Severe thunderstorms in the Northeast US

July 1st, 2017 |

* GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing *

As noted in the Tweet above from NWS Gray/Portland ME, a record number of tornado warnings were issued by that office on 01 July 2017. According to their damage surveys, the tornadoes were rated EF-0 to EF-1, with some straight-line wind damage also seen. GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images with plots of SPC storm reports (below; also available as a 98-Mbyte animated GIF) displayed the overshooting tops and colder cloud-top infrared brightness temperatures associated with some of the thunderstorms. Note the significant offset between cloud-top features and storm reports — this is due to parallax from the large viewing angle of the GOES-16 satellite (which is positioned over the Equator at 105º West longitude).

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with plots of SPC storm reports in red on Visible, and in black on Infrared [click to play MP4 animation]

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with plots of SPC storm reports in red on Visible, and in black on Infrared [click to play MP4 animation]

A comparison of Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images at 1744 UTC (below) showed the early stages of convective development in far southwestern Maine, in addition to well-developed thunderstorms in eastern New York (which would later move northeastward to produce a swath of heavy rainfall that caused flooding at some locations).

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11..45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11..45 µm) images [click to enlarge]

Thunderstorm development was fueled by high amounts of moisture that had moved into the Northeast US, as shown below by the Blended Total Precipitable Water product (values in the 40-50 mm or 1.6-2.0 inch range) and the Blended Total Precipitable Water Percent of Normal product (with values in excess of 200%).

Blended Total Precipitable Water product [click to enlarge]

Blended Total Precipitable Water product [click to enlarge]

Blended Total Precipitable Water Percent of Normal product [click to enlarge]

Blended Total Precipitable Water Percent of Normal product [click to enlarge]

The hourly evolution of moisture was depicted by the MIMIC Total Precipitable Water product (below).

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

Legacy Atmospheric Profiles and Large Hail in Iowa

June 29th, 2017 |

GOES-16 Visible Imagery (0.64 µm) from 1902 through 2307 UTC on 29 June 2017. Woodbury County in Northwest Iowa is outlined in Magenta (Click to play animated gif)

GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing

Softball-sized hail fell in northwestern Iowa on Thursday afternoon, 29 June (Storm Prediction Center Storm Reports). The visible animation above, from 1902 to 2307 UTC, shows the rapid development of convection over far northeast Nebraska. Woodbury County in Iowa is outlined in the animation, the largest reported hail occurred in that county along the shores of the Missouri River; the location of the 4.25″ diameter hail is shown as the green box on this imageThis visible image closely corresponds to the time of the hail fall.

Since a GOES-16 Mesoscale Sector was positioned over the region, imagery was available at 1-minute intervals — a comparison of “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images is shown below. Plots of SPC storm reports are parallax-corrected to match the location of the storm-top features. The rapid growth of the storm that produced the 4.25″ hail was apparent in the Infrared data, which showed cloud tops cooling from around -45ºC at 2000 UTC to -65.5ºC at 2130 UTC (the time of the hail report). Cloud-top cooling rates were consistently 3ºC/5 minutes during this time. Also, in far northeastern Nebraska, a supercell thunderstorm produced an EF-1 tornado that tracked 14.4 miles along with hail up to 2.75 inches in diameter (NWS Omaha summary).

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with SPC storm reports plotted in red (on Visible) and black (on Infrared) [Click to play MP4 animation]GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with SPC storm reports plotted in red (on Visible) and black (on Infrared) [Click to play MP4 animation]

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with SPC storm reports plotted in red (on Visible) and black (on Infrared) [Click to play MP4 animation]

One of the GOES-16 Baseline Products available to forecasters includes a series of stability parameters derived from the ABI channels (and using GFS data as a first guess): Legacy Atmospheric Profiles or LAP (Online Source). These products are similar to those produced from the GOES Sounder on GOES-15. The LAP Lifted Index at 2100 UTC, below, from the GOES-16 Mesoscale Sector sited over the convection, shows a remarkable pool of instability (Lifted Indices less than -8ºC) in the region near the developing convection (which was in the wam sector of an approaching surface low). CAPE values were in excess of 2000 J/kg. More information on the Legacy Atmospheric Profiles products is available here (as part of the Satellite Foundation Course for GOES-R).

LAP Profiles can be an excellent tool for situational awareness when convection develops in clear or partly-cloudy regions.

GOES-16 Legacy Atmospheric Profile (LAP) estimate of Lifted Index, 2100 UTC on 29 June 2017 (Click to enlarge)

Severe thunderstorms producing strong winds and large hail in Wyoming, South Dakota, Nebraska and Kansas

June 28th, 2017 |

GOES-16 Infrared Window (10.3 µm) images, with SPC storm reports of wind and hail [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images, with SPC storm reports of wind and hail [click to play MP4 animation]

** GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing **

Clusters of severe thunderstorms developed over eastern Wyoming and the Nebraska panhandle during the afternoon on 27 June 2017, and increased in areal coverage and intensity as they moved eastward into the overnight hours. 1-minute interval Mesoscale Sector GOES-16 Infrared Window (10.3 µm) images with plots of SPC storm reports (above) showed a number of locations with wind gusts in excess of 60 mph — including 79 mph in Rapid City SD at 2341 UTC and 100 mph in Custer NE at 0200 UTC. Many of these high wind reports were in the general vicinity of thunderstorm overshooting tops, which exhibited cloud-top infrared brightness temperatures in  the -70 to -80º C range (black to white enhancement).

Rain/hail swath in Nebraska and Kansas

June 26th, 2017 |

** GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing **

As indicated in the Tweet above from NWS Hastings, GOES-16 imagery highlighted the presence of a narrow swath of rainfall and hail in the wake of a small thunderstorm that moved south/southeastward across the Nebraska/Kansas state line area on 26 June 2017.

A 3-panel comparison of GOES-16 Visible (0.64 µm), Snow/Ice (1.61  µm) and Shortwave Infrared (3.9  µm) images (below) revealed a subtle signature of the hail swath on the Snow/Ice images (where ice features appear as darker shades of gray: southern NE  | northern KS), while the Shortwave Infrared images showed that the hail and rainfall swathaccumulations in southern Kansas included 0.58″ at Clay Center and 0.49″ at Hebron — remained slightly cooler (lighter gray) as the adjacent dry land surfaces continued to warm during the early to middle afternoon hours. SPC storm reports listed hail of 1.75 inches in diameter in southern Nebraska and 1.25 inches in northern Kansas.

GOES-16 Visible (0.64 µm, left), Snow/Ice (1.61 µm, center) and Shortwave Infrared (3.9 µm, right) images, with hourly surface reports plotted in yellow and SPC storm reports of hail size plotted in red [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left), Snow/Ice (1.61 µm, center) and Shortwave Infrared (3.9 µm, right) images, with hourly surface reports plotted in yellow and SPC storm reports of hail size plotted in red [click to play MP4 animation]

Regarding the cooling seen associated with the rainfall/hail swath, a Land Surface Temperature (LST) product derived using Aqua MODIS data (below) indicated that LST values were generally in the upper 60s to upper 70s F within the narrow swath,  in contrast to LST values in the 90s to around 100º F adjacent to the swath.

Aqua MODIS Land Surface Temperature product, Visible (0.65 µm), Infrared Window (11.0 µm) and Shortwave Infrared (3.7 µm) images [click to enlarge]

Aqua MODIS Land Surface Temperature product, Visible (0.65 µm), Infrared Window (11.0 µm) and Shortwave Infrared (3.7 µm) images [click to enlarge]