GOES-17 Water Vapor imagery sensing the surface in northern Alaska

January 18th, 2019 |
GOES-17 Low-level Water Vapor (7.3 µm) images, plus topography [click to play animation | MP4]

GOES-17 Low-level Water Vapor (7.3 µm) images, plus topography [click to play animation | MP4]

* GOES-17 images shown here are preliminary and non-operational *

A comparison of GOES-17 Low-level Water Vapor (7.3 µm) images with topography (above) revealed that radiation being emitted by the higher elevations of the Brooks Range in northern Alaska was able to be sensed by the 7.3 µm detectors — in spite of the very large satellite viewing angle (or zenith angle) around 75 degrees.

The GOES-17 ABI Water Vapor band weighting functions calculated using 12 UTC rawinsonde data from Fairbanks (below) showed that the presence of cold, dry air within the middle to upper troposphere had shifted the peak pressure of the 7.3 µm band downward to 753.63 hPa (corresponding to an altitude of 7053 feet) — which was at or below the elevation of much of the higher terrain of the Brooks Range. There was very little absorption of upwelling surface radiation by the small amount of water vapor that was present within the middle/upper troposphere, allowing the thermal signature of the terrain to be observed on the Water Vapor imagery.

GOES-17 Water Vapor weighting functions calculated using 12 UTC rawinsonde data from Fairbanks [click to enlarge]

GOES-17 Water Vapor weighting functions calculated using 12 UTC rawinsonde data from Fairbanks [click to enlarge]

Rope cloud in the East Pacific Ocean

January 16th, 2019 |
GOES-17

GOES-17 “Red” Visible (0.64 µm) image, with an overlay of the 12 UTC surface analysis [click to enlarge]

* GOES-17 images shown here are preliminary and non-operational *

An 1802 UTC GOES-17 “Red” Visible (0.64 µm) image with an overlay of the 12 UTC surface analysis (above) revealed a well-defined rope cloud which stretched for nearly 1000 miles, marking the cold front position at the time of the image. Rope clouds can therefore be used to diagnose the exact location of the leading edge of a cold frontal boundary between times when surface analyses are available. In this case, the cold front was associated with a Hurricane Force low over the East Pacific Ocean on 16 January 2019 (surface analyses).

GOES-17 "Red" Visible (0.64 µm) images [click to play animation]

GOES-17 “Red” Visible (0.64 µm) images [click to play animation]

An animation of GOES-17 Visible images is shown above, with a zoomed-in version closer to the rope cloud displayed below.

GOES-17 "Red" Visible (0.64 µm) images [click to play animation]

GOES-17 “Red” Visible (0.64 µm) images [click to play animation]

An even closer look (below) showed that the rope cloud was only about 2-3 miles wide.

GOES-17 "Red" Visible (0.64 µm) images [click to enlarge]

GOES-17 “Red” Visible (0.64 µm) images [click to enlarge]

When the 18 UTC surface analysis later became available, a close-up comparison with the 1802 UTC GOES-17 Visible image (below) indicated that the northern portion of the cold front (as indicated by the rope cloud) was slightly ahead of — and the southern portion slightly behind — the smoothed cold frontal position of the surface analysis product.

1802 UTC GOES-17 "Red" Visible (0.64 µm) image, with an overlay of the 18 UTC surface analysis [click to enlarge]

1802 UTC GOES-17 “Red” Visible (0.64 µm) image, with an overlay of the 18 UTC surface analysis [click to enlarge]

NOAA-15 AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images at 1617 UTC [click to enlarge]

NOAA-15 AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images at 1617 UTC [click to enlarge]

1-km resolution AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images of the rope cloud were captured by NOAA-15 at 1617 UTC (above) and by NOAA-18 at 1710 UTC (below). Along the northeastern portion of the rope cloud, there were a few convective clouds which exhibited cloud-top infrared brightness temperatures as cold as -55 to -60ºC (darker shades of red) and were tall enough to be casting shadows due to the low morning sun angle.

NOAA-18 AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images [click to enlarge]

NOAA-18 AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images at 1710 UTC [click to enlarge]


===== 17 January Update =====

GOES-17 True Color RGB images [click to play animation | MP4]

GOES-17 True Color RGB images [click to play animation | MP4]

On the following day, another rope cloud (one that was more fractured) was seen moving across Hawai’i as a cold front passed the island of Kaua’i — the southeastward progression of the rope cloud was evident on GOES-17 True Color Red-Green-Blue (RGB) images (above)  from the UW AOS site.

Surface observations plotted on GOES-17 Visible images (below) showed the wind shift from southwest to north as the cold front moved through Lihue on Kauwa’i around 00 UTC.

GOES-17

GOES-17 “Red” Visible (0.64 µm) images, with plots of surface reports [click to play animation | MP4]

===== 18 January Update =====

Suomi NPP VIIRS Day/Night Band (0.7 µm) image, with and without buoy observations [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image, with and without buoy observations [click to enlarge]

Not all rope clouds are associated with cold fronts; with ample illumination from the Moon — in the Waxing Gibbous phase, at 90% of Full — a Suomi NPP VIIRS Day/Night Band (0.7 µm) image (above) provided a “visible image at night” of a rope cloud in the northern Gulf of Mexico which highlighted a surface wind shift axis.

A sequence of VIIRS Day/Night Band images from NOAA-20 and Suomi NPP (below) showed the movement of the rope cloud during a time span of about 1.5 hours.

NOAA-20 and Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

NOAA-20 and Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

Stereoscopic views of a small storm over the North Pacific Ocean

January 16th, 2019 |

Himawari-8 AHI and GOES-17 ABI Band 13 (10.41 µm and 10.35 µm, respectively) at 0400 UTC on 16 January 2019 (Click to enlarge)


GOES-17 Data in this post are preliminary and non-operational.

The toggle above shows clean window imagery from the Advanced Himawari Imager (Band 13, 10.41 µm) on Himawari-8 (data courtesy JMA) and clean window imagery from the Advanced Baseline Imager (ABI, Band 13, 10.3 µm) on GOES-17 (GOES-17 data are non-operational). There is a small developing storm between the Hawai’ian Islands and Alaska that is resolved by both satellites.  The storm is in between the two satellites and therefore ideal for stereoscopic views created from Visible 0.64 µm imagery (Band 3 for AHI, Band 2 for GOES-17).  That is shown below.  Thirty-minute timesteps are used because GOES-17 scans a full disk every 15 minutes (in Mode 3 that is currently operational; Mode 6, if used, scans a Full Disk every 10 minutes; and Mode 4, continuous Full Disk, the highest data rate for the GOES-R series, scans a Full Disk every 5 minutes). Himawari scans a Full Disk every 10 minutes. The three-dimensional representation facilitates the identification of warm conveyor belts associated with this developing storm. (This link shows the same animation but with the imagery flipped so it can be viewed in Google Daydream).

GOES-17 non-operational Visible (0.64 µm) imagery (left) and Himawari-8 Visible (0.64 µm) imagery (right), every half-hour from 2000 UTC on 15 January to 0400 UTC on 16 January (Click to animate)

Thanks to Mary Ellen Craddock, Northrop-Grumman, for the reminder that stereo imagery is possible with GOES-17 and Himawari.  (It should be even better with Himawari-8 and South Korea’s GEOKOMPSAT-2A!)

Blowing snow in southern Manitoba and the Red River Valley

January 15th, 2019 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, left) and Near-Infrared “Snow/Ice (1.61 µm, right) images, with hourly plots of surface wind and weather type [click to play animation | MP4]

A comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (above) revealed plumes of blowing snow originating over northern Lake Winnipeg and southern Lake Manitoba, lofted by strong northerly winds in the wake of a cold frontal passage. The blowing snow originating over the southern portion of Lake Manitoba was then then channeled southward into the Red River Valley (topography), with horizontal convective roll clouds eventually developing.

In a sequence of MODIS Visible (0.65 µm) and Snow/Ice (1.61 µm) images from Terra and Aqua in addition to VIIRS Visible (0.64 µm) and Snow/Ice (1.61 µm) from NOAA-20 and Suomi NPP (below), the plumes of blowing snow were also easier to detect in the Snow/Ice images (due to better contrast against the existing snow cover).

MODIS Visible (0.65 µm) and Snow/Ice (1.61 µm) images from Terra and Aqua plus VIIRS Visible (0.64 µm) and Snow/Ice (1.61 µm) from NOAA-20 and Suomi NPP [click to enlarge]

MODIS Visible (0.65 µm) and Snow/Ice (1.61 µm) images from Terra and Aqua plus VIIRS Visible (0.64 µm) and Snow/Ice (1.61 µm) from NOAA-20 and Suomi NPP [click to enlarge]

A closer view of the Lake Manitoba plume is shown below; surface observations indicated that visibility was reduced to 1/4 statute mile at locations such as Calilier ND (plot | text) and Hallock MN (plot | text).

NOAA-20 and Suomi NPP VIIRS Snow/Ice (1.61 µm) images, with plots of surface observations [click to enlarge]

NOAA-20 and Suomi NPP VIIRS Snow/Ice (1.61 µm) images, with plots of surface observations [click to enlarge]

An Aqua MODIS True Color Red-Green-Blue (RGB) image centered on Winnipeg, Manitoba (source)  is shown below.

Aqua MODIS True Color image [click to enlarge]

Aqua MODIS True Color image [click to enlarge]

Toggles between 250-meter resolution Terra/Aqua MODIS True Color and False Color RGB images (centered between Lake Manitoba and the North Dakota border) from the MODIS Today site (below) provided a more detailed view of the blowing snow streaming southeastward from Lake Manitoba into far northeastern North Dakota and far northwestern Minnesota.

Terra MODIS True Color and False Color RGB images [click to enlarge]

Terra MODIS True Color and False Color RGB images [click to enlarge]

Aqua MODIS True Color and False Color RGB images [click to enlarge]

Aqua MODIS True Color and False Color RGB images [click to enlarge]