GOES-16 Band 2 (0.64 µm) visible imagery, 1900-2030 UTC rocking animation from 7 May 2020 (Click to animate)

Consider the rocking animation (if you click on it) of 1-minute visible imagery, above, showing the high plains of West Texas from 1900-2030 UTC on 7 May 2020. A dryline is present; can you predict from this imagery where convection will initiate? (Will it? Spoiler alert: Yes, and Yes!)

The Split Window Difference field shows the difference in brightness temperatures sensed at 10.3 µm and 12.3 µm. In clear skies, a distinct signal can be apparent along a dryline because of more water vapor absorption at 12.3 µm than at 10.3 µm. (A classic example is shown here, and discussed in this journal article) On 7 May 2020, however, abundant thin cirrus (which cirrus also has a very strong signal in the split window difference) masked much of the surface-based dryline signal.

GOES-16 Split Window Difference (10.3 µm – 12.3 µm) field, 1801-2056 Rocking animation, 7 May 2020 (click to animate)

On 7 May 2020, NOAA-20 overflew the high plains shortly at around 2000 UTC (map, from this site). Data from individual NUCAPS profiles (shown as green, yellow or red dots on the image below) can be interpolated to horizontal grids that allow for an easy presentation of thermodynamic features. Total precipitable water, below, derived from those individual vertical profiles, shows a gradient over west Texas, as expected when a dryline is present.  Any kind of impulse moving eastward from New Mexico will encounter an increasingly moist airmass as it traverses the Texas panhandle.

Gridded NUCAPS estimate of Total Precipitable Water, ca. 2000 UTC on 7 May 2020 (Click to enlarge)

How does NUCAPS gauge the instability of this airmass? Convective Available Potential Energy (CAPE) from the NUCAPS profiles is shown below.  A maximum in CAPE occurs just southwest of Childress, TX.  Perhaps this region of maximum instability is where the strong convection will initiate?

NUCAPS-derived Convective Available Potential Energy, ca. 2000 UTC on 7 May 2020 (Click to enlarge)

Note the NUCAPS sounding profile point that sits within the maximum in CAPE in the image above.  It is green — a color that denotes an infrared retrieval that converged to a solution.  That CAPE-filled vertical profile is show below.

NUCAPS Profile, ca. 2000 UTC on 7 May 2020 at 34.1 N, 100.4 W (Click to enlarge)

Animated visible imagery, below (at a 5-minute time step) — click here to see the animation at every minute) — shows initiation just after 2130 UTC near where the western gradient of the CAPE maximum sits at 2000 UTC.

GOES-16 Band 2 (0.64 µm) visible imagery, 1800-2156 UTC on 7 May 2020 (Click to animate)

The 2356 UTC 7 May 2020 Clean Window image, below, (toggled with the 2056 UTC image) shows the result of rapid development!

GOES-16 Band 13 (10.3 µm) infrared imagery, 2056 and 2356 on 7 May 2020 (Click to enlarge)

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GOES-16 ABI Band 13 (10.3 µm) Infrared Imagery, 1800 UTC on 7 May 2020 (Click to enlarge)

GOES-16 Clean Window imagery from 1800 UTC on 7 May 2020, above, suggests a frontal zone from the central Atlantic southwestward through the Florida Straits.  What products can be used to diagnose the moisture differences between the dry airmass over the southeast United States/Florida and the far moister airmass over the central and western Caribbean Sea?

Total Precipitable Water is a Baseline Level-2 GOES-16 Product that is produced in clear air, and the toggle of it, with the Clean Window Imagery (and also overlain on top of the Clean Window Imagery), below, shows abundant moisture to the south and east of Florida.  The cloud-free demand of this Level 2 product makes it difficult to determine exactly where the moisture gradient sits.

GOES-16 ABI Band 13 (10.3 µm) Infrared Imagery and Level-2 Total Precipitable Water Product, 1800 UTC on 7 May 2020 (Click to enlarge)

NOAA-20 overflew the east coast of the United States shortly after 1800 UTC on 7 May 2020 (map, from this site).  The gridded field of Total Precipitable Water that was derived from the different vertical profiles (shown below in a toggle with the TPW and the points) shows a tight gradient over central Cuba.

NOAA-20 NUCAPS Profiles and Derived Total Precipitable Water field, ca. 1800 UTC on 7 May 2020 (Click to enlarge)

A strength of the NUCAPS-derived TPW is that it is produced in regions of clear and cloudy skies because it can rely on microwave sounder data in regions where clouds prevent the infrared sounder from giving a complete solution. The toggle below compares the GOES-16 Total Precipitable Water (a global product that gives cloud-free values every hour) with the NUCAPS product that gives an image along the swath).  Both products give similar values of TPW.

GOES-16 Level 2 Total Precipitable Water and NUCAPS Total Precipitable Water, ca. 1800 UTC on 7 May 2020 (Click to enlarge)

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A cold front with ample moisture and instability ahead of it spawned numerous strong storms in the Southeast U.S. yesterday; particularly one long-lived supercell in South Carolina. A convolutional neural network model (CNN) was deployed in realtime on the 1-min GOES-16 mesoscale sector imagery. The model produces an “Intense Convection Probability” (ICP). The inputs for the model are the GOES-16 ABI 0.64 µm reflectance, 10.3 µm brightness temperature, and GLM flash extent density. It was trained to identify “intense” convection as humans do, associating features with intense convection such as strong overshooting tops, thermal couplets (“cold-U/V”), above anvil cirrus plumes (AACP), and strong cores of total lightning.

The animation below shows the ICP contours overlaid ABI 0.64 µm + 10.3 µm sandwich imagery, annotated with preliminary severe storm reports.

The long-lived supercell in South Carolina exhibited AACP and cold-U features, and produced numerous severe wind and hail reports (up to the size of tennis balls). While the NOAA/CIMSS ProbSevere models handled this storm well, the ICP ramped up on a couple of severe storms in northern Georgia before ProbSevere did. ICP for these cells exceeded 90% 15-18 min before ProbWind reached 50%. The ICP may be able to provide additional lead time and confidence to ProbSevere guidance for certain storms, utilizing spectral and electrical information from geostationary satellites. Incorporating ICP into ProbSevere is an active area of current research.

ProbSevere storm contours and MRMS MergedReflectivity for storms in GA and SC. The main or “inner” ProbSevere contour is shaded by the probability of any severe weather, while the outer contour is shaded by the probability of tornado, which appeared when that value was at least 3%, in this example.

An accumulation of ProbSevere storm centroids (white to pink squares, 50% –> 100%), NWS severe weather warnings, and SPC severe local storm reports from 12Z on May 5th to 12Z on May 6th [click to enlarge]

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ACSPO SSTs at 0620 UTC and 0710 UTC on 6 May 2020 (Click to enlarge). The 0620 UTC image is actually from Suomi-NPP, not NOAA-20 as labeled.

Visible Infrared Imaging Radiometer Suite (VIIRS) data from Suomi NPP and NOAA-20 can be used to create accurate sea-surface temperature (SST) fields using the Advanced Clear-Sky Processor for Ocean (ACSPO) algorithms.  The toggle above shows ACSPO SSTs over the Gulf of Maine from Suomi NPP (at 0620 UTC) and from NOAA-20 (at 0710 UTC) — orbital paths can be found here.  Waters over the Gulf of Maine are relatively warm (around 41ºF) compared to the very cold waters (about 38ºF) southeast of Nova Scotia!

VIIRS’ view of the Gulf Stream is shown below — with the colorbar range from 59º to 86º F (compared to 20º to 100º for the Gulf of Maine image above).  Warmest Gulf Stream waters are around 85º, but more uniformly near 82º F, with shelf waters near 74º F and tropical Atlantic waters near 77º.

ACSPO SSTs at 1855 UTC on 5 May 2020 (Click to enlarge).

VIIRS-based ACSPO SSTs are available via an LDM feed from CIMSS. Previous blog posts on ACSPO SSTs are here and here.

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