Synthetic Aperture Radar (SAR) data retrievals continue over Guam, with 10 planned for November. The toggle above compares the 2009 UTC SAR footprint (from RADARSAT-2) with Himawari-8 Clean Window (10.41) infrared imagery at 2010 UTC (on 5 November 2022). These data are also available online at this NOAA/STAR Website; there are also direct links to wind analyses and Normalized Radar Cross Section (NRCS) data. MetOp-B Scatterometer winds for this time (from the manati website), show light southeasterly winds over the Guam and islands to its northeast: Rota, the very small Aquipan, Tinian and Saipan.

The SAR Wind observations show several things. Each of the islands has a wind shadow, with lighter winds downwind of the islands (that is, to their north and west given the prevailing southeasterlies). The strongest winds — 30 to 40 knots — are most likely a result of cloud ice causing a much greater SAR return, and this can be verified by viewing the Normalized Radar Cross Section, shown below, from this link. Feathery features that occur in the NRCS imagery are most likely cloud ice, and the enhanced reflection from that cloud ice results in an analysis that shows stronger surface winds than may be present. So an analyst who sees very strong winds in/near deep convection should verify what kind of hydrometeors might be in the cloud.

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SAR Winds just to the west of the island of Saipan show 5 separate strong maxima in a region where Himawari-8 data show little evidence of cloudiness. This image of Saipan from the International Space Station suggests a possible reason: ships at anchor in Saipan’s harbor! Such ships are highly reflective in C-band frequencies as used on RADARSAT-2.

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Thanks to Brandon Aydlett, SOO at WFO Guam, for pointing out the artifacts near Saipan!

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Another RADARSAT-2 pass occurred at 0823 UTC on 7 November. The toggle with Himawari-8 infrared imagery is shown below. Again, weaker winds are shown downwind of the islands (in this case, to the west of the islands as winds have shifted to a more easterly direction; click here to see the wind analysis and the NRCS analysis, both from this website) To the east of Guam are numerous dipoles of strong/weak winds associated with showers.

The toggle below zooms in on the shower activity near 13.5^oN, 147.75^oE, to the east of Guam. Stronger winds (10-15 knots, yellow and brown in the enhancement) are apparent to the east of the cooler clouds that are mostly likely tradewind cumulus showers. The strongest winds, 20+ knots might be associated with ice in clouds. Himawari-8 Band 13 brightness temperatures over the showers are in general not sub-freezing (the exception being the cyan and blue enhancements where brightness temperatures are from -5^o to -8^o C. The small NRCS image underneath the toggle (snipped from here), however, shows some bright feathered regions that suggest ice is present in small (perhaps smaller than the Himawari-8 infrared resolution) regions within the clouds (this image references NRCS features with the zoomed-in SAR wind image shown below)

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Note that the very large signals persist just to the west of Saipan — and there’s one more ship, apparently!

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Fire Temperature RGB, Shortwave Infrared (3.9 µm), Fire Power derived product and Fire Temperature derived product images (above) showed the thermal signatures associated with a wind-driven grassland fire in north-central South Dakota on 06 November 2022. The Fire Temperature and Fire Power derived products are components of the GOES Fire Detection and Characterization Algorithm FDCA. The earliest unambiguous fire signature was seen in the 3.9 µm imagery at 1720 UTC, as infrared brightness temperatures began to increase. The first Fire Power pixel then appeared at 1724 UTC, with the first Fire Temperature RGB pixel appearing at 1727 UTC. At 1743 UTC, the hottest 3.9 µm brightness temperature occurred (9.78ºC) along with the peak Fire Power value of 1459.1 MW.

GOES-16 True Color RGB images from the CSPP GeoSphere site (below) displayed the smoke plume as it drifted southeastward and eventually crossed the South Dakota / Minnesota border — and a dark burn scar became apparent at the fire source region.

NOAA-20 VIIRS True Color and False Color RGB images valid at 1944 UTC (below) provided a higher spatial resolution view of the smoke plume; on the False Color RGB image, pink pixels highlighted the hottest portions of the wind-driven fire at that time. The VIIRS data used to create these images were acquired and processed by the SSEC/CIMSS Direct Broadcast ground station.

===== 07 November Update =====

During the subsequent nighttime hours, a comparison of NOAA-20 VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images valid at 0759 UTC (above) showed the bright glow and warm thermal signature associated with a small remnant fire near the northwestern end of the burn scar — but the small thermal signature was not apparent in lower spatial resolution GOES-16 Shortwave Infrared (3.9 µm) imagery at 0756 UTC.

This small fire was not evident in a later Suomi-NPP VIIRS Day/Night Band image valid at 0852 UTC (below) — but the 7-8 mile long dark burn scar was easily seen between Bowdle and Loyalton.

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1-minute GOES-16 (GOES-East) Mesoscale Domain Sector “Red” Visible (0.64 µm) images (above) included time-matched (+/- 4 minutes) plots of SPC Storm Reports — which showed thunderstorms that moved northeastward across parts of Texas, Oklahoma, Arkansas and Louisiana during the hours leading up to sunset on 04 November 2022.

The corresponding 1-minute GOES-16 “Clean” Infrared Window (10.35 µm) images  (below) continued for several hours past sunset — and indicated that the coldest pulsing overshooting tops exhibited infrared brightness temperatures in the -70 to -75ºC range (interior pixels having a darker black to lighter white enhancement). These storms produced hail up to 2.75 inches in diameter in Texas, and damaging winds up to 108 mph in Oklahoma — along with widespread tornadoes (with some resulting in fatalities). The EF-4 tornado which tracked from Red River County, TX to McCurtain County, OK was the first EF-4 tornado in NWS Shreveport’s County Warning Area since 29 November 2010, and the first Oklahoma EF-4 since 09 May 2016.

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GOES-16 (GOES-East) Mid-Level Water Vapor (6.9 µm) and Air Mass RGB images (above) covered the period 0600-1800 UTC on 03 November 2022 — during which Category 1 Hurricane Martin transitioned to an extratropical cyclone over the North Atlantic Ocean (surface analyses). West of Martin, the large area of orange-to-red hues on the Air Mass RGB images highlighted an anomalously-deep mid-tropospheric trough that was moving eastward (also shown by UKMET model 500 hPa height contours) — which began to phase with and absorb the mid-tropospheric circulation of Martin as the extratropical transition completed.

DMSP-17 SSMIS Microwave (85 GHz) imagery at 1005 UTC (below) — from the CIMSS Tropical Cyclones site — indicated that a closed eyewall was not present with Martin at that time.

VIIRS True Color RGB and Infrared Window (11.45 µm) images from Suomi-NPP (at 1447 UTC) and NOAA-20 (at 1537 UTC) viewed using RealEarth (below) showed Martin around the time that extratropical transition was nearly complete.

GOES-16 Nighttime Microphysics RGB and daytime True Color RGB images from the CSPP GeoSphere site (below) displayed the center of Martin moving rapidly north-northeastward (at speeds of 40-50 knots) during the day.

Additional imagery of Martin can be seen in this blog post.

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