The Japanese Meteorological Agency (JMA) has released the first imagery from the Advanced Himawari Imager (AHI) on Himawari-9. The image above, from 0240 UTC on 24 January 2017, is from Band 3 (the “Red” Band) that detects reflected solar radiation near 0.64 µm in the visible part of the electromagnetic spectrum. This band has the highest spatial resolution of the 16 AHI channels: 0.5 km at the sub-satellite point. (A similar image from Himawari-8 at 0250 UTC on 24 January 2017 is here; Himawari-8 does not produce imagery at 0240 UTC or 1440 UTC; satellite housekeeping occurs at those times).

Additional Himawari-9 band imagery from 0240 UTC on 24 January 2017 is available here. All imagery courtesy of JMA.

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A NOAA-18 AVHRR Infrared Window (10.8 µm) image (above) showed the signature of cold air (violet colors) settling into river valleys and other low-elevation terrain areas across the cloud-free interior of Alaska at 1916 UTC (10:16 am local time) on 18 January 2017. Note that there was a layer of clouds (warmer cyan colors) over much of the North Slope of Alaska; these clouds were acting to limit strong surface radiational cooling, with resulting surface air temperatures only as cold as the -20s F. This AVHRR image was about 1 hour before the low temperature at Fairbanks International Airport (PAFA) dropped to -51ºF (-46ºC) — the first low of -50ºF or colder at that location since 31 December 1999 (-53ºF). While these were certainly cold temperatures, in general most were several degrees warmer than the daily record lows for 18 January:

It’s cold over parts of Alaska, but it’s not approaching record low levels. Many of these records were set in 1947. #akwx @Climatologist49 pic.twitter.com/ssWq0ZhV09

— Rick Thoman (@AlaskaWx) January 19, 2017

Closer views centered on Bettles (above) and on Tanana (below) further highlighted the influence of terrain on the pattern of surface infrared brightness temperatures.

A comparison of re-mapped 1-km resolution NOAA-18 and “4-km” resolution GOES-15 (GOES-West) Infrared Window imagery (below) demonstrated the spatial resolution advantage of “Low Earth Orbit” (Polar-orbiting) satellites over Geostationary satellites, especially for high-latitude regions such as Alaska. As this plot shows, the true spatial resolution of a “4-km” GOES-15 Infrared image pixel over the interior of Alaska — where that satellite’s viewing angle or “zenith angle” from the Equator is about 74 degrees — is actually closer to 16 km. For the “2-km” Infrared imagery that will be provided by the GOES-R series ABI instrument, the spatial resolution over the interior of Alaska will be closer to 8 km.

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The cold continued across much of Alaska on 19 January, as seen on a NOAA-19 AVHRR Infrared Window (10.8 µm) image at 1519 UTC or 4:19 am local time (above). However with a lack of cloud cover over the central portion of the North Slope, surface air temperatures were much colder (in the -40s F) compared to the -20s F that were seen there on the previous day.

As was shown on the previous day, closer views centered on Bettles (above) and on Tanana (below) further highlighted the influence of terrain on the pattern of surface infrared brightness temperatures. On this day a layer of clouds (highlighted by the warmer cyan colors) covered the far eastern portion of the Tanana image below — note that surface temperatures in the Fairbanks area beneath these clouds were only as cold as the -30s F. Farther to the west, which remained cloud-free, the minimum temperature at Tanana was -59ºF.

Time series plots of surface weather conditions at Fairbanks, Tanana and Bettles during the 18-19 January period are shown below. Note that the surface visibility was periodically restricted 1 statute mile or less, due to ice fog, at all 3 locations.

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A series of 3 atmospheric river events brought heavy rainfall and heavy snowfall to much of California during the first 10 days of January 2017 (NWS San Francisco/Monterey | WeatherMatrix blog). Hourly images of the MIMIC Total Precipitable Water product (above; also available as a 33 Mbyte animated GIF) showed the second and third of these atmospheric river events during the 06 January – 11 January 2017 period, which were responsible for the bulk of the heavy precipitation; these 2 events appear to have drawn moisture northeastward from the Intertropical Convergence Zone (ITCZ)..

A relatively cloud-free day on 13 January provided a good view of the Sacramento Valley and San Francisco Bay regions. A comparison of Terra MODIS Visible (0.65 µm) and Near-Infrared  “Snow/Ice” (2.1 µm) images (above) showed that snow cover in the higher terrain of the Coastal Ranges and the Sierra Nevada appeared darker in the Snow/Ice band image (since snow and ice are strong absorbers of radiation at the 2.1 µm wavelength) — but water is an even stronger absorber, and therefore appeared even darker (which allowed the areas of flooding along the Sacramento River and its tributaries to be easily identified). A similar type of 1.6 µm Near-Infrared “Snow/Ice” Band imagery will be available from the ABI instrument on the GOES-R series, beginning with GOES-16.

Better detail of the flooded areas of the Sacramento River and its tributaries was seen in 250-meter resolution false-color Red/Green/Blue (RGB) imagery from the MODIS Today site — water appears as darker shades of blue, while snow appears as shades of cyan (in contrast to supercooled water droplet clouds, which appear as shades of white). In the corresponding MODIS true-color image, rivers and bays with high amounts of turbidity (tan shades) were evident; the offshore flow of sediment from a few rivers could also be seen.

 

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A surface low moving inland (3-hourly surface analyses) helped to produce widespread rain and snow across much of Oregon and southern Washington during the 10 January – 11 January 2017 period. 4-km resolution GOES-15 (GOES-West) Infrared images (above) and Water Vapor images (below) showed the development of a deformation band that helped to focus and prolong moderate to heavy snowfall over the Portland, Oregon area (accumulations | historical perspective). The GOES-15 images are centered at Portland International Airport (station identifier KPDX).

1-km resolution GOES-15 Visible (0.63 µm) images (below) during the last few hours of daylight on 10 January revealed the shadowing and textured signature of numerous embedded convective elements moving inland, which were helping to enhance precipitation rates (and even produce thundersnow at a few locations, a phenomenon which is very unusual for the Pacific Northwest).

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As clouds cleared in the wake of the storm, a comparison of 375-meter resolution Suomi NPP VIIRS true-color and false-color Red/Green/Blue (RGB) images viewed using RealEarth (below) revealed the extent of the snow cover; snow appears as shades of cyan in the false-color image, in contrast to clouds which appear as shades of white. [Note: with 5 inches of snow remaining on the ground, a new record low temperature was set in Portland on 13 January]

The fresh snowfall was also apparent in a 30-meter resolution Landsat-8 false-color RGB image (below) along the south face of Mount Hood (located about 98 miles or 158 km east of Portland). The ski slopes of Timberline Lodge and  Mount Hood Meadows received 13-14 inches of new snow during this event; the snow base depth at Timberline was greater than the average amount for this time of year.

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