The animation above shows Himawari full-disk imagery from 2300 UTC on 1 April through 1140 UTC on 2 April and depicts a cluster of thunderstorms over the Pacific Ocean far to the northeast of Guam.  A particular challenge in diagnosing atmospheric events over the open Pacific is the lack of data.  In this case, a timely NOAA-20 overpass (around 0300 UTC), below, allowed for the use of NOAA-Unique Combined Atmospheric Processing System (NUCAPS) profiles to describe the atmosphere in and around this ongoing convection.

The toggles below shows Total totals index and Tropopause heights over the Pacific Ocean around Guam and northeastward over the developing convection.  Modest instability surrounds the convective cluster (TT values from 40-44);  somewhat more unstable air (TT > 46) is diagnosed to the northwest of the convection.   Tropopause heights surrounding the convection are high, around 200 mb.  Much lower tropopause heights are diagnosed over the northern part of the domain, and the more unstable TT values are in a region where the tropopause height is sloping.

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NUCAPS can also show you lapse rates within the atmosphere.  It is important when viewing lapse rates to consider that the vertical resolution of NUCAPS profiles is typically not greater than 10 layers within the tropopause.  The toggle above shows lapse rates from 925-700 mb; lapse rates from 850-500 mb are shown below. These domains are is a bit larger than the domain used in showing the tropopause height and Total Totals index above.  The 925-700 mb lapse rates show two regions:  relatively weak stability, with lapse rates around 5 or 6 C/km south of 30 N Latitude, and much stronger stability (Lapse rates closer to 3 C / km ) north of that latitude, to the east of Japan.

The 850-500 mb lapse rates similarly show two general regions:  not as stable south of 30 N, much more stable east of Japan.  There is a more concentrated region of lower stability, however, along the leading edge of the sloped tropopause, at 850-500 mb compared to 925-700 mb, and the 850-500 mb values show larger lapse rates in the air to the east of Japan.  This toggle shows the 925-700 and 850-500 mb lapse rates directly.

 

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This region of the Pacific Ocean is scanned by both the Advanced Himawari Imager (AHI) on JMA’s Himawari-8 satellite and the similar Advanced Meteorological Imager (AMI) on KMA’s GK2A satellite.  The animation below combines visible imagery from the two satellites at 0100, 0110, 0230 and 0400 UTC to create a pseudostereocopic image of the convection.

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Developing (and ongoing) thunderstorms are usually locations of turbulence. The CIMSS Turbulence product, shown below for the region from 0000 UTC to 0350 UTC, and available online here, does show elevated turbulence probabilities over the convection (located over the western part of the domain shown below).

Himawari-8 imagery in this blog post courtesy of JMA; GK2A imagery in the blog post courtesy of KMA. Thanks to Brandon Aydlett, WFO Guam, for alerting us to this interesting case.

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GOES-16 sea-surface temperatures on 1 April 2021 show a region of much cooler temperatures — values around 74ºF , green in the color enhancement used) — surrounded by warmer sea-surface temperatures (values in the mid-80sºF, yellows and oranges in the color enhancement) to the southwest of Nicaragua. Why does this cool region exist? Typically, cool ocean surface temperatures can originate via upwelling (Note in the image above cool temperatures along the Equator where persistent upwelling exists). Is the part of the ocean that is cool above affected by upwelling? Cool temperatures are apparent to the northwest as a result of oceanic upwelling from a Tehuano wind through the Chivela mountain pass (similar to this event from 2018). There is a similar gap in the mountains between Costa Rica and Nicaragua (link).  Perhaps a persistent wind through that gap during the past months initiated this cool patch.  As shown below, the cool patch has been quite persistent — it was apparent in mid-January.

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The animation above cycles through GOES-16 Visible Imagery (0.64 µm) at 1901 UTC as well as simultaneous observations (from NUCAPS) of Lapse Rates (925-700 mb and 700-300 mb) and Mixing Ratio (925-700 mb and 700-300 mb). Thermodynamic information from NUCAPS complements information about the atmosphere that can be inferred by the GOES-16 imagery.

There are very strong low-level (925-700) lapse rates around Missouri behind the cold front that stretches over the south.   The atmosphere there is also very dry.  The smaller lapse rates at higher altitudes (700-300) also are in a region of very dry air.   NUCAPS Soundings from Des Moines, Kansas City and St Louis show the inversion that exists between the steep low-level lapse rates and smaller upper-level lapse rates. There is a much smaller change in lapse rates over the southeastern United States, with small stability all through the troposphere.

NUCAPS thermodynamic fields also capture the relatively moist air within the cloud features in northeastern Iowa, with strong low-level lapse rates on either side of the cloud field there.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Shortwave Infrared (3.9 µm) images (above) displayed the thermal anomalies (clusters of hot pixels) associated with 2 wildfires burning in western South Dakota on 29 March 2021. One fire began just west of Rapid City around 1530 UTC — which forced some evacuations. A second fire began just north of Interstate 90 around 1730 UTC — which forced the closure of Interstate 90 between Kadoka and Murdo as strong northwesterly winds in the wake of a cold frontal passage (surface analyses) caused a rapid fire run to the southeast. The southern surge of cold air (lighter shades of gray) behind the cold front could also be seen in the Shortwave Infrared images; both fires began shortly before the arrival of the cold front.

Taking a closer look at the fire just west of Rapid City, a 4-panel comparison of GOES-16 Fire Temperature RGB, Shortwave Infrared, Fire Power and Fire Temperature Characterization products (below) showed that this was not a particularly large or hot fire, whose signature was sometimes obscured by clouds moving overhead.

===== 30 March Update =====

On the following day, GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Vegetation” (0.86 µm) and Day Land Cloud Fire RGB images (above) revealed the northwest-to-southeast oriented burn scar (darker gray pixels).

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