GOES-18 is currently serving as GOES-West

August 1st, 2022 |

GOES-18 “Red” Visible (0.64 µm) and Mid-level Water Vapor (6.9 µm) images [click to play animated GIF | MP4]

Beginning at 1713 UTC on 01 August 2022, GOES-18 began serving as GOES-West during an operational interleave period — so GOES-18 imagery routinely became available in AWIPS. Examples of GOES-18 “Red” Visible (0.64 µm) and Mid-level Water Vapor (6.9 µm) images from a combination of the Alaska, Pacific-US (PACUS) and Hawai`i Sectors are shown above.

GOES-18 multi-panel images of the PACUS Sector (below) displayed all 16 spectral bands of the ABI instrument.

GOES-18 multi-panel images of the PACUS Sector [click to play animated GIF |MP4]

A closer view of GOES-18 multi-panel images centered on Tropical Storm Frank is shown below.

GOES-18 multi-panel images of Tropical Storm Frank [click to play animated GIF | MP4]

Farther to the north, GOES-18 Visible images centered over Alaska (below) revealed an impressive southwesterly surge of stratus across the Chukchi Sea, which was moving toward the Bering Strait and the coast of Siberia (where some sea ice could be seen along the coast and offshore).

GOES-18 “Red” Visible (0.64 µm) images [click to play animated GIF | MP4]

GOES-18 ABI data also replaced GOES-17 as GOES-West for users receiving imagery via GRB download. Some examples created by Tim Schmit (NOAA/NESDIS/ASPB) — using GOES-18 imagery downloaded by SSEC Satellite Data Services — are shown below.

This transition to GOES-18 will mitigate the degraded GOES-17 infrared imagery caused by its Loop Heat Pipe cooling issues. The Loop Heat Pipe system was re-designed for the GOES-18 ABI instrument. 

16-panel comparisons of GOES-17 and GOES-18 ABI imagery at 1230 UTC [click to enlarge]

Additional information and examples can be found on the Satellite Liaison Blog.


Using SAR Winds to center-fix Tropical Cyclone Estelle in the Eastern Pacific

July 20th, 2022 |
OGES-17 Visible (Band 2, 0.64 µm) and Infrared (Band 13, 10.3 µm) at 0150 UTC on 20 July 2022 (click to enlarge)

GOES-17 visible and infrared imagery shows Tropical Storm Estelle over the eastern Pacific to the west-southwest of Baja California. Although there are regions of strong convection, satellite presentation of the storm suggests a modest tropical storm. Center-fixing a storm such as this (with just one image vs. an animation!) is complicated by both parallax (GOES-17 is overhead at 0oN, 137.2oW) and the lack of an easily-discerned eye feature in this system.

Instruments that view surface winds, via Scatterometry or via Synthetic Aperture Radar (SAR), can offer better center fixes. Consider the toggle below of Radarsat-2 SAR winds over Estelle. SAR Winds (available here; SAR winds over Tropical Systems can be found here.) show a lopsided storm, with most of the strong winds on the poleward side of the center. The SAR winds that use 0.5-degree GFS wind data as a first guess show a characteristic hourglass feature near the center that advertises an ambiguity between the first guess winds and the observations. That feature is missing in the SAR wind field that is a product of the 0.25-degree GFS winds, suggesting that the 0.25-degree wind field is more accurate. Both fields show a rather baggy center at or just south of 20oN.

RSAT-2 SAR Winds over Estelle benchmarked by 0.5-degree and 0.25-degree model output, 0150 UTC on 20 July 2022; note the different color scales used in the two images (Click to enlarge)

Scatterometry from MetopB and HY2B between 1730 UTC 19 July and 0230 UTC 20 July, respectively show a storm moving west-northwest, passing north of 20oN just after 0230 UTC.

ASCAT (MetopB) and HY2B Scatterometry winds at 1730 (19 July) and 0230 (20 July), respectively.

Dry (and dusty) air over the Caribbean

July 12th, 2022 |
Hourly True Color imagery over the Caribbean, 1300 – 2000 UTC on 12 July 2022

CSPP True Color imagery (link) above suggests a region of apparent dust over the eastern Caribbean Sea. That is, there is a hazy look to the imagery that persists even as the region of sun glint moves past. Suspended dust in the tropical Atlantic is known to suppress convection. Other products besides true-color imagery can be used to show dry the air (qualitatively and quantitatively) over the Caribbean. For example, the toggle below (from this site) of the Saharan Air Layer analysis (via the Split Window Difference) and the Airmass RGB shows very dry air south of Hispaniola and Puerto Rico — orange in the Split Window Difference, and also an orange tint to the Airmass RGB.

Saharan Air Layer analysis and Airmass RGB, 1800 UTC on 12 July 2022 (Click to enlarge)

Air over the eastern Caribbean also shows large values of Aerosol Optical Depth (from the AerosolWatch site); the enhanced values are most likely a result of suspended dust from the Sahara. AOD is not computed in the region of sun glint — that’s the cause of the smooth curved line that arcs through extreme eastern Cuba.

Aerosol Optical Depth at 1950 UTC on 12 July 2022 (Click to enlarge)

Total Precipitable Water (TPW) from the MIMIC site (link) shows dry air over the eastern Caribbean (and over much of the tropical Atlantic Ocean north of 10oN). Total precipitable water derived from gridded NUCAPS fields (here), and relative humidity at 700 mb (here), also show dry air over the eastern Caribbean; they are also shown in a toggle with NUCAPS Quality Flags below.

MIMIC Total Precipitable Water, 2000 UTC on 11 July – 1900 UTC 12 July 2022 (click to enlarge)
Gridded NUCAPS Fields: Quality Flags, Relative Humidity at 700 mb, Total Precipitable Water, 1744 UTC on 12 July 2022 (click to enlarge)

An interesting feature in the animation at the top of this blog post is the development of convection over Hispaniola, over the topography, even in the presence of fairly dry air. NUCAPS analyses of 500-mb air temperature (here), show a cold pocket of air over Puerto Rico and Hispaniola, helping the development of convection there.

When assessing the environment of a region with sparse conventional data, such as the Atlantic (or Pacific) Ocean, or the Caribbean Sea, take advantage of information that satellite observations can give you.

Hurricane Darby in the East Pacific Ocean

July 11th, 2022 |

GOES-17 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.35 µm, bottom) images [click to play animated GIF | MP4]

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed the evolution of the eye of Hurricane Darby as it moved westward across the East Pacific Ocean on 11 July 2022. Mesovortices were evident within the eye, along with a stadium effect eye structure — as Darby ended its period of rapid intensification and leveled off as a Category 4 storm (ADT | SATCON). Darby was moving through an environment of low wind shear and across relatively warm water (SST | OHC), factors which favored intensification.

A NOAA-20 VIIRS Infrared Window (11.45 µm) image from RealEarth (below) revealed an arc of slightly colder cloud tops (shades of white within dark black) in the northern portion of the eyewall.

NOAA-20 VIIRS Infrared Window (11.45 µm ) image at 2129 UTC [click to enlarge]

A NOAA-20 ATMS Microwave (183 GHz) image from the CIMSS Tropical Cyclones site (below) also showed the compact eye, along with a band of precipitation spiraling northward.

NOAA-20 ATMS Microwave (183 GHz) image at 2129 UTC [click to enlarge]