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Above-Anvil Cirrus Plumes in Texas

By Scott Bachmeier •

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed an interesting contrast in the character of Above-Anvil Cirrus Plumes (reference | VISIT training) over central Texas just before sunset on 02 June 2021. The northernmost AACP was generated by a single brief overshooting top (during the 0031-0041 UTC time period), but produced the most robust... Read More

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]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed an interesting contrast in the character of Above-Anvil Cirrus Plumes (reference | VISIT training) over central Texas just before sunset on 02 June 2021. The northernmost AACP was generated by a single brief overshooting top (during the 0031-0041 UTC time period), but produced the most robust “warm” (brighter shades of green) plume signature in the Infrared imagery. Other AACP signatures could be seen in the southern portion of that mesoscale convective system, but none of them exhibited such a notable warm infrared signature (in spite of prolonged periods of pulsing overshooting tops).

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 0034 UTC [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 0034 UTC [click to enlarge]

The coldest cloud-top infrared brightness temperature of the brief overshooting top was -71ºC at 0034 .UTC (above) — soon afterward, the infrared brightness temperatures within the “warm wake” immediately downwind of the overshooting top were generally in the -51ºC to -55ºC range, highlighted by the brighter green enhancement (below).

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 0050 UTC [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 0050 UTC [click to enlarge]

A plot of 00 UTC rawinsonde data from Midland, Texas (below) indicated that the -71ºC overshooting top brightness temperature corresponded to a Most Unstable air parcel ascent of about 1 km beyond its Equilibrium Level. The warming temperature within the lower stratosphere (just above the tropopause / equilibrium level) was also apparent.

Plot of 00 UTC rawinsonde data from Midland, Texas [click to enlarge]Plot of 00 UTC rawinsonde data from Midland, Texas [click to enlarge]

Plot of 00 UTC rawinsonde data from Midland, Texas [click to enlarge]

It should be mentioned that not all Above-Anvil Cirrus Plumes exhibit a warmer signature on Infrared imagery — depending on the ambient temperature profile just above the tropopause / equilibrium level, some plumes can appear colder (for example: Nov 2018, Sep 2019 and May 2020)

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Ice motion in Norton Sound, and an aircraft dissipation trail over the North Slope of Alaska

By Scott Bachmeier •

GOES-17 (GOES-West) “Red” Visible (0.64 um) images (above) showed the motion of ice within Norton Sound — inbound early in the day, transitioning to outbound later in the day — on 28 May 2021. This ice motion was likely driven primarily by tidal motions within the Sound; for example, a plot of tide height for Unalakeet... Read More

GOES-17 “Red” Visible (0.64 um) images [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-17 (GOES-West) “Red” Visible (0.64 um) images (above) showed the motion of ice within Norton Sound — inbound early in the day, transitioning to outbound later in the day — on 28 May 2021. This ice motion was likely driven primarily by tidal motions within the Sound; for example, a plot of tide height for Unalakeet (below) depicted rising tide (water moving into the Sound) from 04-20 UTC followed by falling tide (water moving out of the Sound) after 20 UTC.

Plot of tide height at Unalakeet, Alaska on 28 May [click to enlarge]

Plot of tide height at Unalakeet, Alaska on 28 May [click to enlarge]

Farther inland over the Alaska North Slope, comparisons of Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images at 1838 and 2015 UTC (below) revealed the formation and subsequent expansion of an “aircraft dissipation trail”. As an aircraft — likely headed to or from Prudhoe Bay — flew through a relatively thin cloud layer composed of supercooled water droplets, it caused glaciation of supercooled water droplets along its flight path (which then fell out of the cloud as snow).

Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images [click to enlarge]

1-minute GOES-17 Day Cloud Phase Distinction RGB images created using Geo2Grid (below) showed the formation and growth of the aircraft dissipation trail.

GOES-17 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-17 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

===== 29 May Update =====

GOES-17 “Red” Visible (0.64 um) images, with plots of NAM12 model winds (green barbs) and Metop-A ASCAT winds (red bars) [ click to play animation | MP4]

GOES-17 “Red” Visible (0.64 um) images, with plots of NAM12 model surface winds (green barbs) and Metop-A ASCAT winds (red barbs) [click to play animation | MP4]

On the following day, 1-minute GOES-17 Visible images (above) showed a similar inbound/outbound diurnal shift in the direction of ice flow within Norton Sound. Plots of NAM12 model surface winds and Metop-A ASCAT surface scatterometer winds indicated that the ice motion was generally orthogonal to surface wind direction — which reaffirmed that tides were the primary factor influencing ice motion during those 2 days.

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Subtropical storm in the South Pacific

By Scott Bachmeier •

GOES-17 (GOES-West) “Red” Visible (0.64 um) images (above) showed the development of a subtropical storm in the South Pacific Ocean (just northeast of New Zealand) on 27 May 2021. Surface analyses from the New Zealand Met Service are available here.GOES-17 “Clean” Infrared Window (10.3 um) images (below) highlighted the curved band of cold-topped convection wrapping... Read More

GOES-17

GOES-17 “Red” Visible (0.64 um) images [click to play animation | MP4]

GOES-17 (GOES-West) “Red” Visible (0.64 um) images (above) showed the development of a subtropical storm in the South Pacific Ocean (just northeast of New Zealand) on 27 May 2021. Surface analyses from the New Zealand Met Service are available here.

GOES-17 “Clean” Infrared Window (10.3 um) images (below) highlighted the curved band of cold-topped convection wrapping into the deepening storm.

GOES-17 "Clean" Infrared Window (10.3 um) images [click to play animation | MP4]

GOES-17 “Clean” Infrared Window (10.3 um) images [click to play animation | MP4]

A NOAA-20 Infrared Window (11.45 um) image viewed using RealEarth (below) showed a higher resolution view of the band of cold clouds wrapping into the system at 1206 UTC.

NOAA-20 Infrared Window (11.45 um) image [click to enlarge]

NOAA-20 Infrared Window (11.45 um) image [click to enlarge]

With ample illumination from the Moon — in the Waning Gibbous phase, at 98% of Full — a Suomi NPP VIIRS Day/Night Band (0.7 um) image (below) provided a high-quality “visible image at night” at 1256 UTC (12:56 am NZST).

Suomi NPP VIIRS Day/Night Band (0.7 um) image [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 um) image [click to enlarge]

Suomi NPP ATMS Microwave (183.3 GHz) image

Suomi NPP ATMS Microwave (183.3 GHz) image (credit: Derrick Herndon, CIMSS) [click to enlarge]

A Suomi NPP ATMS Microwave (183.3 GHz) image (above) portrayed the spiral band wrapping into the core of the system at 1256 UTC, while a cross section of Suomi NPP ATMS Brightness Temperature anomaly (below) depicted the deep warm core (shades of green) characteristic of the subtropical cyclone.

Cross section of Suomi NPP ATMS Brightness Temperature anomaly [click to enlarge]

Cross section of Suomi NPP ATMS Brightness Temperature anomaly (credit: Derrick Herndon, CIMSS) [click to enlarge]

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Standing waves upstream of Nova Scotia

By Scott Lindstrom •

GOES-16 visible imagery above (click to animate) shows the development of standing waves upwind of southwestern Nova Scotia. These winds developed in a region of low-level southwesterly (i.e., onshore) flow, as shown in the 1806 UTC image below that includes surface observations.  Higher clouds are moving from a more westerly... Read More

GOES-16 Visible (Band 2, 0.64 µm) imagery, 1441 – 2126 UTC on 26 May 2021 (Click to animate)

GOES-16 visible imagery above (click to animate) shows the development of standing waves upwind of southwestern Nova Scotia. These winds developed in a region of low-level southwesterly (i.e., onshore) flow, as shown in the 1806 UTC image below that includes surface observations.  Higher clouds are moving from a more westerly direction, suggesting veering and warm-air advection.

Note the very warm temperatures over interior Nova Scotia in the image below.  This suggests a strong inversion such as is necessary to trap energy that is then manifest as the standing waves.  Indeed, the Yarmouth, NS sounding at 1200 UTC shows surface temperatures near 12 C with temperatures closer to 20 C between 900 and 950 mb;  that works out to be a potential temperature difference of 16.5 K across the inversion.

GOES-16 Band 2 Visible (0.64 µm) imagery at 1806 UTC along with 1800 UTC METAR observations. (Click to enlarge)

(Thanks to Richard DiMaio, Lewis University, for bringing this event to our attention!)

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