A better view of the offshore ice (as well as the ice in central Hudson Bay, northeast of the aforementioned mesoscale low) was provided by Suomi NPP VIIRS true-color and false-color images, visulized using the SSEC RealEarth web map server (below). In the false-color image, snow cover and ice appear as darker shades of cyan.A comparison of Canadian Ice Service analyses from 16 November and 23 November (below) showed the growth of the offshore ice along the western and northwestern edges of Hudson Bay, as well as the larger area of ice growing southward in the central portion of Hudson Bay during that 1-week period. The departure from normal images at the bottom indicated that ice concentration along the western and northwestern edges was well below normal (red), while the concentration of the large area of ice in central Hudson Bay was greater than normal (blue).
The corresponding 4-km resolution GOES-15 Infrared (10.7 µm) images (below) revealed that cloud-top IR brightness temperatures quickly cooled from -23º C at 2130 UTC to -42º C at 2200 UTC.There was a 30-minute gap in GOES-15 coverage from 2100 to 2130 UTC (due to a full disk scan), but a comparison of 1-km resolution NOAA-19 AVHRR Visible (0.63 µm) and Infrared (10.8 µm) caught the very early growth of the tornado-producing storm at 2115 UTC (below). The cloud-top IR brightness temperatures were as cold as -23º C at that time, indicating a high probability that cloud glaciation had begun. A timely overpass of the Suomi NPP satellite allowed a comparison of 375-meter resolution VIIRS Visible (0.64 µm) and Infrared (11.45 µm) images during the time that the tornado was srill on the ground (below). Once again, the strong slant of the storms due to increasing wind speeds aloft allowed the western/southwestern sides of the thunderstorm clouds to be brightly illuminated on the visible image. The coldest cloud-top IR brightness temperature was -51º C (yellow color enhancement), which was just shy of the -53º C tropopause temperature reported on the Oakland rawinsonde report at 12 UTC. A VIIRS true-color image of the storm visualized using RealEarth is shown below. The actual satellite overpass time was around 2151 UTC. GOES-15 sounder Lifted Index (LI) derived product images (below) showed the pockets of post-frontal instability over central California — LI values less than -4 C were seen (yellow color enhancement).
GOES-13 Visible Imagery, above, shows Tropical Storm Kate northeast of the Bahamas late in the day on 9 November. The storm is over a region of warm sea surface temperatures, below (imagery from the CIMSS Tropical Weather Site), in an environment of low shear. RapidScat winds show winds between 35 and 40 knots to the northeast of the storm center. The projected path is also shown, paralleling the East Coast before moving out to sea. The path takes the storm north of Bermuda as well.
Suomi NPP viewed the storm as well, shortly after noon on 9 November. The Visible (0.64 µm), near-infrared (1.61 µm) and 11.35 µm imagery are shown below. The 1.61 imagery shows darker returns over ice clouds because of absorption at that wavelength. The extensive cirrus shield over Kate’s convection (and along the East Coast is association with frontal system) is readily apparent. Water-based clouds, in contrast, are bright white in both the visible and near-infrared channels.
ASCAT winds from 0230 UTC on 10 November (below) also show strongest winds on the northern and eastern sides of the storm.
Kate was upgraded to a minimal Hurricane at 0900 UTC on 11 November.