If you were restricted to just one satellite-based observation and had to describe a week of weather, what would you choose? Submitted for your consideration: Morphed microwave estimates of moisture. The animation above shows MIMIC estimates of total precipitable water (created by using GFS winds to morph individual swaths of MIRS TPW estimates) centered on Hawai’i from 29 November through 7 December. What do these fields show you? There is a general increase in moisture over the Hawai’ian islands from the end of November to 2 December, at which point a polar front associated with a strong southward moving extratropical cyclone moves through the islands, generating snow over the Big Island’s highest peaks. Subsequently, a westward-moving subtropical low develops and draws moisture up from the ITCZ, resulting in heavy rain over the island chain. By the end of the animation, dry air starts to move over the islands from the east.

MIMIC Total Precipitable Water fields are available here. A archive of all fields and various domains is here. Filenames are such that it’s relatively easy to create cron jobs that create animations showing the latest fields, for example here for the eastern Pacific, here for the western Pacific, and here for the southern Pacific.

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MIMIC Total Precipitable Water product [click to play animation | MP4]

As an anomalously-deep Kona low moved northwest of and then west of Hawai`i during the 04-07 December 2021 period, it began to tap moisture from the Pacific ITCZ and channel it northward across the islands — setting the stage for a prolonged heavy rainfall event (which produced the wettest December day on record at Honolulu). Hourly MIMIC TPW images viewed using RealEarth (above) showed the convergence of 2 northward-moving streams of ITCZ moisture, that then flowed across various portions of Hawai’i (located at the center of the images) from 00 UTC on 04 December to 00 UTC on 08 December.

Air Mass RGB images created using Geo2Grid (below) highlighted the southwestward migration of the Kona low (darker shades of red) as well as the northward motion of deep convection within the stream of ITCZ moisture.

GOES-17 Air Mass RGB images [click to play animated GIF | MP4]

In addition to the heavy rainfall across many of the islands, the high-elevation summits of Mauna Kea and Mauna Loa on the Big Island of Hawai`i also received accumulating snowfall — a signature of this snow cover (darker shades of magenta) was evident in GOES-17 Day Snow-Fog RGB images shown below.

GOES-17 Day Snow-Fog RGB images [click to play animated GIF | MP4]

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GOES-16 Night Fog BTD (10.3 – 3.9 µm) and Day Snow Fog RGB images [click to play animated GIF | MP4]

As cold arctic air moved across the still-unfrozen waters of Lake Sakakawea on 06 December 2021, a lake effect cloud plume was seen downwind (southeast) of the lake in GOES-16 (GOES-East) Night Fog BTD (10.3 – 3.9 µm) and Day Snow Fog RGB images (above).

In a comparison of NOAA-20 VIIRS True Color RGB, False Color RGB and Infrared Window (11.45 µm) images at 1925 UTC (below), the lake effect cloud plume was diminishing as winds across/along the lake became lighter — and the unfrozen portions of Lake Sakakawea appeared dark in RGB imagery, with surface infrared brightness temperatures in the 1 to 2ºC range (darker shades of orange).

NOAA-20 VIIRS True Color RGB, False Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

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A benefit of Polar Orbiters over northernmost Alaska is a wealth of NUCAPS soundings from NOAA-20! The animation above shows useful profiles near Utqiagvik AK (formerly Barrow) for the nine hours between 1132 and 2128 UTC on 5 December 2021. The vibrant green point is the point selected for the profiles shown below. Note that the profiles at 1633, 1810 and 1948 UTC were microwave-only; that is, the infrared retrieval did not converge (click here to see the distribution from 1633-1948 UTC; you’ll see yellow points in the region near Utqia?vik). The sounding availability suggests near-continuous (at 90-minute timesteps!) monitoring of the tropopshere during the day.

The animation below shows 4 profiles (for which the infrared solution converged in the retrieval); A consistent warming in the profiles is noted, and perhaps a slight drying as well. The tropopause is also shown to rise. These profiles are not reliant on numerical model data; they are an independent measure of the polar atmosphere. It’s important to view similar dot colors in this kind of animation. The animation at the bottom of the post includes in the animation the microwave-only profiles at 1635, 1914 and 1953 UTC. The IR+MW profiles below have far different character than MW-only profiles at bottom; however, the MW-only profiles also show a slow warming.

These NUCAPS profiles were displayed using a method that is detailed here, developed by scientists at STC and SPoRT. NWS forecasters who are interested in this functionality can contact the blog author.

Note that the high temperatures in Utqiagvik (Barrow) on 3, 4 and 5 December were 0º, 19º, and 25º F, respectively, entirely consistent with the warm advection depicted in the NUCAPS profiles.

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