GOES-11 6.7µm “water vapor channel” imagery (above; QuickTime animation) revealed a textbook signature of an occluding cyclone over the Gulf of Alaska on 17 May 2007. A dry slot begins to interact with a baroclinic leaf feature after 00:00 UTC, with a distinct cloud head or “comma head” forming after 06:00 UTC. After 12:00 UTC, the characteristic “dry swirl” pattern is evident on the water vapor imagery, indicating that the cyclone was entering the occluded phase of its life cycle.

A classic hook-shaped pattern was also seen on AWIPS imagery of the DMSP SSM/I rainfall rate product (below), although rainfall rates were fairly light (in the 1-2 mm per hour range). NOAA Ocean Prediction Center guidance was forecasting gale and storm force winds in the northwestern quadrant of the occluding cyclone.

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A cross section oriented west to east through the cyclone at 18:00 UTC using AWIPS GFS90 model fields indicated that the dynamic tropopause (taken to be 1.5 Potential Vorticity Units, purple to blue enhancement, above) was fairly low across the region of the cyclone (below the 500 hPa pressure level), with a hint of stratospheric air (greater than 1.5 PVU) extending downward to near the surface. A corresponding cross section of Relative Humidity (below) showed the very dry air (RH values less than 20%, orange to red enhancement) associated with the elevated dry slot that was wrapping around the cyclone.

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GOES-12 3.9µm InfraRed (IR) imagery (above; Java animation) showed a large “hot spot” associated with a wildfire in New Jersey — this fire was apparently started by a flare from a military F-16 fighter jet on a routine training exercise (CNN article), which ignited the dry shrub and oak pine in that area during the afternoon of 15 May 2007. In less than 90 minutes this fire became hot enough to saturate the GOES-12 3.9µm detectors, causing the brightness temperatures to “roll over” and be displayed as a very “cold” pixels (white enhancement) — the GOES-12 Wildfire ABBA product at 21:15 UTC (below) indicated a large area of yellow-colored saturated fire pixels.

A smoke plume was seen on GOES-12 visible channel imagery (below; Java animation), drifting eastward over the adjacent offshore waters of the Atlantic Ocean. This smoke plume was also detected on radar. As of 16 May, this fire had burned over 13,000 acres, damaging about a dozen homes and causing thousands of residents to evacuate.

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GOES-12 visible imagery from 11 May 2007 (above; Java animation) shows the very thick areas of smoke resulting from ongoing fire activity in Georgia and Florida. Strong winds around the periphery of the remnants of Subtropical Storm Andrea continued to create an environment favorable for fire growth. A few convective bursts near the center of the tropical depression were evident during the day, but the convection remained disorganized and weak.

The highest concentration of smoke (MODIS true color image) was within a west-to-east oriented zone of diffluence where winds were generally weaker (across the eastern Gulf of Mexico and southern Florida). This smoke remained in that general region on the following day (12 May), and IDEA trajectories (below) indicated that a slow transport of this thick smoke would continue to gradually disperse it during the subsequent 24-48 hour period.

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AWIPS images of the GOES-12 6.5µm “water vapor channel” (above; QuickTime animation) revealed the large size of a cyclonic circulation off the southeast US coast on 08 May 2007. This system was eventually named Subtropical Storm Andrea by the National Hurricane Center the following morning. One noteworthy aspect of Andrea was the fact that it’s formation ended the longest period recorded in the satellite era (33 days) without a tropical cyclone in any ocean basin (the last tropical cyclone was Tropical Cyclone Cliff in the South Pacific Ocean, which dissipated on 06 April 2007).

GOES-12 water vapor winds (above) showed several upper-tropospheric targets of 50 knots (57 mph) or greater in the northern quadrant of the cyclone at 15:00 UTC on 08 May — Buoy 41013 off the coast of North Carolina reported a wind gust of 48 knots (55 mph) earlier that day. The strong winds around the periphery of the storm were causing ongoing wildfires in Georgia and Florida to intensify, creating very impressive smoke plumes which drifted southward across parts of Florida and the adjacent offshore waters of the Gulf of Mexico (GOES-12 visible images: Java animation). Thick smoke (which caused air quality problems and highway closures in some areas of Florida) was also very evident on MODIS true color imagery (below) and on the MODIS Aerosol Optical Depth (AOD) product.

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