Altimetric measurements of the sea surface (from this site), above, show a region of very tall waves early on 14 February, with Significant Wave Heights exceeding 30 feet. Those waves are also show below in an analysis from OPC (link); they are southwest of a hurricane-force low (surface analysis; here is a toggle between the Significant Wave heights and the surface analysis).

Forecast Waves, below, show the long wave period associated with the large waves starting to affect the Hawai’ian Islands by 1200 UTC 15 February. The north-facing shores of the Hawai-ian islands are under a High Surf Warning.

What does the satellite imagery show for the storm that supported such strong waves? Airmass RGB imagery from Himawari-9, below, (from 0000 UTC 9 February through 2300 UTC 12 February) show the development of the system and a long fetch of strong winds (by 2300 UTC 12 February). The strong storm exits the eastern edge of the domain by the end of the animation

GOES-West imagery (from the CSPP Geosphere site), hourly below from 1500 UTC on 12 February through 1900 UTC on 14 February shows the strong storm moving eastward across the Pacific, with strong nortwest winds inferred behind a propagating cold front.

For more information on this wave event, refer to the forecast office of the National Weather Service in Honolulu.

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GOES-16 Mid-level Water Vapor (6.9 µm) images with an overlay of GLM Flash Extent Density (above) showed that there were isolated brief periods of lightning activity over parts of West Virginia / Maryland / Pennsylvania during the nighttime hours, followed by more activity off the south coast of Massachusetts during the daytime hours on 13 February 2024. Although this lightning was occurring near areas receiving moderate to heavy snowfall, there were no METAR sites that explicitly reported thundersnow.

As clouds slowly began to clear, GOES-16 Day Cloud Type RGB images (below) began to reveal areas with appreciable snow cover (darker shades of green).

On the following day, with minimal cloud cover RGB imagery showed the areal extent of the swath of fresh snow cover that extended from West Virginia to Massachusetts (below). Notable snowfall accumulations included 15+ inches in Pennsylvania, New Jersey and Connecticut (storm summary).

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A sequence of Suomi-NPP VIIRS Infrared Window (11.45 µm) images (above) displayed the development of a coma-shaped cloud structure associated with a low pressure system near the North Pole (northwest of Greenland) on 13 February 2024. The single METAR surface report plotted is Svalbard, Norway (the reports for CWLT — Alert, Nunavut, Canada — were not available).

Analyses from the Canadian Meteorological Centre (below) showed the evolution of the surface low.

Given the relatively frequent overpasses of polar-orbiting satellites over the high latitudes, cloud-tracked Atmospheric Motion Vectors (AMVs) can be calculated using Infrared data from VIIRS — examples that combine AMVs from Suomi-NPP and NOAA-20 (source) are shown below.

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CSPP software processes signals at Direct Broadcast antenna sites to create products and imagery with very low latency from Low-Earth Orbit (LEO) satellites. The software includes Microwave Integrated Retrieval System (MIRS) algorithms, including rain rate (available here). How well does that product do in capturing observed precipitation? The toggle above shows GOES-16 Clean Window infrared imagery and derived rain rates (derived from microwave data). The back edge of the precipitation is captured well by the MIRS product, and several heavier bands of precipitation offshore are also suggested. This product is especially useful in the absence of any radar.

How does the rain rate compare to the radar at the same time? The image below (from the College of DuPage website) shows Mosaic Reflectivity at 1750 UTC on 13 February. The back edge of the precipitation in the radar shows agreement with the Rain Rate shown in the toggle above (or here).

The side-by-side comparison, below, highlights detected features. The precipitation band circled in purple appears in both Rain Rate and Radar imagery. The heavier precipitation regions to the east, highlighted by the blue arrows, does not appear in the radar, and highlights an advantage of MIRS Rain Rate: it provides information where radar data are not available.

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