Hurricane Dorian reaches Category 5 intensity

September 1st, 2019 |

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

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 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 1200 UTC [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 1200 UTC [click to enlarge]

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.

GOES-16 “Red” Visible (0.64 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

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.

Mid-layer Wind Shear product, 00-15 UTC [click to enlarge]

Mid-layer Wind Shear product, 00-15 UTC [click to enlarge]


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).

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

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.

VIIRS True Color RGB and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 [click to enlarge]

VIIRS True Color RGB and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 [click to enlarge]


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.

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

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

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

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.

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

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

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

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.

MIMIC Total Precipitable Water and DMSP-16 SSMIS Microwave images at 21 UTC [click to enlarge]

MIMIC Total Precipitable Water and DMSP-16 SSMIS Microwave images at 21 UTC [click to enlarge]

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.

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]


Hurricane Dorian

August 28th, 2019 |

NOAA-20 Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, courtesy of William Straka (CIMSS) [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, courtesy of William Straka (CIMSS) [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (above) showed cold overshooting tops (darker black infrared enhancement) over the Leeward Islands as well as subtle mesospheric airglow waves propagating southward away from the center of Tropical Storm Dorian at 0606 UTC on 28 August 2019.

In a toggle between GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) and DMSP-18 SSMIS Microwave (85 GHz) images from the CIMSS Tropical Cyclones site (below), the Microwave image revealed a convective band that was wrapping around the northern portion of the center of Dorian at 0930 UTC.

GOES-16 "Clean" Infrared Window <em>(10.35 µm)</em> and DMSP-18 SSMIS Microwave <em>(85 GHz)</em> images [click to enlarge]

GOES-16 “Clean” Infrared Window (10.35 µm) and DMSP-18 SSMIS Microwave (85 GHz) images [click to enlarge]

1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (below) also showed a convective burst wrapping around the eastern and northern edges of the center of Dorian after 15 UTC. The coldest cloud-top infrared brightness temperature associated with that early convective burst was -83ºC.

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

Dorian was upgraded to a Category 1 Hurricane at 18 UTC. Prior to that time, the tropical cyclone had been moving through an environment of low deep-layer wind shear (below), one factor that is favorable for intensification. Dorian was also passing over water possessing warm sea surface temperatures and modest ocean heat content.

http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2019/08/.gifGOES-16 Infrared Window (10.35 µm) images, with contours of deep-layer wind shear at 19 UTC [click to enlarge]

GOES-16 Infrared Window (10.35 µm) images, with contours of deep-layer wind shear at 19 UTC [click to enlarge]

VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP as viewed using RealEarth are shown below, from around the time when Dorian was upgraded from a Tropical Storm to a Hurricane.

VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

VIIRS True Color RGB and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to enlarge]

A comparison of GOES-16 Infrared (at 2330 UTC) and GMI Microwave (at 2341 UTC) images (below) revealed Dorian’s small eye.

GOES-16 Infrared (10.35 µm) and GMI Microwave (85 GHz) images [click to enlarge]

GOES-16 Infrared (10.35 µm) and GMI Microwave (85 GHz) images [click to enlarge]

===== 29 August Update =====

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

On 29 August, 1-minute GOES-16 Visible and Infrared images (above) showed that periodic convective bursts persisted around the center of Category 1 Hurricane Dorian.

During one of those convective bursts from 1800-1900 UTC, an increase in GOES-16 GLM Flash Extent Density was evident (below).

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 Visible and Infrared images at 1852 UTC with and without an overlay of GLM Flash Extent Density are shown below. At that particular time, the overshooting top infrared brightness temperature reached a minimum value of -82.5C.

GOES-16 “Red” Visible (0.64 µm) image at 1853 UTC, with and without an overlay of GLM Flash Extent Density [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) image at 1852 UTC, with and without an overlay of GLM Flash Extent Density [click to enlarge]

GOES-16 “Clean” Infrared Window (10.35 µm) image at 1853 UTC, with and without an overlay of GLM Flash Extent Density [click to enlarge]

GOES-16 “Clean” Infrared Window (10.35 µm) image at 1852 UTC, with and without an overlay of GLM Flash Extent Density [click to enlarge]

===== 30 August Update =====

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

The eye of Dorian became more well-defined in 1-minute GOES-16 Visible and Infrared images (above) during the morning hours on 30 August.

A DMSP-17 Microwave (85 GHz) Microwave image at 1141 UTC (below) did not yet show a completely closed eyewall structure at that earlier time.

DMSP-17 SSMIS Microwave (85 GHz) Microwave image [click to enlarge]

DMSP-17 SSMIS Microwave (85 GHz) Microwave image [click to enlarge]

Dorian was upgraded to a Category 3 hurricane at 18 UTC — the storm was moving into a narrow corridor of weaker deep-layer wind shear around that time. During the 3 hours leading up to 18 UTC, animations of 1-minute GOES-16 Visible and Infrared imagery — with and without an overlay of GLM Flash Extent Density — are shown below.

GOES-16 “Red” Visible (0.64 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

===== 31 August Update =====

30-second GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

30-second GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

Overlapping 1-minute GOES-16 Mesoscale Domain Sectors provided imagery at 30-second intervals — Visible and Infrared animations of the Category 4 hurricane from 1430-1900 UTC are shown above and below, respectively. A longer Visible animation from 1100-2259 UTC is available here (courtesy of Pete Pokrandt, AOS).

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

30-second GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

Fire at a Jim Beam bourbon warehouse in Kentucky

July 3rd, 2019 |

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Snow/Ice” (1.61 µm, left), Near-Infrared “Cloud Particle Size” (2.24 µm, center) and Shortwave Infrared (3.9 µm, right) images – GLM Groups are plotted in red on the 3.9 µm images [click to play animation | MP4]

GOES-16 (GOES-East) Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images (above) revealed nighttime thermal signatures of a fire at a Jim Beam bourbon warehouse in Versailles, Kentucky on 03 July 2019. The fire reportedly began to burn around 0330 UTC (11:30 PM EDT on 02 July); it was thought that the fire may have been started by a lightning strike — and GOES-16 GLM Groups did indeed portray lightning activity associated with thunderstorms that were dissipating over the area around that time.

The nighttime thermal signatures seen on near-infrared 1.61 µm and 2.24 µm images (brighter white pixels) result from the fact that those two ABI spectral bands are located close to the peak emitted radiance of very hot features such as volcanic eruptions or large fires (below).

Plots of Spectral Response Functions for ABI Bands 5, 6 and 7 [click to enlarge]

Plots of Spectral Response Functions for ABI Bands 5, 6 and 7 [click to enlarge]

The fire continued burning during the day — although it was frequently cloudy, the hot 3.9 µm thermal signature (darker red pixels) was apparent through occasional breaks in the cloud cover (below).

GOES-16 Shortwave Infrared (3.9 µm) images [click to play animation]

GOES-16 Shortwave Infrared (3.9 µm) images [click to play animation]

Record May snowfall in Duluth, Minnesota

May 9th, 2019 |


GOES-16 “Red” Visible (0.64 µm) images, with plots of surface weather type (yellow) and GLM Groups (red) [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the cloudiness associated with a midlatitude cyclone (surface analyses) that moved across the Upper Midwest on 08 May09 May 2019.  The system produced accumulating snowfall from extreme eastern South Dakota to central/northeastern Minnesota, northwestern Wisconsin and Upper Michigan — storm total accumulations were as high as 10.6 inches at Duluth, Minnesota (observations), 10.4 inches at Poplar, Wisconsin, 5.0 inches at Atlantic Mine, Michigan and 3.0 inches at Astoria, South Dakota (NOHRSC maps of snowfall/snowdepth). Note that the NW-SE oriented band of snowfall straddling the South Dakota/Minnesota border may have been enhanced by upslope flow as northeasterly surface winds encountered rising terrain of the Coteau des Prairies.

GOES-16 Mid-level Water Vapor (6.9 µm) images (below) showed the formation of a SW-NE oriented deformation zone across Minnesota — forcing for ascent was further aided by a stretched lobe of 500 hPa vorticity and 310 K potential vorticity that moved northeastward across the region during this period, along with a favorably-coupled 250 hPa jet streak configuration. Cloud features within the deformation zone across eastern South Dakota into southern/central Minnesota had an appearance resembling convective elements/bands in both the Visible and Water Vapor imagery.

GOES-16 Mid-level Water Vapor (6.9 µm) images, with plots of surface weather type (yellow) and GLM Groups (red) [click to play animation | MP4]

Although lightning was not widespread — and thunder was not explicitly reported in any first-order station observations — there were isolated small clusters of GOES-16 GLM Groups detected, first over northeastern, then central and finally over southwestern Minnesota between 2256 and 0036 UTC (below), indicating the presence of thundersnow.

GOES-16 “Red” Visible (0.64 µm) images, with plots of surface weather type (yellow) and GLM Groups (red) [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with plots of surface weather type (yellow) and GLM Groups (red) [click to enlarge]




Through occasional breaks in the clouds later in the day on 09 May, GOES-16 Day Cloud Phase Distinction Red-Green-Blue (RGB) images (below) revealed the stationary signature of fresh snow cover (darker green) across central to northeastern Minnesota and far northwestern Wisconsin (glaciating cloud tops also appear as shades of green).

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

===== 10 May Update =====

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 Visible images (above) showed two swaths of snow cover remaining across northeastern Minnesota (where reported snow depths were 1-2 inches) and northwestern Wisconsin (where reported snow depths were 4-5 inches) on the morning of 10 May.

Comparisons of GOES-16 Land Surface Temperature (LST) and Visible images at 1401 UTC and 1501 UTC (below) indicated that LST values were as much as 10ºF colder within the areas of snow cover (brighter shades of cyan) compared to adjacent bare ground.

GOES-16 Land Surface Temperature and “Red” Visible (0.64 µm) images at 1401 UTC [click to enlarge]

GOES-16 Land Surface Temperature and “Red” Visible (0.64 µm) images at 1501 UTC [click to enlarge]