Lightning at a Football Game

September 29th, 2017 |

GOES-16 ABI Channel 13 (“Clean Window”, 10.3 µm) Infrared Imagery, 2202 UTC 28 September to 0302 UTC 29 September 2017 (Click to animate)

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

The National Football League football game between the destined-to-win Green Bay Packers and the woeful Chicago Bears was interrupted by lightning at the end of the First Quarter on Thursday 29 September 2017. The animation of GOES-16 “Clean Window” 10.3 µm infrared imagery, above, shows a cold front passing easily through the area (in much the same way that Aaron Rodgers passed through the Bears Defense). The slow (slow, but not as slow as the Bears’ Offense) animation, below, shows the coldest cloud top moving over Green Bay at around 0130 UTC. Note that there is a parallax shift in this image: the storm top is displayed north of its actual ground location.

GOES-16 ABI Channel 13 (“Clean Window”, 10.3 µm) Infrared Imagery, 2202 UTC 28 September to 0302 UTC 29 September 2017 (Click to animate)

The UW CIMSS ProbSevere product (from here, Click here for an updated version that includes ProbTor/ProbWind/ProbHail) includes Total Lightning (from the ground network) as one of its predictors, and the stepped animation below, showing 0100, 0115 and 0130 UTC, highlights the lightning-producing cell that delayed the game. The Probability of Severe weather (Severe being defined as a Tornado, Hail exceeding 1″ in Diameter, and/or winds exceeding 50 knots) was very small (though not as small as the Bears’ chances), but note that lightning flashes, 2-3 flashes per minute, are consistently observed.

NOAA/CIMSS ProbSevere, 0100, 0115 and 0130 UTC on 29 September 2017 (Click to enlarge)

A new-to-operations instrument that is on board GOES-16 is the Geostationary Lightning Mapper (GLM). Preliminary observations from this instrument, below, show that it too detected the lightning as it approached the stadium. The GLM pixel size is 8 kilometers at the sub-satellite point, a pixel size that is significantly larger than the GOES-16 ABI Pixel size (10.3 µm, with a pixel size of 2 km at the sub-satellite point, is shown below). Whereas ground-based lightning detection systems detect only cloud-to-ground lightning, the optical detectors on GLM detect both cloud-to-ground and in-cloud lightning. Typically, a cloud will produce in-cloud lightning before cloud-to-ground, so the GLM can alert a forecaster to potentially dangerous lightning with more lead-time than is possible with ground-based systems. The animation below starts with the first detection at 0030 UTC on 29 September, about 45 minutes before Lambeau Field was evacuated, and 10 minutes before ground-based sensors detected cloud-to-ground strokes. (the evacuation occurred at about 0115 UTC) Group Density is plotted on top of the GOES-16 10.3 µm ABI (the ABI has a grey-scale enhancement). Note the relatively large pixel size of the GLM, and the obvious parallax shift between the two fields. The strengths of the GLM for lightning safety at large outdoor events is obvious in this case.

GOES-16 ABI “Clean Window” (10.3 µm) Imagery and GLM Group Density, every 5 minutes from 0030-0130 UTC on 29 September 2017 (Click to animate)

Go Pack!!

Hurricane Maria downgraded to a Tropical Storm off the East Coast

September 26th, 2017 |
GOES-13 Infrared Window (10.7 µm) image, with Deep-Layer Wind Shear product [click to enlarge]

GOES-13 Infrared Window (10.7 µm) image, with Deep-Layer Wind Shear product [click to enlarge]

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

After its final 2 days of northward motion as a Category 1 storm well southeast of the Outer Banks of North Carolina, Hurricane Maria was downgraded to a Tropical Storm at 2100 UTC on 26 September 2017. A comparison of the 2345 UTC September GOES-13 (GOES-East) Infrared Window (10.7 µm) image and an overlay of the 00 UTC 27 September Deep-Layer Wind Shear product (above) showed that Maria had been moving northward into an environment of increasing northeasterly shear, aiding the decrease of storm organization and intensity. However, due to the large size of the strong wind field associated with Maria, surface wind gusts as high as 59 mph were reported along the Outer Banks.

The effect of increasing wind shear was obvious in the satellite presentation of GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) — the low-level circulation center (LLCC) was becoming more exposed with time, while deep convection remained southeast of the LLCC.

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images [click to play MP4 animation]

The entrainment of dry air into the northern semicircle of Maria was evident as a warming/drying trend depicted on GOES-16 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below).

GOES-16 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play MP4 animation]

GOES-16 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play MP4 animation]

Mostly Clear Skies over Puerto Rico

September 25th, 2017 |

Suomi NPP Day Night Band Visible (0.7 µm) Imagery, 0619 UTC on 25 September 2017 (Click to enlarge)

Mostly clear skies over Puerto Rico early on 25 September 2017 allowed the Day Night Band on Suomi NPP to observe man-made sources of light on that island as shown in the image above (Courtesy of William Straka, CIMSS).  (A previous example on this blog showed lights through clouds).  A similar view is available at NASA’s Worldview site, or at Real Earth. The Lunar Phase on 25 September 2017 is Waxing Crescent with 26% illumination; similar illumination occurred on 24 August, and a link to the Day Night Band imagery at NASA Worldview on that day is here. The differences are stark.

A RealEarth examination of two Suomi NPP VIIRS Day/Night Band (0.7 µm) images — an archived “clear sky” view from 31 December 2015, and an “after-Maria” image from 26 September 2017 (below) — provides a good before/after comparison showing a reduction in the amount of city light illumination following the passage of the hurricane.

Suomi NPP VIIRS Day/Night Band (0.7 µm) images: an  archived

Suomi NPP VIIRS Day/Night Band (0.7 µm) images: an archived “clear sky’ view from 31 December 2015, and a “after-Maria” image from 26 September 2017 [click to enlarge]

The Infrared Imagery, below, suggests a few clouds over northwest Puerto Rico. Such clouds could alter the perception of light sources in that region.

Suomi NPP VIIRS Infrared (11.45 µm) Imagery, 0619 UTC on 25 September 2017 (Click to enlarge)

Maria: Tropical Storm Watch for the Outer Banks of North Carolina

September 24th, 2017 |
Track of Hurricane Maria [click to enlarge]

Track of Hurricane Maria [click to enlarge]

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

Hurricane Maria was downgraded to a Category 2 storm at 12 UTC on 24 September 2017 (above), when it was located about halfway between Miami and Bermuda.

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed a close-up view of the eye region of Maria during the daylight hours.

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images [click to play MP4 animation]

Due to the large size of the radius of Tropical Storm force winds, a Tropical Storm Watch was issued late in the day for the Outer Banks and adjacent inland areas of North Carolina (below).

NHC advisory

UPDATE: 12 hours later, much of the Tropical Storm Watch was upgraded to a Tropical Storm Warning.