* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

After its final 2 days of northward motion as a Category 1 storm well southeast of the Outer Banks of North Carolina, Hurricane Maria was downgraded to a Tropical Storm at 2100 UTC on 26 September 2017. A comparison of the 2345 UTC September GOES-13 (GOES-East) Infrared Window (10.7 µm) image and an overlay of the 00 UTC 27 September Deep-Layer Wind Shear product (above) showed that Maria had been moving northward into an environment of increasing northeasterly shear, aiding the decrease of storm organization and intensity. However, due to the large size of the strong wind field associated with Maria, surface wind gusts as high as 59 mph were reported along the Outer Banks.

The effect of increasing wind shear was obvious in the satellite presentation of GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) — the low-level circulation center (LLCC) was becoming more exposed with time, while deep convection remained southeast of the LLCC.

The entrainment of dry air into the northern semicircle of Maria was evident as a warming/drying trend depicted on GOES-16 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below).

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Mostly clear skies over Puerto Rico early on 25 September 2017 allowed the Day Night Band on Suomi NPP to observe man-made sources of light on that island as shown in the image above (Courtesy of William Straka, CIMSS).  (A previous example on this blog showed lights through clouds).  A similar view is available at NASA’s Worldview site, or at Real Earth. The Lunar Phase on 25 September 2017 is Waxing Crescent with 26% illumination; similar illumination occurred on 24 August, and a link to the Day Night Band imagery at NASA Worldview on that day is here. The differences are stark.

A RealEarth examination of two Suomi NPP VIIRS Day/Night Band (0.7 µm) images — an archived “clear sky” view from 31 December 2015, and an “after-Maria” image from 26 September 2017 (below) — provides a good before/after comparison showing a reduction in the amount of city light illumination following the passage of the hurricane.

The Infrared Imagery, below, suggests a few clouds over northwest Puerto Rico. Such clouds could alter the perception of light sources in that region.

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* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

Hurricane Maria was downgraded to a Category 2 storm at 12 UTC on 24 September 2017 (above), when it was located about halfway between Miami and Bermuda.

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed a close-up view of the eye region of Maria during the daylight hours.

Due to the large size of the radius of Tropical Storm force winds, a Tropical Storm Watch was issued late in the day for the Outer Banks and adjacent inland areas of North Carolina (below).

UPDATE: 12 hours later, much of the Tropical Storm Watch was upgraded to a Tropical Storm Warning.

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GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing

Hurricane Maria presented a very interesting eye structure during the course of the day on 21 September 2017, as shown in the mp4 animation above (also available as a YouTube video).  The animation shows 10.3 µm imagery every 2 minutes from 0849 UTC through 2122 UTC on 21 September 2017.

Pete Pokrandt, at the University of Wisconsin Atmospheric and Oceanic Sciences Department, created a similar animation using the 0.64 µm Visible channel on GOES-16.

30-second interval (using overlapping 1-minute interval Mesoscale Sector) GOES-16 Visible (0.64 µm) and Infrared Window (10.3 µm) images covering the 6-hour period from 1031-1631 UTC are shown below. During this time, Maria re-intensified to a Category 3 hurricane, with the eye centered just off the northeastern coast of the Dominican Republic.

For more information on Maria, visit the National Hurricane Center website.  The CIMSS Tropical Weather Website has information as well.

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