![\"GOES-15](\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2016\/06\/160621_goes15_water_vapor_AK_anim.gif\")
<\/a>GOES-15 Water Vapor (6.5 \u00b5m) images [click to play animation]<\/p><\/div>GOES-15 (GOES-West)<\/em> Water Vapor (6.5 \u00b5m) images (above)<\/strong><\/em> showed the southeastward migration of an upper-level low across the North Slope and the eastern Brooks Range of Alaska during the 21 June – 22 June 2016 period. A potential vorticity (PV) anomaly was associated with this disturbance, which brought the dynamic tropopause<\/em> — taken to be the pressure of the PV 1.5 surface<\/strong><\/a> — downward to below the 600 hPa pressure level over northern Alaska. Several inches of snow<\/strong><\/a> were forecast to fall in higher elevations of the eastern portion of the Brooks Range.<\/p>\n With the very large satellite viewing angle (or “zenith angle”) associated with GOES-15 imagery over Alaska\u00a0 — which turns out to be 73.8 degrees for Fairbanks — the altitude of the peak of the Imager<\/strong><\/a> 6.5 \u00b5m water vapor weighting function<\/strong><\/a> (below)<\/strong><\/em> was shifted to higher altitudes (in this case, calculated using rawinsonde data from 12 UTC on 22 June, near the 300 hPa pressure level).<\/p>\n GOES-15 Imager water vapor (Band 3, 6.5 \u00b5m) weighting function [click to enlarge]<\/p><\/div>The ABI<\/strong><\/a> instrument on GOES-R<\/strong><\/a> will have 3 water vapor bands, roughly comparable to the 3 water vapor bands on the GOES-15 Sounder<\/strong><\/a> — 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 \u00b5m, green)<\/em> and 12 (7.4\u00a0\u00b5m, red)<\/em> 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<\/strong><\/a> instrument; an example of AHI water vapor imagery over part of Alaska can be seen here<\/strong><\/a>.<\/p>\n GOES-15 Sounder water vapor weighting function plots [click to enlarge]<\/p><\/div>As the system departed and the clouds began to dissipate on 22 June, GOES-13 Visible (0.63 \u00b5m) images (below)<\/strong><\/em> did indeed show evidence of bright white snow-covered terrain on the northern slopes and highest elevations of the Brooks Range.<\/p>\n GOES-15 Visible (0.63 \u00b5m) images [click to play animation]<\/p><\/div>A sequence of 1-km resolution POES AVHRR Visible (0.86 \u00b5m) images (below)<\/strong><\/em> 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.<\/p>\n POES AVHRR Visible (0.86 \u00b5m) images [click to play animation]<\/p><\/div>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<\/strong><\/a> (below)<\/strong><\/em>. The actual time of the satellite overpass<\/strong><\/a> on 22 June was 2134 UTC.<\/p>\n<\/a><\/a><\/a><\/a>