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

May 28th, 2021 |

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.

Subtropical storm in the South Pacific

May 27th, 2021 |

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]

Standing waves upstream of Nova Scotia

May 26th, 2021 |

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!)

SAR winds with convection over Lake Superior

May 25th, 2021 |

GOES-16 Band 2 (0.64 µm, “Red Visible”) imagery, 2216 UTC on 25 May – 0126 UTC on 26 May 2021 (Click to animate)

GOES-16 visible imagery, above, shows a line of convection moving over Lake Superior late in the day on 25 May 2021. Merged MRMS Radar Reflectivity at 2340 UTC, below, (from this website) shows radar echoes approaching 45 dBz (at a fair distance from the radars being used to produce the imagery). What kind of surface winds are likely associated with this system in the middle of Lake?

Merged MRMS Reflectivity, 2340 UTC on 25 May 2021 (click to enlarge)

Synthetic Aperture Radar data from the Canadian satellite RADARSat Constellation Mission-3 (RCM3), below, (from this website), shows winds in excess of 50 knots. The winds show a bowing structure as well. RCM data are very useful in lake/oceanic regions where surface data are sparse.

RCM3 SAR Winds over Lake Superior, 2339 UTC on 25 May 2021 (Click to enlarge)