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

Tropical Depression #4 formed in the tropical Atlantic on 5 July 2017 (Click here for National Hurricane Center advisories on the system). The Depression is not forecast to strengthen, and two GOES-16 products give evidence to its weakened state. The animation of GOES-16 Band 4 (1.38 µm “Cirrus Channel”), above, shows a general decrease in the high clouds associated with this system (located north of 10º North Latitude and between 40º and 50º West Longitude), meaning convection is not strong. A closer view reveals intricate cirrus transverse banding around the periphery of the system during the early part of the day. In addition, the 10.3 µm “Clean Window” image, below, overlain on top of the GOES-16 Baseline Total Precipitable Water (TPW) Product, shows dry air west of the circulation. A Saharan Air Layer (SAL) analysis from here that uses Meteosat data, shows dry air moving towards the system from the east as well (Link). A toggle between GOES-13 Infrared Window, Meteosat-10 SAL product, and MIMIC TPW imagery can be seen here.

Refer to the National Hurricane Center website, or the CIMSS Tropical Weather website, for more information on this sytem.

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

As seen on the map of SPC storm reports from 21 June 2017 (above), nighttime thunderstorms (during the pre-dawn hours of 22 June) produced a swath of hail (as large as 2.0 inches in diameter) that damaged emerging crops at some locations across eastern South Dakota and southwestern Minnesota (NWS Aberdeen summary).

Nearly 2 weeks later, on 04 July, the hail damage swath was still apparent on GOES-16 imagery. In a comparison of “Blue” Visible (0.47 µm), “Red” Visible (0.64 µm) and Near-Infrared “Vegetation” (0.86 µm ) images (below), the northwest-to-southeast oriented hail damage swath was best seen on the 0.64 µm imagery (in part due to its higher spatial resolution, which is 0.5 km at satellite sub-point); healthy vegetation is more reflective at 0.86 µm, so the crop-damaged hail swath appears slightly darker in those images.

A signature of the hail damage swath was also seen in Near-Infrared “Snow/Ice” (1.61 µm) and Shortwave Infrared (3.9 µm) images (below). The hail damage swath warmed more quickly on the 3.9 µm imagery — exhibiting a darker black appearance with time — compared to the adjacent fields of healthy crops.

Why was the hail damage swath also seen on the 1.61 µm “Snow/Ice” (Band 5) imagery? A look at the Spectral Response Functions for GOES-16 ABI  bands 3, 4, 5 and 6 — plotted with the reflectance of asphalt, dirt, grass and snow (below) — show that the 1.61 µm Band 5 happens to cover a portion of the radiation spectrum where there is a minor peak in grass relectance (denoted by the green plot).

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Regarding the warmer temperatures seen on GOES-16 Shortwave Infrared images, the 1-km resolution Aqua MODIS Land Surface Temperature product at 1738 UTC (above) revealed a 10º F difference between the warmer hail damage swath (which appeared to be about 100 miles in length) and adjacent fields of undamaged crops. A similar result was noted on 03 July by NWS Aberdeen (below).

Monitoring for fires using GOES-16 and noted area ~10F warmer than surroundings – dry/dead crops from the 6/22 Castlewood hailstorm #SDWX pic.twitter.com/d2AeYos84W

— NWS Aberdeen (@NWSAberdeen) July 4, 2017

A comparison of before (21 June) and after (02 July) Aqua MODIS true-color Red/Green/Blue (RGB) images from the SSEC MODIS Direct Broadcast site (below) clearly shows the hail damage path.

On 05 July a closer view of the hail scar was seen using a Suomi NPP VIIRS true-color RGB image from RealEarth (below).

Incidentally, on 02 July the Sentinel-2A satellite provided 10-meter resolution true-color imagery of the hail swath:

Meant to share this a while ago. Sentinel 2A passed over the area 7/2/17. Zoomed to Castlewood. Hires: https://t.co/9edCkrqXob #sdwx #mnwx pic.twitter.com/vqkSs4og6f

— Carl Jones (@northflwx) July 13, 2017

===== 07 July Update =====

The hail damage swath was also evident on a 30-meter resolution Landsat-8 false-color RGB image from 07 July:

Other examples of satellite-observed hail damage swaths can be seen here and here.

 

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We issued 7 Tornado Warnings today, the most we’ve ever issued in a single day or even a whole year until now! #mewx #nhwx pic.twitter.com/x8set1XxOi

— NWS Gray (@NWSGray) July 2, 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).

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).

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%).

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

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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 image.  This 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).

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.

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