Hurricane Kenneth

November 20th, 2011 |
GOES-11 0.65 µm visible channel images + ship reports

GOES-11 0.65 µm visible channel images + ship reports

According to the National Hurricane Center, on 20 November 2011 Tropical Storm Kenneth became the latest-forming named tropical storm in the eastern North Pacific basin since Hurricane Winnie formed on 04 December 1983. GOES-11 0.65 µm visible channel images from the CIMSS Tropical Cyclones site (above) showed a well-defined circulation, with a ship report of tropical storm force winds north of the storm center.

The corresponding GOES-11 10.7 µm IR images (below) showed a trend of increasing convection withing the northern semicircle of the storm.

GOES-11 10.7 µm IR images + ship reports

GOES-11 10.7 µm IR images + ship reports

AWIPS images of the MIMIC Total Precipitable Water (TPW) product (below; click image to play animation) indicated that TPW values associated with Tropical Storm Kenneth were in the 50-60 mm range (darker orange colors), as rich moisture was sill in place along the Inter-Tropical Convergence Zone (ITCZ) / Monsoon Trough.

MIMIC Total Precipitable Water (TPW) product (click image to play animation)

MIMIC Total Precipitable Water (TPW) product (click image to play animation)

======== 21 November Update ========

GOES-15 0.63 µm visible images (click image to play animation)

GOES-15 0.63 µm visible images (click image to play animation)

Kenneth was upgraded to a Hurricane on 21 November. GOES-15 0.63 µm visible channel images (above; click image to play animation) showed a ragged eye forming as curved convective bands wrapped around the center of the tropical cyclone. Kenneth was able to intensify in part because it was in an environment that possessed uncharacteristically low values of deep layer wind shear (below).

GOES-11 10.7 µm IR image + deep layer wind shear

GOES-11 10.7 µm IR image + deep layer wind shear

======== 22 November Update ========

GOES-15 0.63 µm visible channel images (click image to play animation)

GOES-15 0.63 µm visible channel images (click image to play animation)

Hurricane Kenneth strengthened to a Category 4 storm on 22 November, becoming the most intense major hurricane to form so late in the season in the satellite era. GOES-15 0.63 µm visible channel images (above; click image to play animation) showed the well-defined eye of Kenneth.

Mountain waves over Colorado and New Mexico

November 12th, 2011 |
GOES-11, GOES-13, GOES-15, and MODIS water vapor channel images

GOES-11, GOES-13, GOES-15, and MODIS water vapor channel images

A comparison of 8-km resolution GOES-11 6.7 µm water vapor channel, 4-km resolution GOES-13 and GOES-15 6.5 µm water vapor channel, and 1-km resolution Aqua MODIS 6.7 µm water vapor channel images (above) demonstrated how differences in satellite viewing angle as well as differences in satellite sensor spatial resolution have an impact in being able to resolve the structure and areal coverage of small-scale features such as the mountain waves that existed across much of southeastern Colorado and northeastern New Mexico around 19:45 UTC on 12 November 2011.

There were a number of pilot reports of moderate to severe turbulence aloft across the region – and at the surface, wind gusts as high as 115 mph were reported. As can be seen in a comparison of 1-km resolution MODIS 0.65 µm visible channel and MODIS 6.7 µm water vapor channel images (below), many of the mountain waves were located in cloud-free areas — this highlights the value of water vapor channel imagery for identifying such regions of potential aircraft turbulence.

MODIS 0.65 µm visible channel + MODIS 6.7 µm water vapor channel images

MODIS 0.65 µm visible channel + MODIS 6.7 µm water vapor channel images

Intense Bering Sea Extratropical Cyclone

November 9th, 2011 |
MTSAT-1R 6.7 µm water vapor channel images

MTSAT-1R 6.7 µm water vapor channel images

McIDAS images of MTSAT-1R 6.7 µm water vapor channel data (above) showed an intense extratropical cyclone that was moving toward the Bering Sea region during the 07 November – 08 November 2011 time frame. Of particular interest was the presence of a very warm/dry (dark black) circular region within the dry slot sector of the developing cyclone, which could have been associated with a strong potential vorticity anomaly.

A color-enhanced comparison of MTSAT-1R and GOES-11 6.7 µm water vapor channel data (below; click image to play animation) demonstrated the difference that satellite viewing angle (MTSAT looking from the west; GOES-11 looking from the east) and satellite sensor spatial resolution (the MTSAT-1R water vapor channel is “4 km” at nadir, while the GOES-11 water vapor channel is “8 km” at nadir) play in the ability to resolve such potentially important dynamical features. The core of the aforementioned MTSAT-1R dry feature moved directly over Shemya Island around 12:00 UTC on 08 November (MODIS IR image with surface analysis), where a surface wind gust of 83 mph was recorded at Shemya Air Force Base. Then, once the storm began to move northward over the Bering Sea, a more “curved banding” structure was seen on water vapor imagery as the cyclone began to wrap filaments of dry air around the deepening storm center. Although the sun angle was low, some of the “banding structure” could be seen in GOES-11 0.65 µm visible channel images.

MTSAT-1R (left) and GOES-11 (right) 6.7 µm water vapor channel images (click image to play animation)

MTSAT-1R (left) and GOES-11 (right) 6.7 µm water vapor channel images (click image to play animation)

While the dry slot features began to lose their definition in the geostationary MTSAT-1R and GOES-11 water vapor images (in part due to the upward shift in the peak of the water vapor channel weighting function with increasing satellite viewing angle), a direct overpass of the Aqua satellite around 23:45 UTC on 08 November provided a nice view using the 6.7 µm water vapor channel on the MODIS instrument (below). Using the MODIS imagery, good dry slot structure could be seen, even after the storm had moved northward over the Bering Sea.

Aqua MODIS 6.7 µm water vapor channel image

Aqua MODIS 6.7 µm water vapor channel image

A sequence of AWIPS images of 1-km resolution MODIS 11.0 µm and POES AVHRR 12.0 µm InfraRed data (below; click image to play animation) showed the storm at various phases as it was rapidly deeping during its northward trek over the Bering Sea.

MODIS 11.0 µm and POES AVHRR 12.0 µm InfraRed images (click image to play animation)

MODIS 11.0 µm and POES AVHRR 12.0 µm InfraRed images (click image to play animation)

This ended up being one of the strongest Bering Sea storms on record — the winds exceeded hurricane force across a very expansive area, producing high seas and major coastal flooding and beach erosion along parts of western Alaska. At the Tin City Airways Facility Sector (located near the western tip of the Seward Peninsula), they reported sustained winds of 72 mph with gusts to 85 mph — and the minimum altimeter air pressure was 28.46 inches. A peak gust of 89 mph was reported nearby at Wales. As the storm moved over St, Lawrence Island, minimum altimeter air pressure readings were 28.21 inches and 28.28 inches at Gambell and Savoonga, respectively.

The entire evolution of the storm during the 08-09 November time period can be seen on an animation of 15-minute interval GOES-11 10.7 µm IR images (below; click image to play animation).

15-minute interval GOES-11 10.7 µm IR images (click image to play animation)

15-minute interval GOES-11 10.7 µm IR images (click image to play animation)

Augmented Scanning Schedule for GOES-West

November 4th, 2011 |
GOES-15 10.7-micrometer image at new 'sub-CONUS' scale

GOES-15 10.7-micrometer image at new 'sub-CONUS' scale

A new scanning schedule that adds more sectors is being followed for GOES-15 as the satellite drifts westward towards 135 W. When GOES-15 becomes the new GOES-West, replacing GOES-11 (planned to occur on December 6th), the augmented scanning schedule will become operational, offering 1 or 2 additional scans per hour of the Continental United States (at the so-called ‘sub-conus scale’ depicted here). There images scans start at 11 and 41 minutes past each hour (except when full-disks are taken every three hours, in which case only the image at 41 minutes past the hour is produced). Visible image sizes are 2400×4800 pixels; infrared images sizes are 600×1200.

This image shows the current operational GOES-West imager scanning schedule. Here is the augmented schedule. Note the addition of small images just before the nn:15 and nn:45 images. Because GOES-15 is moving, the geographic coverage for the sub-CONUS imagery is not yet where it will be when GOES-15 is on station at 135 W Longitude.

Recall that GOES-15 has improved water vapor imagery resolution over GOES-11. (Link). In addition, the 12-micrometer channel on GOES-11 will be replaced by a 13.3 micrometer channel on GOES-15. In addition, the visible channel will subtly shift to a channel with a narrower response with a peak at 0.63 micrometers.