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Hurricane Bud

By Scott Bachmeier •

East Pacific Hurricane Bud peaked at Category 4 intensity (ADT | SATCON) around 06 UTC on 12 June 2018 (just 4 days after Hurricane Aletta reached the same intensity) — and a GOES-16 (GOES-East) Mesoscale Sector was positioned over the storm about an hour before that time, providing “Clean” Infrared Window... Read More

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

East Pacific Hurricane Bud peaked at Category 4 intensity (ADT | SATCON) around 06 UTC on 12 June 2018 (just 4 days after Hurricane Aletta reached the same intensity) — and a GOES-16 (GOES-East) Mesoscale Sector was positioned over the storm about an hour before that time, providing “Clean” Infrared Window (10.3 µm) images at 1-minute intervals (above).

A post-sunrise comparison of 1-minute GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images is shown below.

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

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

Ocean Heat Content and Sea Surface Temperature analyses, with the track of Hurricane Bud ending at 12 UTC on 12 June [click to enlarge]

Ocean Heat Content and Sea Surface Temperature analyses, with the track of Hurricane Bud ending at 12 UTC on 12 June [click to enlarge]

As mentioned in the NHC discussion at 15 UTC, Bud was beginning to move over water having lower values of Ocean Heat Content and Sea Surface Temperature (above), which would lead to rapid weakening — in fact, an erosion of the northern eyewalll was seen in DMSP-16 SSMIS Microwave imagery at 1105 UTC (below).

DMSP-16 SSMIS Microwave (85 GHz) image [click to enlarge]

DMSP-16 SSMIS Microwave (85 GHz) image [click to enlarge]

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Mesoscale Convective System in the Plains

By Scott Bachmeier •

A Mesoscale Convective System (MCS) developed over eastern Nebraska early in the evening on 11 June 2018, then propagated southward across the Plains during the subsequent overnight hours. GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images with plots of SPC storm reports are shown above; a Mesoscale Sector was positioned over the region, providing images... Read More

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images, with plots of SPC storm reports [click to play MP4 animation]

A Mesoscale Convective System (MCS) developed over eastern Nebraska early in the evening on 11 June 2018, then propagated southward across the Plains during the subsequent overnight hours. GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images with plots of SPC storm reports are shown above; a Mesoscale Sector was positioned over the region, providing images at 1-minute intervals.

A closer look over Kansas using Infrared imagery from polar-orbiting satellites (below) revealed some very cold cloud-top infrared brightness temperatures, which included -87ºC on MODIS, -90ºC on VIIRS and -92ºC on AVHRR.

POES AVHRR, Terra/Aqua MODIS and Suomi NPP VIIRS Infrared images, with plots of SPC storm reports [click to enlarge]

Metop-B AVHRR, Terra/Aqua MODIS and Suomi NPP VIIRS Infrared images, with plots of SPC storm reports [click to enlarge]

The coldest air temperature on 00 UTC rawinsonde data from Dodge City and Topeka, Kansas (below) was -69.5ºC (at altitudes of 14.6 km/49,900 feet at Dodge City, and 17.6 km/57,700 feet at Topeka) — so in theory air parcels and cloud material within a vigorous overshooting top could have ascended a few km (or thousands of feet) beyond those altitudes to exhibit an infrared brightness temperature of -92ºC.

Plots of rawinsonde data from Dodge City and Topeka, Kansas [click to enlarge]

Plots of rawinsonde data from Dodge City and Topeka, Kansas [click to enlarge]

A toggle between re-mapped versions of the GOES-16 ABI and Metop-B AVHRR Infrared imagery over Kansas at the time of the very cold cloud-top infrared brightness temperature (below) revealed 2 important points: (1) with improved spatial resolution (1 km for AVHRR, vs 2 km *at satellite sub-point* for ABI) the instrument detectors sensed much colder temperatures (-92.6ºC with AVHRR vs -81.2ºC with ABI), and (2) due to parallax. the GOES-16 image features are displaced to the northwest. In addition to the isolated cold overshooting top in south-central Kansas, note the pronounced enhanced-V storm top signature in far northeastern Kansas.

Comparison of GOES-16 ABI and Metop-B AVHRR Infrared images [click to enlarge]

Comparison of GOES-16 ABI and Metop-B AVHRR Infrared images [click to enlarge]

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Cape Newenham, Alaska bow shock waves

By Scott Bachmeier •

GOES-15 (GOES-West) Visible (0.63 µm) images (above) showed patches of fog and low stratus moving southwestward off Southwest Alaska and across the adjacent offshore waters of the Bering Sea on 10 June 2018.A closer look using 250-meter resolution Terra/Aqua MODIS and 375-meter resolution Suomi NPP VIIRS true-color Red-Green-Blue (RGB) images... Read More

GOES-15 Visible (0.63 µm) images, with hourly plots of wind barbs [click to play animation]

GOES-15 Visible (0.63 µm) images, with hourly plots of wind barbs [click to play animation]

GOES-15 (GOES-West) Visible (0.63 µm) images (above) showed patches of fog and low stratus moving southwestward off Southwest Alaska and across the adjacent offshore waters of the Bering Sea on 10 June 2018.

A closer look using 250-meter resolution Terra/Aqua MODIS and 375-meter resolution Suomi NPP VIIRS true-color Red-Green-Blue (RGB) images from RealEarth (below) revealed a packet of “bow shock waves” created as the shallow fog/stratus interacted with the relatively rugged terrain of the narrow Cape Newenham land feature (Google Maps). Other examples of similar bow shock wave cloud features have been documented here, here and here.

Terra MODIS, Aqua MODIS and Suomi NPP VIIRS true-color RGB images [click to enlarge]

Terra MODIS, Aqua MODIS and Suomi NPP VIIRS true-color RGB images [click to enlarge]

A 30-meter resolution Landsat-8 false-color RGB image (below) provided a more detailed view of the bow shock wave structure. Snow cover (cyan) could be seen on some of the higher-elevation land features.

Landsat-8 false-color RGB image [click to enlarge]

Landsat-8 false-color RGB image [click to enlarge]

A time series plot of Cape Newenham surface observations (below) showed the fluctuations in visibility as northerly winds brought patches of fog over the site.

Time series plot of Cape Newenham surface observations [click to enlarge]

Time series plot of Cape Newenham surface observations [click to enlarge]

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PyroCumulonimbus cloud in Colorado

By Scott Bachmeier •

GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the formation of a small pyroCumulonimbus (pyroCb) cloud spawned by the 416 Fire in southwestern Colorado on 09 June 2018. A Mesoscale Domain Sector was positioned over the region, providing images at 1-minute intervals.On Shortwave Infrared imagery,... Read More

GOES-16

GOES-16 “Red” Visible (0.64 µm, left), Shortwave Infrared (3.9 µm, center) and “Clean” Infrared Window (10.3 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the formation of a small pyroCumulonimbus (pyroCb) cloud spawned by the 416 Fire in southwestern Colorado on 09 June 2018. A Mesoscale Domain Sector was positioned over the region, providing images at 1-minute intervals.

On Shortwave Infrared imagery, the thermal anomaly or “hot spot” appeared as a large cluster of red pixels — and the top of the pyroCb cloud took on a darker gray appearance than nearby high-altitude ice crystal clouds (due to enhanced solar reflectance off the smaller ice crystals of the pyroCb anvil). On 10.3 µm imagery, cloud-top infrared brightness temperatures cooled to around -50ºC (bright yellow enhancement) as the pyroCb drifted northeastward.

NOAA-19 AVHRR Visible (0.63 µm), Shortwave Infrared (3.7 µm) and Infrared Window (10.8 µm) images, with plots of 22 UTC surface reports [click to enlarge]

NOAA-19 AVHRR Visible (0.63 µm), Shortwave Infrared (3.7 µm) and Infrared Window (10.8 µm) images, with plots of 22 UTC surface reports [click to enlarge]

On 1-km resolution NOAA-19 AVHRR Infrared Window (10.8 µm) imagery at 22:07 UTC (above), the minimum cloud-top brightness temperature was -53ºC — this temperature roughly corresponded to an altitude of 11.6 km according to 00 UTC rawinsonde data from Grand Junction, Colorado (below).

Plots of rawinsonde data from Grand Junction, Colorado [click to enlarge]

Plots of rawinsonde data from Grand Junction, Colorado [click to enlarge]


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