Oceans such as the South Pacific can be a large data void. NOAA-20 NUCAPS profiles can be an important data source to define the state of the atmosphere. The image above shows NUCAPS Sounding Availability from the overnight pass over American Samoa; the largest island of American Samoa, Tutuila, is just west of 170^oW in image above. There are green circles just north and just south of Tutuila, signifying locations of NUCAPS profiles associated with successful retrievals. The toggle below compares those two profiles with the 1200 UTC rawinsonde launch (NSTU) from Pago Pago. Good agreement is apparent, although the NUCAPS profiles are smoother.

The environment is somewhat dry. This is confirmed by a MIMIC Total Precipitable water mapping, shown below (for 1200 UTC on 19 April 2022) in an image taken from here. The Samoan islands are between two bands of moisture.

NUCAPS profiles give useful information, but it can be cumbersome to view all individual profiles sequentially. Gridded fields of various properties are available in AWIPS (and online here and here). The toggle below shows a larger view than the topmost image, and it compares gridded Temperature fields at 950 mb, and the 950-700 mb lapse rate. Over the Samoan islands, 950-mb temperatures are faily uniform around 23^o C, with “cooler” temperatures (closer to 21^o C) just to the northeast. Lapse rates are stable: between 4 and 5 ^oC/km. As you might expect given the relative dryness and stability, shower chances over American Samoa for 19 April are low.

Use NUCAPS when your weather is approaching from a region void of conventional data.

Imagery in this blog post was in part from the NOAA/TOWR-S instance of AWIPS in the Cloud. Thank you!

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The month-long animation above shows the Himawari-8 Sandwich Product (daytime, blending visible band 3 (0.64 µm) and Band 13 (10.41 µm); and nighttime: Infrared only (Band 13, 10.41 µm) ) for the period from 16 March 2021 through 16 April 2021 over the Pacific Island (1) sector from this site, courtesy of JMA. How has the tropical western Pacific changed over this month? During the first week, mid-latitude extratropical fronts move west to east across the northern part of the domain, brushing the northern Marianas Islands. The monsoon trough over the southern part of the domain shows a lot of activity from the start of an animation, although some periods show more activity than others (25-28 March is quiescent compared to times before and after). A cyclonic circulation moves westward to the south of Guam on 31 March/1 April. Then a stronger impulse moves into the domain from the east on 2-3 April. By 7 April, this tropical storm is south of Guam moving towards the northwest where it becomes Typhoon Malakas. An obvious eye is apparent in that system as it recurves to the west of Guam on 12-13 April. By the end of the animation (17 April), the system has lifted to the north/east of this domain, and the sector has only scattered convection.

Note in particular as the animation occurs how the region of Sun glint has shifted northward. Northern Hemisphere Spring is ongoing.

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GOES-16 “Clean” Infrared Window (10.35 µm) images, with time-matched SPC Storm Reports plotted in white [click to play animated GIF | MP4]

Overlapping 1-minute Mesoscale Sectors provided 30-second GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (above) — with time-matched plots of SPC Storm Reports — of thunderstorms that produced straight-line wind damage and hail as large as 4.25 inches in diameter across far southern Missouri and northeastern Arkansas after sunset on 15 April 2022. These storms intensified in the vicinity of a warm front that become quasi-stationary across the area (surface analyses). Following a storm damage survey (NWS Little Rock PNS), it was determined that damage at the reported tornado locations was caused by straight-line winds and wind-driven large hail.

Around the time of the first tornado/wind damage report (below), an area of warmer cloud-top infrared brightness temperatures (shades of orange) began to appear immediately downwind (southeast) of the cold overshooting top (cluster of black pixels) — suggesting the presence of an Above-Anvil Cirrus Plume (reference | VISIT training).

GOES-16 “Clean” Infrared Window (10.35 µm) image at 0030 UTC, with time-matched SPC Storm Report plotted in white [clic to enlarge]

The coldest GOES-16 cloud-top infrared brightness temperatures were around -70^oC, which was about 10^oC colder than the tropopause / equilibrium level temperature, as seen in a plot (source) of 00 UTC rawinsonde data from Little Rock, Arkansas (below).

Plot of rawinsonde data from Little Rock, Arkansas at 00 UTC on 16 April 2022 [click to enlarge]

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Suomi-NPP VIIRS Visible (0.64 µm) and Shortwave Infrared (3.74 µm) images [click to play animated GIF | MP4]

A sequence of Suomi-NPP VIIRS Visible (0.64 µm) and Shortwave Infrared (3.74 µm) images (above) revealed a long east-to-west oriented swath of horizontal convective roll (HCR) clouds associated with blowing snow and blizzard conditions across parts of the North Slope of Alaska on 15 April 2022. The plume of supercooled water droplet HCR clouds appeared warmer — lighter shades of cyan — due to enhanced reflection of incoming solar radiation   At reporting sites within the northern portion of the HCR clouds and blowing snow, winds were gusting in the 35-40 knot range and the visibility was often 1/2 to 1/4 mile.

A Suomi-NPP VIIRS SnowCloud RGB image at 1624 UTC (below) showed that this plume of HCR cloud features — which was mixed with blowing snow — crossed the coast of northwestern Alaska and extended several miles westward  across nearshore waters of the Chukchi Sea.

Suomi-NPP VIIRS SnowCloud RGB image at 1624 UTC (credit: Jason Ahsenmacher, NWS Fairbanks) [click to enlarge]

GOES-17 Near-Infrared Snow/Ice (1.61 µm) images created using Geo2Grid (below) showed how the HCR cloud plume evolved during the day.

GOES-17 Near-Infrared Snow/Ice (1.61 µm) images [click to play animated GIF | MP4]

Thanks to Jason Ahsenmacher, NWS Fairbanks, for bringing this interesting case to our attention!

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