What appeared to be a rather unusual example of a subtropical cyclone was evident over the northern East Pacific Ocean on 01 November (AWIPS surface analysis + buoys) — however, this compact cyclone was likely associated with a deep cold-core cutoff low that had been over that region for a few days (HPC 500 hPa analyses). GOES-11 IR cloud drift winds (above) showed the broad cyclonic flow around the periphery of the surface low (closer view of AWIPS low-level winds | AWIPS upper-level winds). GOES-11 visible channel imagery (QuickTime animation) showed a cloud structure that almost resembled the eye of a tropical cyclone.

A similar signature was also seen on the GOES-11 10.7µm IR window channel imagery (below), with a ring-like feature of cold cloud top temperatures (-50 to -55 C, yellow to orange enhancement) that was very persistent for much of the day (QuickTime animation). Additional satellite imagery can be found by selecting the Central Pacific 91C.INVEST link at the NRL Tropical Cyclones site.

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A strong cyclone centered over the northcentral US was producing heavy snow across much of North Dakota on 30 October; an associated cold frontal boundary was moving rapidly southward across Nebraska, Colorado, and Kansas during the morning and afternoon hours. The southward push of the cold air behind the front can be seen on an animation of GOES imagery from AWIPS (above), evident as an area of lighter gray enhancement on the 10.7 µm IR window and 3.9µm shortwave IR images (above, upper left and lower left panels) — the leading edge of this cold air was well south of the low cloud deck that was covering parts of South Dakota and northern Nebraska.

In addition, if you look closely, you can also see a subtle reflection of this surface-based boundary moving southward across northeastern Colorado on the 6.5µm “water vapor channel” imagery (above, lower right panel), even though this is a channel which normally senses radiation from altitudes higher in the middle troposphere. A plot of the GOES-12 imager water vapor channel’s weighting function at North Platte, Nebraska (below) indicates that the altitude of the peak contribution for that particular air mass had indeed shifted downward to near 500 hPa (~ 18,000 feet in altitude).

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An early season winter storm dumped up to 25 inches of snow across parts of Colorado on 26 October (NWS snowfall reports); as fate would have it, on that particular day Alaska also reported its first below zero temperature of the season (-7ËšF at Bettles), making for two ominous signs that winter is fast approaching. Aqua MODIS imagery from one day after the storm (above) shows the extent of the resulting snow cover, both in the mountains and also in the eastern Plains of the state; the false-color composite using MODIS channels 2 and 7 (above, right) displays the snow cover as dark red features on the image. Note how the snow cover is distributed both north and south of the Palmer Divide (a west-to-east oriented ridge of higher terrain across eastern Colorado) — upslope flow played an important role in focusing heavy snowfall during different stages of the storm.
A closer view of the Denver area using a MODIS 500-meter resolution true color image (below) shows that many of the small lakes are still unfrozen, and stand out against the surrounding snow covered land surfaces.

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The large (40,000 acre or 63 square mile)  “Esperanza wildfire” started during the early morning hours on 26 October 2006 in a portion of the San Bernardino National Forest near Banning, California (west of Palm Springs); this fire quickly burned out of control, and was responsible for the deaths of 5 firefighters. Santa Ana winds across the region were creating favorable conditions for rapid fire growth (the dew point at nearby Palm Springs dropped from 55ËšF at 19 UTC on 25 October to -1ËšF at 07 UTC on 26 October). GOES-11 3.9µm IR imagery (QuickTime animation, above) showed very hot brightness temperatures (yellow to red enhancement) in the vicinity of this large fire — hot fire pixels were first evident at 08:15 UTC (01:15 AM local time), and image pixel values reached the saturation temperature of the GOES-11 3.9µm detectors (337.2ËšK / 64ËšC / 147ËšF) as early as 12:45 UTC (5:45 AM local time). The Wildfire ABBA product (GOES-11 | GOES-12) also indicated saturated fire pixels (yellow) in that area (20:45 UTC WF_ABBA image).

GOES-11 visible channel imagery (QuickTime animation, below) showed a very large smoke plume from this fire, which was dispersed in different directions due to directional wind shear between the surface and the 500 hPa level (~18,000 feet in altitude). MODIS imagery of the fire from 26 October is posted on the UMBC Air Quality Smog Blog, while the IDEA Aerosol Optical Depth product from the following day shows continued smoke transport out across the adjacent Pacific Ocean.

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