Supercells in the Southeast

May 6th, 2020 |

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]

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]

ACSPO SSTs from Direct Broadcast data

May 6th, 2020 |

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.