181389) associated with the Nashville tornado are here:  ProbTor (including components), ProbSevere (including components), and ProbSevere, ProbHail and ProbTor values.  The cyclic nature of the storm is apparent.  ProbSevere/ProbTor/ProbHail values were very high when the Nashville tornado was on the ground (around 0640 UTC).

NOAA/CIMSS ProbSevere display over northwest to north-central Tennessee, 0330 to 0730 UTC. (Click to enlarge)


A project spearheaded by Bill Smith Sr and Qi Zhang at Hampton University (they are also affiliated with CIMSS) takes Polar Hyperspectral (PHS) data and blends it with GOES-16 ABI data.  Those fields that exploit the high spectral resolution from sounders in polar orbit (such as IASI or CrIS) and the high spatial and temporal resolution from GOES are then input into numerical models.  Output is here.  The better representation of moisture fields in these fields can help a model better define where strong convection will or will not occur.  The animation below shows initial fields of the Significant Tornado Parameter from 0300 – 0800 UTC on 3 March 2020. Compare the animation to initial fields of STP in a model that does not include the assimilated hyperspectral data here.

Significant Tornado Parameter at initial model run times from 0300 through 0800 UTC on 3 March 2020 (Click to enlarge). The number of assimilated retrievals is indicated in red; no retrievals were assimilated at 0700 UTC, and the STP field was affected!

What did the forecast for 0600 UTC look like from this model that includes polar hyperspectral data?  That is shown below, with a series of model runs.  There is run-to-run variability, but overall the forecast simulations show a peak in the STP parameter near Nashville. (This PDF compares model runs with and without Polar Hyperspectral Data; adding the satellite data helps the model focus convection where it occurs, mostly because the moisture fields are more accurately defined).

Forecasts valid at 0600 UTC on 3 March 2020, initialized at 0000, 0100, 0200, 0300, 0400 and 0500 UTC (Click to enlarge)

Tehuano gap wind event

February 27th, 2020 |

GOES-16 Visible (0.64 µm) images, with plots of surface reports (yellow), ASCAT winds (violet) and surface analyses (cyan) [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images, with plots of surface reports (yellow), ASCAT winds (violet) and surface analyses (cyan) [click to play animation | MP4]

GOES-16 (GOES-East) Visible (0.64 µm) images (above) revealed a cloud arc which marked the leading edge of a Tehuano wind event — air behind a cold front plunged southward across the Gulf of Mexico during the previous day, crossed the mountains of Mexico through Chivela Pass (topography) , and emerged over the Pacific Ocean on 27 February 2020. Within the western portion of the gap wind flow, ASCAT winds speeds were as high as 32 knots at 1540 UTC — but closer to the coast the Ocean Prediction Center was initially forecasting an area of Storm Force winds (downgraded to Gale Force winds later in the day).

On a GOES-16 Visible image with plots of available NOAA-20 NUCAPS profiles (below), the location of one profile immediately offshore (Point 1) and another just ahead of the Tehauno cloud arc (Point 2) are highlighted.

GOES-16 Visible (0.64 µm) image, with plots of available NOAA-20 NUCAPS profiles [click to enlarge]

GOES-16 Visible (0.64 µm) image, with plots of available NOAA-20 NUCAPS profiles [click to enlarge]

A toggle between the NUCAPS profile immediately offshore (Point 1, at 15.39 N latitude 94.55 W longitude) and the profile just ahead of the Tehauno cloud arc (Point 2, at 7.29 N latitude 93.95 W longitude) is show below. Note that Total Precipitable Water values were 1.78 inches ahead of the cloud arc, compared to 1.16 inches immediately off the coast of Mexico where the dry gap winds were entering the Gulf of Tehuantepec.

NOAA-20 NUCAPS Temperature (red) and dewpoint (green) profiles for Point 1 and Point 2 [click to enlarge]

NOAA-20 NUCAPS Temperature (red) and dewpoint (green) profiles for Point 1 and Point 2 [click to enlarge]

In a comparison of Visible images from GOES-17 (GOES-West) and GOES-16 (GOES-East), haziness in the Gulf of Tehuantepec (best seen with GOES-16, due to a larger forward scattering angle) highlighted blowing dust that was being carried offshore by the strong gap winds.

“Red” Visible (0.64 µm) images from GOES-17 (left) and GOES-16 (right) [click to play animation | MP4]

GOES-16 True Color Red-Green-Blue (RGB) images created using Geo2Grid (below) provided a clearer view of the blowing dust plumes in the Gulf of Tehuantepec.

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 True Color RGB images [click to play animation | MP4]

VIIRS True Color RGB images from Suomi NPP and NOAA-20 as viewed using RealEarth are shown below.

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

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

Comparing Gridded NUCAPS data to model fields

February 24th, 2020 |

NUCAPS fields of 850-mb dewpoint Temperature toggled with NAM40 and RAP40 estimates at approximately the same time, ~1800 UTC on 24 February 2020 (Click to enlarge)

Gridded NUCAPS fields include 850-mb dewpoint temperature fields, and this blog post compares the NUCAPS fields to model fields, and this is part of an ongoing series of blog posts on these horizontal fields.  The imagery above compares NUCAPS fields at 850 mb with NAM40 and RAP40 data over the southeastern part of the United States.  Very dry air is indicated over the western Atlantic Ocean north and west of the Gulf Stream.  There is generally good agreement between the NUCAPS and model fields. Model fields appear dryer (or NUCAPS fields are more moist).  Model fields show a pronounced gradient over the upper midwest that, at this scan time, were too far west to be viewed by NUCAPS.  (Click here to view the NUCAPS points — green, yellow and red — for this time, to show something about the data that has been input into the gridded fields).

However, the following pass from NOAA-20 (click here to view NOAA-20 orbit paths) included midwestern data.  Again, the general good agreement is obvious, especially with regard to the placement of the gradient. Is the atmosphere as dry as the model suggests at 850 mb? That’s a hard question to answer given 1200 UTC Soundings at Omaha, Minneapolis/Chanhassen, and Green Bay.  Note that NAM12 and RAP13 data are being shown in this example;  they gave mostly the same answer as NAM40/RAP40 used above.

NUCAPS fields of 850-mb dewpoint Temperature toggled with NAM12 and RAP13 estimates at approximately the same time, ~1900 UTC on 24 February 2020 (Click to enlarge)