Atlantic Basin GOES-13 IR images

GOES-13 10.7 µm IR images (above) showed 3 tropical cyclones in the Atlantic Basin on 14 September 2010: from left to right, Tropical Storm Karl, Hurricane Igor, and Hurricane Julia. Real-time visible and IR images covering the Tropical Atlantic are available from NOAA/NESDIS/OSDPD/SSD.

A comparison of geostationary-orbiting satellite IR images and polar-orbiting microwave images (from the CIMSS Tropical Cyclones site) for each of the 3 tropical cyclones are shown below. Note that there is a 1-2 hour difference between the IR images and the microwave images — however, these comparisons show the utility of the microwave images for showing tropical cyclone structures that are often masked by the cold convective cloud shield.

Tropical Storm Karl: geostationary IR image + polar microwave image

Hurricane Igor: geostationary IR image + polar microwave image

Hurricane Julia: geostationary IR image + polar microwave image

An AWIPS image of EUMETSAT METOP Advanced Scatterometer (ASCAT) winds (below) indicated surface winds as high as 63 knots near the center of Hurricane Igor at 13:28 UTC; however, ASCAT winds are known to have a low speed bias (which increases as winds get to higher speeds).

EUMETSAT METOP ASCAT winds

As part of the GOES-15 Post Launch Science Test, the satellite was placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5 minutes during the day. The evolution of the eye of Hurricane Igor is seen on GOES-15 0.63 µm visible channel images (below; also available as a QuickTime movie) — note the occasional presence of small mesovortices within the eye region.

GOES-15 0.63 µm visible channel images

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GOES-15 0.63 µm visible images (Super Rapid Scan Operations)

As part of the GOES-15 Post Launch Science Test, the satellite was placed into Super Rapid Scan Operations (SRSO) mode on 13 September 2010, providing images as frequently as every 1 minute during the day. GOES-15 0.63 µm visible channel images (above; also available as a QuickTime movie) showed the well-defined eye of Hurricane Igor, with SRSO images during a 4 hour period (from 16:39 – 20:39 UTC). The visible images were brightened a bit after 19:26 UTC to help detect the presence of any mesoscale vortices within the eye.

A comparison of 1-minute interval GOES-15 SRSO images with the normal operational 15-minute interval GOES-13 visible images (below) clearly demonstrates the advantage of higher temporal resolution for monitoring the evolution of the eye structure of the hurricane (courtesy of Tim Schmit, NOAA/ASPB).

GOES-15 1-minute visible images (left) and GOES-13 15-minute visible images (right)

While Hurricane Igor maintained a Category 4 intensity for more than 24 hours, an SSMI/S 85 GHz microwave brightness temperature image from the CIMSS Tropical Cyclones site (below) suggested that the storm might be entering an eyewall replacement cycle (ERC) late in the day on 13 September, which would signal a likely decrease of the storm’s intensity during the ERC process.

SSMI/S 85 GHz microwave brightness temperature image

A large eye was also evident on GOES-13 10.7 µm IR imagery (below).

GOES-13 10.7 µm IR images

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SSMI/S 85 GHz microwave brightness temperature image

An SSMI/S 85 GHz microwave brightness temperature image from the CIMSS Tropical Cyclones site (above) displayed a well-defined eyewall structure associated with Hurricane Igor ar 11:32 UTC on 12 September 2010.

GOES-13 1-km resolution 0.63 µm visible channel images (below) showed an improving appearance to the eye of Igor during the morning hours.

GOES-13 0.63 µm visible channel images

========== UPDATE ==========

GOES-13 10.7 µm IR images

Igor rapidly intensified into a Category 4 hurricane later in the day. GOES-13 4-km resolution 10.7 µm IR images (above) displayed a well-defined eye, while a plot of the CIMSS Advanced Dvorak Technique (below) showed the trend of rapid intensification.

Plot of the CIMSS Advanced Dvorak Technique (ADT)

1-km resolution GOES-13 0.63 µm visible channel images (below) showed a fairly nice eye structure during the daytime hours.

GOES-13 0.63 µm visible channel images

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GOES-13 10.7 µm IR images

Hurricane Igor became the 4th hurricane of the season in the Atlantic Basin late in the day on 11 September 2010. GOES-13 10.7 µm IR images from the CIMSS Tropical Cyclones site (above) displayed an increasingly organized structure to the convection surrounding the center of the storm. Igor existed in an environment of low deep layer wind shear, which was a favorable factor for further intensification.

The development of a few convective bursts near the center of Igor’s circulation could be seen on GOES-13 0.63 µm visible images (below), suggesting the formation of an eyewall.

GOES-13 0.63 µm visible images

A 22:56 UTC microwave image from the SSMI/S instrument (below) revealed a well-defined convective ring around the center of Igor.

SSMI/S 85 GHz mircrowave brightness temperature

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