With the very large satellite viewing angle (or “zenith angle”) associated with GOES-15 imagery over Alaska — which turns out to be 73.8 degrees for Fairbanks — the altitude of the peak of the Imager 6.5 µm water vapor weighting function (below) was shifted to higher altitudes (in this case, calculated using rawinsonde data from 12 UTC on 22 June, near the 300 hPa pressure level).The ABI instrument on GOES-R will have 3 water vapor bands, roughly comparable to the 3 water vapor bands on the GOES-15 Sounder — the weighting functions for those 3 GOES-15 Sounder water vapor bands (calculated using the same Fairbanks rawinsonde data) are shown below. Assuming a similar spatial resolution as the Imager, the GOES-15 Sounder bands 11 (7.0 µm, green) and 12 (7.4 µm, red) would have allowed better sampling and visualization of the lower-altitude portion of this particular storm system. The 3 ABI water vapor bands are nearly identical to those on the Himawari-8 AHI instrument; an example of AHI water vapor imagery over part of Alaska can be seen here. As the system departed and the clouds began to dissipate on 22 June, GOES-13 Visible (0.63 µm) images (below) did indeed show evidence of bright white snow-covered terrain on the northern slopes and highest elevations of the Brooks Range. A sequence of 1-km resolution POES AVHRR Visible (0.86 µm) images (below) showed a view of the storm during the 21-22 June period, along with the resultant snow cover on 22 June. However, the snow quickly began to melt as the surface air temperature rebounded into the 50’s and 60’s F at some locations. The increase in fresh snow cover along the northern slopes and the highest elevations of the central and northeastern Brooks Range — most notably from Anaktuvuk Pass to Fort Yukon to Sagwon — was evident in a comparison of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from 17 June and 22 June, as viewed using RealEarth (below). The actual time of the satellite overpass on 22 June was 2134 UTC.
According to surface analyses from the Ocean Prediction Center, the storm was centered over Japan at 00 UTC on 11 December, and began rapidly intensifying later that day as it continued moving northeastward; it eventually deepened to a minimum central pressure of 924 hPa (27.29 inches of mercury) over the far southern Bering Sea at 06 UTC on 13 December. This equaled the analyzed minimum central pressure of Post-Tropical Cyclone Nuri in November 2014, which was one of the strongest storms on record in the Bering Sea.
Corresponding GOES-15 Water Vapor (6.5 µm, 4-km resolution) images (below) offered a slightly closer view of the intensifying storm. The unique satellite signature — resembling a curved scorpion tail — of a phenomenon known as a sting jet was seen to begin developing around 20 UTC on 12 December south of the Aleutian Islands. Several hours after the middle-tropospheric sting jet feature on water vapor imagery moved over Adak Island (PADK on the images) around 0130 UTC, sustained surface winds of 82 knots (94 mph) with gusts to 106 knots (122 mph) were recorded just after 09 UTC. According a Tweet from the Ocean Prediction Center, winds from the storm also produced wave heights of 63 feet.A time series of surface observations at Adak Island (below) indicated that the minimum station pressure of 939.0 hPa (27.73 inches of mercury) was recorded just after 04 UTC. Additional imagery from this event can be found on the RAMMB GOES-R Proving Ground Blog.
A better view of the offshore ice (as well as the ice in central Hudson Bay, northeast of the aforementioned mesoscale low) was provided by Suomi NPP VIIRS true-color and false-color images, visulized using the SSEC RealEarth web map server (below). In the false-color image, snow cover and ice appear as darker shades of cyan.A comparison of Canadian Ice Service analyses from 16 November and 23 November (below) showed the growth of the offshore ice along the western and northwestern edges of Hudson Bay, as well as the larger area of ice growing southward in the central portion of Hudson Bay during that 1-week period. The departure from normal images at the bottom indicated that ice concentration along the western and northwestern edges was well below normal (red), while the concentration of the large area of ice in central Hudson Bay was greater than normal (blue).
A more detailed view of the fire hot spots was provided by 375-meter resolution (mapped onto a 1-km AWIPS grid) Suomi NPP VIIRS 3.74 µm shortwave IR images (below; click to play animation).Many of the fires were burning in the general vicinity of the Utopia Creek, Indian Mountain airport (station identifier PAIM); a time series of surface observation from that site (below) showed that visibility was 1 mile or less due to smoke at times on 25 July. Daily composites of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images viewed using the SSEC RealEarth web map server are shown below.