As Hurricane Noel made the transition to an extratropical cyclone during the 02 to 03 November 2007 period, it remained a very large and very powerful storm system that significantly impacted the Atlantic coast regions of the northeastern US and southeastern Canada with hurricane force winds (91 mph at Horseshoe Shoal MA), heavy rain (4.83 inches at Bass Harbor ME), high seas (46.0 foot waves at Buoy 44011), and even heavy snow (6.0 inches at Fort Kent ME). AWIPS images of the GOES-12 6.5 µm “water vapor” channel (above) showed a very pronounced warm/dry band (orange enhancement) just south of the main cloud shield along the southern quadrant of the storm. This particular water vapor signature often indicates a potential for very strong winds at the surface as momentum from aloft is transferred downward into the boundary layer; the southern flank is also a favored area for strong surface winds in an extratropical cyclone.

An AWIPS image of the 6.7 µm MODIS water vapor channel around 02:45 UTC (below) with 03 UTC surface reports reveals that Fixed Buoy 41048 (located west of Bermuda, station ID TXKF) was situated near the leading edge of the water vapor dry band, and experienced a peak wind gust (from the south) of 62 knots near the time of the MODIS image. Buoy 41048 recorded a peak wind gust of 69 mph at 01:50 UTC, and a peak wave height of 37.1 feet at 02:50 UTC.

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Hurricane Noel remained a minimal Category 1 hurricane early in the day on 02 November 2007, although the satellite presentation was starting to deteriorate (GOES-12 IR animation) as the storm began the transition to an extratropical system. SeaWinds scatterometer data from the QuikSCAT satellite around 10:48 UTC (above, and below) did show two wind retrievals of 74 knots just to the northwest of the storm center. However, those two 74 knot wind speed points had the “Rain Flag” active (all the wind barbs with circles on the CIMSS Tropical Cyclones TCTrak display have the Rain Flag active), meaning that the presence of rainfall may have contaminated the data at those points — energy backscattered from large rain drops can constitute a significant (but unknown) portion of the measured echo energy.

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Tropical Storm Noel intensified late in the day on 01 November 2007 to become a minimal Category 1 hurricane just north of the Bahamas. AWIPS images of the GOES-12 10.7µm IR channel (above) show that the circular area of very cold cloud top temperatures (colder than -80º C, green enhancement) became more well-defined and moved closer to the surface circulation during the intensification process.

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After spending some time meandering over Cuba and just off the northern coast of the island, Tropical Storm Noel began to intensify a bit and produce bursts of convection within its eastern semicircle as it started to move slowly northward during the day on 31 October 2007. AWIPS images of the GOES-12 10.7 µm IR channel (above) revealed a significant increase in the areal coverage of very cold cloud top temperatures (below -80ºC, light green enhancement); in fact, isolated IR brightness temperatures as cold as -92º C (white pixels) were noted at 04:01 UTC on 01 November.

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