1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed  Category 1 Hurricane Douglas as it moved just north of Hawai’i during the day on 26 July 2020 (the boundary of the Mesoscale Sector was abruptly shifted westward at 1658 UTC). The coldest cloud-top infrared brightness temperatures were around -80ºC.

The apparent storm center as seen in satellite imagery was shifted north of the actual surface center location, due to the presence of southerly/southwesterly deep-layer wind shear as shown by a 20 UTC analysis from the CIMSS Tropical Cyclones site (above). This offset was also evident in a comparison of a DMSP-17 SSMIS Microwave (85 GHz) image at 1711 UTC with the analyzed surface position of Douglas at 1800 UTC (below).

===== 27 July Update =====

GOES-17 Visible and Infrared images (above) showed that the low-level circulation became exposed from the deep convection of Douglas a few hours after sunrise on 27 July, as it moved southwestward near the island of Nihoe. An analysis of deep-layer wind shear at 22 UTC (below) indicated the presence of 25-30 knots of southwesterly shear over that area — an unfavorable environment for tropical cyclone intensification/maintenance, in spite of the fact that the storm was moving over favorably-warm water.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed Category 1 Hurricane Hanna making landfall along the South Coast of Texas at 2200 UTC on 25 July 2020. The coldest cloud-top infrared brightness temperature was -88.6ºC at 1633 UTC. Winds gusted to 76 mph at Buoy 42020, and at 18 UTC a ship about 30 miles off the Texas coast reported blowing spray.

GOES-16 GLM Flash Extent Density (below) showed little to no lightning activity within the immediate eyewall region of Hurricane Hanna during the 9 hours leading up to landfall; however, lighting did increase somewhat after the 22 UTC landfall.

A comparison of time-matched Infrared images from Suomi NPP and GOES-16 ABI (below) showed the effect of parallax displacement, even at the relatively low latitudes of South Texas. The coldest cloud-top infrared brightness temperature on the VIIRS image was -86ºC, compared to -81ºC on the ABI image (the same color enhancement is applied to both images).

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Real Earth captured the cold cloud tops associated with vigorous convection with tropical storm Gonzalo shortly after midnight on 24 July 2020.   The VIIRS Imagery from NOAA-20, above, (the day’s NOAA-20 passes in the region (from this site) are shown here) shows numerous cloud tops colder than -80ºC (the purple enhancement).

True-color imagery from GOES-16, below, at 1210 UTC (from an experimental CSPPGeo-driven website at CIMSS), shows the storm off the coast of South America.  It does not appear to be well-organized.

GOES-16 imagery, below, from 1230 UTC, shows the small nature of Tropical storm Gonzalo as it sits north of South America. It is smaller than the very large tropical wave coming off the coast of Africa, for example, and smaller than the cluster of thunderstorms to its east, and smaller than the cluster of thunderstorms north of Hispaniola and Puerto Rico.  Small storms are often very susceptible to weakening effects in hostile environments.

The toggle below of the GOES-16 Split Window (10.3 µm – 12.3 µm, color-enhanced to bring out dry air — in yellow, red and pink — as might be associated with a Saharan Air Layer) and the Air Mass RGB, both taken from this website, show the inhibiting factor (moisture-rich tropical air is green in the RGB; drier air has an orange tint) that might prevail in Gonzalo’s future: the South American Continent is to the storm’s south; dry air prevails to the north and east of Gonzalo. What is a storm to do? The forecast from the National Hurricane Center is for the storm to rake the Windward Islands with tropical storm-force winds and subsequently dissipate. Interests in northern South America and the Windward Islands, and indeed all of the Caribbean, should continue to monitor the storm.

NUCAPS data also shows the dry environment surrounding the storm. The 850-500 mb relative humidity field, below, from two NOAA-20 passes, one near 0415 UTC and one near 0545 UTC, show the dry air north and east of the storm. (Gonzalo during this time was near 10ºN Latitude and 50ºW Longtiude)

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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 formation of Hurricane Douglas — the first hurricane of the 2020 season in the East Pacific Ocean — on 22 July 2020. Douglas was the 4th latest formation of the first hurricane on record in this basin.

===== 23 July Update =====

Douglas intensified to a Category 3 storm during the nighttime hours — 1-minute GOES-17 Visible and Infrared images during the first 4 hours of daylight on 23 July (above) revealed mesovortices within the eye of the hurricane. The coldest cloud-top infrared brightness temperature during this time period was -76.6ºC, associated with an overshooting top within the eyewall just north-northwest of the eye at 1701 UTC (below).

A Suomi NPP VIIRS Infrared Window (11.45 µm) image viewed using RealEarth (below) showed Hurricane Douglas at 1035 UTC, about 1.5 hours after it reached Category 3 intensity.

Later in the day, a toggle between NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images (below) showed Douglas at 2233 UTC.

===== 24 July Update =====

A Mesoscale Domain Sector was once again positioned over Category 3 Hurricane Douglas at 1945 UTC on 24 July — 1-minute GOES-17 Visible and Infrared images are shown above.

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