In spite of a brief downgrade, Sandy maintains hurricane intensity

October 27th, 2012
POES AVHRR 12.0 µm, MODIS 11.0 µm, and Suomi NPP VIIRS 11.45 µm IR images

POES AVHRR 12.0 µm, MODIS 11.0 µm, and Suomi NPP VIIRS 11.45 µm IR images

During the overnight hours after midnight on 27 October 2012, Sandy was briefly downgraded to a Tropical Storm by the National Hurricane Center (discussion archive). A sequence of AWIPS images of 1-km resolution POES AVHRR 12.0 µm, MODIS 11.0 µm, and Suomi NPP VIIRS 11.45 µm IR images (above) showed persistent pockets of deep convection north and west of the center of the tropical cyclone.

Since the Moon was in the waxing gibbous phase (at 97% of full moon phase), it provided ample illumination for a “night-time visible” image using the Suomi NPP Day/Night Band (DNB) at 06:43 UTC or 2:43 AM local time (below). A few overshooting top features could be seen in the DNB image, which corresponded with the areas of colder cloud top IR brightness temperatures seen on the VIIRS 11.45 µm IR image at that same time.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images

After sunrise, GOES-14 1-minute interval SRSOR visible channel data (below; click image to play HD format QuickTime movie) showed great details of the deep convective development north and west of the partially-exposed low-level circulation center.

GOES-14 0.63 µm visible channel image (click image to play QuickTime movie)

GOES-14 0.63 µm visible channel image (click image to play QuickTime movie)

Additional GOES-14 SRSOR images during the afternoon hours (below; cick image to play HD format QuickTime movie) continued to show the development of convective bursts just north of the partialy-exposed low-level circulation center.

GOES-14 0.63 µm visible channel images (click image to play QuickTime movie)

GOES-14 0.63 µm visible channel images (click image to play QuickTime movie)

A larger-scale view using MODIS 0.65 µm visible, 11.0 µm IR, and 6.7 µm water vapor channel images (below) showed the very large size of the cloud field associated with Sandy (which had re-gained hurricane intensity by this time). Also evident on the MODIS water vapor channel image was the large intrusion of dry air wrapping around the southern and eastern quadrants of Sandy, hinting at the early stages of a transition from a tropical system to an extratropical system.

MODIS 0.65 µm visible, 11.0 µm IR, and 6.7 µm water vapor channel images

MODIS 0.65 µm visible, 11.0 µm IR, and 6.7 µm water vapor channel images

An Aqua MODIS true-color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below) revealed large areas of increased turbidity in the waters just west of Florida and the Bahamas, due to mixing from the strond winds associated with Hurricane Sandy.

MODIS true-color Red/Green/Blue (RGB) image

MODIS true-color Red/Green/Blue (RGB) image

Finally, it was observed that there were a number of pilot reports of moderate to severe turbulence near the western periphery of the cloud shield of Sandy, where there were also hints of a transvese banding structure. Two notable pilot reports are displayed on Suomi NPP VIIRS 11.45 µm IR and MODIS 6.7 µm water vapor channel images (below).

Suomi NPP VIIRS 11.45 µm IR image with pilot report of severe turbulence

Suomi NPP VIIRS 11.45 µm IR image with pilot report of severe turbulence

MODIS 6.7 µm water vapor channel image with pilot report of moderate turbuence

MODIS 6.7 µm water vapor channel image with pilot report of moderate turbuence

Hurricane Sandy moves north of the Bahamas

October 26th, 2012
GOES-14 0.63 µm visible channel images and 10.7 µm infrared channel images (click image to play animation)

GOES-14 0.63 µm visible channel images and 10.7 µm infrared channel images (click image to play animation)

SRSO-R operations continue today with GOES-14, allowing for very high temporal resolution imaging of a sheared Hurricane Sandy as it moves away from the Bahamas. The exposed low-level circulation is apparent in the imagery, as well as strong convection north and west of the low-level center. A closer view of the exposed low-level circulation can be seen in this QuickTime movie of GOES-14 visible imagery.

A map of deep layer wind shear, below, from the CIMSS Tropical Cyclones site, shows strong shear associated with an upper level low pressure system south and west of Sandy.

Wind Shear, 1800 UTC 26 October

Wind Shear, 1800 UTC 26 October

A comparison of AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel data (below) showed the exposed low-level circulation center of Sandy at 18:26 UTC (2:26 PM local time), and the deep convection to the north which exhibited cloud top IR brightness temperatures as cold as -87 C (violet color enhancement).

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

GOES-14 Super Rapid Scan Operations (SRSO) Images of Hurricane Sandy

October 25th, 2012
GOES-14 0.63 µm visible channel images (click image to play animation)

GOES-14 0.63 µm visible channel images (click image to play animation)

The GOES-14 satellite was placed into Super Rapid Scan Operations for GOES-R (SRSOR) mode to begin to provide 1-minute interal images of Hurricane Sandy on 25 October 2012. McIDAS images of GOES-14 0.63 µm visible channel data (above; click image to play animation; also available as a QuickTime movie) showed the circulation of Sandy moving northward over the islands of the Bahamas, with the development of a new convective burst in the western semicircle of the storm.

Prior to the initiation of GOES-14 SRSOR, a sequence of AWIPS images of 1-km resolution POES AVHRR 12.0 µm and Suomi NPP VIIRS 11.45 µm IR data (below) showed the circlation of Hurricane Sandy crossing the eastern portion of the island of Cuba.

POES AVHRR 12.0 µm and Suomi NPP VIIRS 11.45 µm IR images

POES AVHRR 12.0 µm and Suomi NPP VIIRS 11.45 µm IR images

A McIDAS-V image of Suomi NPP VIIRS 0.7 µm Day/Night Band data at 05:49 UTC or 1:49 AM local time (below; courtesy of William Straka, CIMSS) offered a “night-time visible” image of Sandy as its center was moving over the southern coast of Cuba.

Suomi NPP VIIRS 0.7 µm Day/Night Band image

Suomi NPP VIIRS 0.7 µm Day/Night Band image

Hurricane Sandy

October 24th, 2012
GOES-13 10.7 µm IR images (click image to play animation)

GOES-13 10.7 µm IR images (click image to play animation)

Hurricane Sandy became the tenth hurricane of the 2012 Atlantic Basin tropical cyclone season on 24 October 2012. McIDAS images of GOES-13 10.7 µm IR data (above; click image to play animation) showed the fairly rapid formation of an eye as the storm approached the eastern portion of the island of Jamaica.

A 15:21 UTC TRMM Microwave Imager (TMI) 85 GHz brightness temperature image from the CIMSS Tropical Cyclones site (below) suggested that a closed eyewall was nearly formed complete by that time.

TRMM Microwave Imagery (TMI) 85 GHz brightness temperature image

TRMM Microwave Imagery (TMI) 85 GHz brightness temperature image

A comparison of AWIPS images of 1-km resolution POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel data (below) showed the eye region of Hurricane Sandy after the center of the storm was passing over Jamaica.

POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel images

POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel images