Heavy snow across southern Minnesota, northern Iowa and southern Wisconsin

April 18th, 2018 |

24-hour snowfall ending at 12 UTC on 19 April [click to enlarge]

24-hour snowfall ending at 12 UTC on 19 April [click to enlarge]

The map above shows a band of heavy snow that fell across southern Minnesota (as much as 11.0 inches), northern Iowa (as much as 12.0 inches) and southern Wisconsin (as much as 9.4 inches) on 18 April 2018.

Animations of 1-minute Mesoscale Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm), “Clean” Infrared Window (10.3 µm) and “Low-level” Water Vapor (7.3 µm) images (below) showed the formation of convective elements and banding along the southern edge of the colder cloud shield — snowfall rates were enhanced when these convective features moved overhead, and thundersnow was noted at some locations in northern Iowa and southern Wisconsin.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly surface weather type plotted in cyan [click to play MP4 animation]

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images, with hourly surface weather type plotted in yellow [click to play MP4 animation]

GOES-16

GOES-16 “Low=level” Water Vapor (7.3 µm) images, with hourly surface weather type plotted in cyan [click to play MP4 animation]

In south-central Wisconsin, Madison (KMSN) received 7.2 inches of snowfall, which set a new record for daily snowfall (and helped to make April the snowiest month of the 2017/2018 winter seeason). In addition, the daily maximum temperature was only 33 ºF, which was a record low maximum for the date. Over the southwestern part of the city, a cluster of GOES-16 Geostationary Lightning Mapper (GLM) Groups was detected from 1918 to 1919 UTC (below; courtesy of Dave Santek, SSEC) — the GOES-16 Visible image at that time did display a textured cloud top appearance characteristic of embedded convection across southern Wisconsin.

GOES-16 GLM Groups [click to enlarge]

GOES-16 GLM Groups [click to enlarge]

===== 20 April Update =====

GOES-16 true-color (daytime) and Infrared Window (10.3 µm, nighttime) images [click to play MP4 animation]

GOES-16 natural-color RGB (daytime) and Infrared Window (10.3 µm, nighttime) images [click to play MP4 animation]

A fast animation of GOES-16 natural-color Red-Green-Blue (RGB) images (above) revealed the rapid rate of snow melt — especially on 19 April — along the southern edge of the snow cover (where lighter amounts of snow fell). The effect of the high late-April sun angle also played a role in the rapid snow melt.

Using GLM data to monitor convective development

March 15th, 2018 |

GOES-16 Band 13 (10.3) “Clean Window” Infrared Imagery, 0815-1400 UTC, and GLM Group Density.

Strong convection developed on 15 March over the Pampas of Argentina and Uruguay, as shown above. Full Disk imagery is available only every 15 minutes, and considerable convective development is possible during the 15 minutes between scans. If a Mesoscale sector with 1-minute imagery is not over convection, Geostationary Lightning Mapper (GLM) data from GOES-16 can be used to monitor convection during the time interval between Full Disk Scans: GLM updates every minute. The 18-minute animation below (from Real Earth) includes 3 Full-Disk images and every-minute updates of GLM Group Density. Group Density between 0700-0715 shows no sign of diminishing.  It should not surprise that cloud-tops continue to expand and cool when the 0715 UTC ABI Imagery appears at the end of the loop.

Note:  When GOES-16 or GOES-17 (GOES-S achieved Geostationary Orbit on 12 March and became GOES-17) are operating under Mode 6 (vs. the present-day Mode 3), Full Disk imagery will be available every ten minutes vs. current fifteen minutes.

GOES-16 Band 13 (10.3) “Clean Window” Infrared Imagery, and GLM Group Density 0658-0717 UTC.

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!!

Rapid Intensification of Hurricane Maria just to the east of the Leeward Islands

September 18th, 2017 |

GOES-16 “Clean Window” Infrared 10.3 µm imagery, 1600-2017 UTC on 18 September 2017 (Click to animate). Note: The Label states GOES-17 in error, and the time annotation becomes stuck for a time.

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

Hurricane Maria underwent rapid intensification on 18 September as it moved through very warm waters to the east of the Leeward Islands. The animation of GOES-16 “Clean Window” Infrared Imagery (10.3 µm), above, shows the rapid development of a warm concentric eye between 1640 and 1940 UTC. The toggle below, between 1600 UTC and 2000 UTC, testifies to a great increase in organization and strength. Click here for an mp4 animation from 1400 UTC to 2100 UTC on 18 September showing the intensification in the Visible (0.64 µm) channel from ABI.

GOES-16 “Clean Window” Infrared 10.3 µm imagery, 1600 and 2017 UTC on 18 September 2017 (Click to enlarge). Note: The Label states GOES-17 in error.

The storm is in an environment of very low shear (below) and moving towards warm water that is quite deep as depicted by large values of Oceanic Heat Content (bottom). (Maps found at this site).

850-250 hPa wind shear, 1800 UTC on 18 September 2017 (Click to enlarge)

Oceanic Heat Content analysis, 1800 UTC on 18 September 2017. (Click to enlarge). Note the relative cool wake north of the Leeward Islands left behind by Hurricane Irma.

Geostationary Lightning Mapper (GLM) data over Maria for the two hours ending 2045 UTC on 18 September (from this site; click here for infrared imagery), shows lightning within the southern eyewall of the storm.

GLM Group Observations in 3-minute intervals plotted on top of GOES-16 Visible (0.64 µm) Imagery, 1830-2045 UTC on 18 September 2017 (Click to enlarge)

For more information on this dangerous storm, refer to the webpages of the National Hurricane Center, or to the CIMSS Tropical Weather website. People in the Leeward Islands in particular should pay close attention to this storm.