1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed Hurricane Dorian off the coast of South Carolina from 1116-1900 UTC on 05 September 2019. During this period, Dorian weakened from a Category 3 to a Category 2 hurricane — a plot of deep-layer wind shear from the CIMSS Tropical Cyclones site (below) showed that the storm was moving into an environment of increasingly unfavorable shear.

Dorian’s eye passed directly over EDISTO Buoy 41004; a combined plot of wind speed, wind gust, and air pressure is shown below.  Across the region, peak wind gusts were 98 mph and rainfall was as high as 10.19 inches.

A sequence of VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 as viewed using RealEarth are shown below.

===== 06 September Update =====

Dorian made landfall on Cape Hatteras, North Carolina around 1235 UTC on 06 September — 1-minute GOES-16 Infrared images (above) showed the eye moving northeastward across the Outer Banks. Peak wind gusts were as high as 110 mph, with rainfall amounts up to 13.74″.

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Kudos to Carl Jones (NWS Grand Forks) for spotting this vivid example of mesospheric airglow waves (reference) produced by severe thunderstorms that were responsible for a swath of hail across South Dakota from 0515-1010 UTC on 02 September 2019. In the toggles between VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from NOAA-20 (at 0740 UTC), Suomi NPP (at 0831 UTC) and NOAA-20 (at 0921 UTC), note that the epicenter of the circular gravity wave patterns appeared to be located west of the convection on the earliest NOAA-20 image and east of the convection in the later NOAA-20 image — this is due to parallax (since the vertically-propagating waves were likely at an altitude near 90 km). This parallax shift was more pronounced in the NOAA-20 images since the high-altitude waves were near the limb of those two satellite swaths. The Moon was in the Waxing Crescent phase (at only 6% of Full), so features seen on the Day/Night Band images were primarily illuminated by airglow.

Closer views centered on the convection are shown below. Cloud-top infrared brightness temperatures in both South Dakota and Nebraska were -70ºC and colder in the NOAA-20 images (which are mislabeled as Suomi NPP), and -80ºC and colder in the Suomi NPP image. Bright white “lightning streak” signatures associated with the thunderstorms were more apparent in these closer views.

Interesting! Day Night Band from #SuomiNPP and #NOAA20 #VIIRS early this morning caught stunning mesospheric gravity waves. But why they are so far displaced to the west from likely culprit convection in central SD and NE? Skeptical its due to parallax. @CIMSS_Satellite pic.twitter.com/ZmL1fcXB1L

— Carl Jones (@northflwx) September 2, 2019

GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (below) revealed the rapid development of an isolated hail-producing thunderstorm that generated the mesospheric airglow waves.

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Overlapping 1-minute Mesoscale Domain Sectors provided GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 30-second intervals (above) as Hurricane Dorian reached Category 5 intensity just east of Great Abaco Island in the Bahamas during the morning hours on 01 September 2019. West of Dorian, station Identifier MYGF is Freeport on Grand Bahama Island (which stopped reporting at 00 UTC on 01 September, due to evacuation).

As noted in the 15 UTC NHC discussion, the eye of Dorian was exhibiting a pronounced “stadium effect”, with a smaller-diameter surface eye sloping outward with increasing altitude (below).

GOES-16 Visible images with and without overlays of GLM Flash Extent Density (below) revealed that lightning activity began to ramp up within the eyewall region after 12 UTC.

A Mid-Level Wind Shear product (below) showed that Dorian had been moving through an environment of low shear — generally 10 knots or less — during the 00-15 UTC time period on 01 September.

Updating every 60 seconds at 500 meter resolution, GOES-East was able to view Hurricane #Dorian as it made landfall in the Bahamas.

Notice the outer cays and shallow water adjacent to Great Abaco Island within a relatively clear eye. pic.twitter.com/yS4SgIRzA6

— NWS Grand Forks (@NWSGrandForks) September 1, 2019

As pointed out by NWS Grand Forks (above), portions of the outer cays just east of Great Abaco Island could be seen in GOES-16 Visible imagery through breaks in the low-level clouds within the eye (below).

VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 as viewed using RealEarth are shown below, as the eye was moving over Great Abaco Island.

The eye of #Dorian has made a second landfall at 2 pm EDT (1800 UTC) on Great Abaco Island near Marsh Harbour. Maximum sustained winds were 185 mph at the time. This is tied for the strongest Atlantic hurricane landfall on record with the 1935 Labor Day hurricane. pic.twitter.com/O9hrotTTbS

— National Hurricane Center (@NHC_Atlantic) September 1, 2019

After moving slowly westward across Great Abaco Island, Dorian later became the first Category 5 hurricane on record to make landfall on Grand Bahama Island (below). Station identifier MYGF is Grand Bahama International Airport in Freeport, and MYGW is West End Airport.

===== 02 September Update =====

Prior to sunrise on 02 September, 1-minute GOES-16 Infrared images (above) showed Dorian moving very slowly — with a forward speed of only 1 mph — across the eastern end of Grand Bahama Island (as it remained at Category 5 intensity).

After sunrise, 1-minute GOES-16 Visible and Infrared images (below) showed that the eye of Dorian was finally beginning to move very slowly northwestward away from Grand Bahama Island. At the end of the animation (15 UTC), Dorian was downgraded slightly to a high-end Category 4 hurricane.

Suomi NPP VIIRS True Color RGB and Infrared images (below) provided a view of Dorian at 1817 UTC.

At 21 UTC, a comparison of MIMIC Total Precipitable Water and DMSP-16 SSMIS Microwave images (below) suggested that a tongue of drier air from the northwest and west was wrapping into the southern and southeastern portion of Dorian’s circulation.

A long animation of GOES-16 Infrared images (below) covers the 1.5-day period from 1200 UTC on 01 September to 2359 UTC on 02 September — and initially includes 30-second images from 1200-1515 UTC on 01 September. Dorian was rated at Category 5 intensity from 1200 UTC on 01 September until 1400 UTC on 02 September. Station identifier MYGF is Grand Bahama International Airport in Freeport.

I’ve compiled a list of some notable facts and records set by #HurricaneDorian so far at the link below:https://t.co/oS6AaDI5V1 pic.twitter.com/VaSrOOuSQE

— Philip Klotzbach (@philklotzbach) September 3, 2019

Additional satellite imagery and products are available from EUMETSAT.

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The periodic deleterious heating of the GOES-17 Advanced Baseline Imager (ABI) will reach a peak on 30 or 31 August 2019. The effects (in ABI bands 8-16) of the heating are manifest because the Loop Heat Pipe on the GOES-17 satellite does not operate at peak efficiency and cannot dissipate the heat that accumulates as the sun shines directly on the ABI instrument at night. The animation above shows full-disk imagery for all 16 bands on GOES-17 from 0750 UTC through 1640 UTC. Band 12 (9.6 µm) imagery is affected the most by the heating: data are unuseable from 1040 UTC to 1630 UTC; Band 10, the low-level water vapor channel at 7.3 µm is unuseable from 1050 UTC to 1620 UTC. Other infrared bands show different outages. Only Band 14 (11.2 µm) is mostly unaffected, although some striping is apparent between 1210 and 1330 UTC.

Other well-known artifacts are present in the animation. For example, a keep-out zone (or solar avoidance zone, sometimes also called the “Cookie Monster Effect”) is apparent moving across the northern 1/5th of the Globe; this image from 0910 UTC shows the feature. Satellite-Earth-Geometry means the Sun is near the limb of the Earth and the satellite sensors do not scan near the Sun. Stray Light is also present in the imagery. This shows up most distinctly in visible/near-infrared imagery, but its effects are also present in the 3.9 µm imagery.

The figure below, from this blog post, shows predicted maximum focal plane temperatures for each day.  In early September, a rapid cool-down in the peak temperature occurs as the GOES-17 satellite starts entering the shadow of the Earth during night times when it would otherwise be illuminated by the Sun.

This website shows comparisons between GOES-16 and GOES-17 for different bands, and includes observations of the focal plane temperature.  The animation below shows the steady increase in the maximum focal plane module (FPM) temperature in August and that warmth’s impact on the Band 12 observations:  there are longer and longer periods of time with no GOES-17 Band 12 data as you move through August (indicated by difference values that are off the chart).

A similar chart for Band 8 (6.19 µm) is shown below. Band 8 is not affected so severely by the Loop Heat Pipe. (Click here here for a similar chart for Band 14 (11.2 µm)).

The intra-band differences on the effects of the excess heat are shown here for values on 29 August for Bands 8 (6.19 µm), 12 (9.6 µm) and 14 (11.2 µm).

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