Microwave-derived estimates of Total Precipitable Water (TPW), above, from MIMIC TPW, show an increase in moisture around the Samoan Islands to the west of 170^o W. Percent of Normal mappings of blended TPW in this region, as shown below (taken from this site), show values at >150% of normal.

In anticipation of heavy rains, the National Weather Service Pacific Region requested a Mesoscale Domain (a complete list of messages is here) centered on Tutuila, the main island of American Samoa, through 1100 UTC on 28 January. An animation of GOES-17 Band 13, below, (every 5 minutes, rather than the 1-minute cadence of Mesoscale domains) overlain on top of the Level 2 Total Precipitable Water product (a product that is computed hourly for the Full Disk domain), shows a focus of convection moving westward over American Samoa and Samoa. Note the degradation of the Level 2 Product TPW that is associated with the poor functionality of the Loop Heat Pipe on GOES-17 that occurs at night. Magenta values in the TPW enhancement signify values exceeding 2″. Samoa and American Samoa are within a ribbon of exceptional moisture.

GOES-17 Visible Imagery, below, during the daytime, also show widespread convection moving into the Samoan waters. A benefit of the visible imagery is that surface lines of convergence that may initiate convection are apparent with the 5-minute cadence shown below; those lines are even more apparent in 1-minute imagery (shown here from 1825 – 2234 UTC)

Added, 28 January: the two final hours of the mesoscale domain are shown below. The axis of the deepest moisture has shifted westward through the mesoscale domain from the previous day; showers continue to develop.

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US Space Force EWS-G1 Infrared Window (10.7 µm) images [click to play animated GIF | MP4]

US Space Force EWS-G1 (formerly GOES-13) Infrared Window (10.7 µm) images (above) showed Cyclone Batsirai in the South Indian Ocean as it rapidly intensified from a Tropical Storm at 06 UTC to Category 2 storm (at 12 UTC on 27 January) and briefly exhibited a pinhole eye — and then rapidly collapsed back to Tropical Storm intensity by 00 UTC on 28 January 2022 (SATCON).

EWS-G1 Visible (0.63 µm) images  (below) also displayed the rapid formation of a pinhole eye.

US Space Force EWS-G1 Visible (0.63 µm) images [click to play animated GIF | MP4]

A map of Sea Surface Temperature from the CIMSS Tropical Cyclones site (below) showed that Batsirai had been moving over relatively warm water during its period of rapid intensification. 

Sea Surface Temperature, with the track of Cyclone Batsirai [click to enlarge]

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GOES-16 True Color RGB mages [click to play animated GIF | MP4]

GOES-16 (GOES-East) True Color RGB images created using Geo2Grid (above) displayed the areal extent of snow cover across parts of North Carolina, Virginia, Maryland and Delaware — resulting from a 21-22 January winter storm (NWS Newport/Morehead City NC | NWS Wakefield VA) — that still remained on 24 January 2022.

A Suomi-NPP VIIRS True Color RGB image along with the corresponding GOES-16 Land Surface Temperature (LST) derived product at 1800 UTC or Noon EDT  (below) showed that LST values over deeper snow cover near the Virginia/North Carolina border were held to the upper 30s and low 40s F (shades of blue), in contrast to upper 50s and low 60s F (shades of orange) over bare ground not far to the south and west. The closest reporting station to the coldest LST value of 37ºF was Elizabeth City, NC (where the morning snow depth was 3.0 inches).

Suomi-NPP VIIRS True Color RGB image and GOES-16 Land Surface Temperature product [click to enlarge]

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In addition to its use in detecting wind fields over water (link 1, link 2), SAR data can also be used to detect ice. An example is shown above: similar domains on 20 and 24 January 2022 (from this website; this image on 20 January 2022 and this on one 24 January 2022) are toggled. There is a general increase in Lake Michigan shore ice off shore of southwestern Lower Michigan. Ice concentrations have also increased in western Lake Erie, Lake St Clair, Saginaw Bay in Lake Huron, and along the southwestern shore of Lake Huron. Strong winds were occurring over Lake Huron on the 20th as denoted by the yellow enhancement over the Lake.

SAR data are best used by viewing them each day. The imagery below shows views on different days in December 2021 and January 2022 over Lakes Erie (below) and Michigan (bottom). Note how ice cover can diminish (for example, over Saginaw Bay between 16 and 20 January) in response (typically) to strong winds that can move ice to the middle of the lake where it will melt.

A similar occurrence is shown in Lake Michigan (bottom): there is a filament of near-shore ice on 21 January that had detached from the shoreline under strong southwesterly flow. On 1200 UTC on 22 January, when strong southwesterlies continued, the ice is gone. It’s also not present on 1208 UTC on 23 January, when winds shift back to northerly. Detachment of ice from the shore can be a hazard to fishermen! The Lake Michigan cases also include very strong southwesterly winds (denoted by the yellow enhancements).

Note that ice in a cloud can also cause strong returns that can be misinterpreted as strong winds. Ice will strongly reflect the microwave signals from the RCM (RADARSat Constellation Mission) satellites. That’s the case in this image over Lake Ontario, and this summertime convection view of Lake Superior. Use caution when you see very strong winds; ask: could this be ice in the cloud, or in the lake?

GOES-16 Visible imagery, below, from 21 January 2022 (more imagery from this date is available here), shows challenges in monitoring ice in single-banded imagery. The detached shoreline ice noted in the SAR imagery becomes more faint with time, suggesting melting. The ice over southern Lake Michigan is apparent. Clouds over western Lake Erie make it very hard to interpret ice coverage there.

Very cold air is forecast to overspread the Great Lakes this week. Check to see if ice coverage increases at this link!

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