Metop-A ASCAT scatterometer data (above) showed surface wind speeds as high as 64 knots near the storm center while Michael was at Category 2 intensity just northwest of Cuba at 0307 UTC on 09 October 2018.

A toggle between Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 0752 UTC (below; courtesy of William Straka, CIMSS) revealed transverse banding north of the storm center on the Infrared image, and mesospheric airglow waves propagating westward away from Michael on the Day/Night Band image.

5-minute GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images from 0517-1332 UTC (below) showed a series of relatively brief convective bursts around the storm center, but in general Michael exhibited a somewhat disorganized appearance during that time period.

After sunrise, 1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) images (below) revealed the gradual formation of a more well-defined eye during the day, with episodic clusters of convective “hot towers” developing in the southeastern and eastern portions of the eyewall — which then rotated around to the north and northwest of the eye. By 18 UTC Michael had intensified to a Category 3 storm.

1-minute GOES-16 “Clean” Infrared Window images (below) indicated that infrared brightness temperatures associated with these hot towers were often as cold as -80º to -89ºC (violet to darker purple enhancement).

Michael had been encountering unfavorable deep-layer wind shear and had also been moving over a pocket of water with low Ocean Heat Content northwest of Cuba (below). However, once the hurricane began to move over waters having higher OHC in addition to warm Sea Surface Temperature, it gradually began to intensify from a Category 2 to a Category 3.

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GOES-17 data in this post are preliminary and non-operational

CONUS (Contiguous United States) imagery at 5-minute intervals from GOES-16 at 75.2 W Longitude and GOES-17 at 89.5 W Longitude allows for Hurricane Michael to be viewed stereroscopically from space. The animation above, starting at 1142 UTC and extending to sunset, (click here for an animated gif) shows an intensifying Michael with strong convection developing over the center.  To view in three dimensions, cross you eyes until 3 images are present, and focus on the image in the center.  Very strong shear is also apparent northeast of Michael.  Low-level winds and upper-level winds do not align, and convection there is strongly tilted.  (This graphic of shear is from the CIMSS Tropical Weather Website)

Sea-surface Temperatures over the Gulf (Source), below, show abundant warm water between Michael and its project landfall location along the northeast Gulf Coast (See the National Hurricane Center for latest information).

The animation shows the stereoscopic view on 9 October 2018. An animated gif is available here.

The animation below is shows Michael’s eye at full GOES-16/GOES-17 resolution starting at 1402 UTC on 9 October.

A full-resolution of Michael’s well-developed eye on 10 October is shown below.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (above) showed deep convection associated with Tropical Depression 14 east of Belize and the Yucatan Peninsula of Mexico early in the day on 07 October 2018. There was a large area of cloud-top infrared brightness temperatures in the -80ºC to -89ºC range (shades of purple), with isolated small pockets of -90ºC or colder (yellow enhancement).

1-minute GOES-16 “Red” Visible (0.64 µm) images from the UW-AOS site (below) showed numerous convective overshooting tops.

At 1655 UTC the system was upgraded to Tropical Storm Michael — 1-minute GOES-16 Infrared images (below) showed that deep convection persisted in the eastern semicircle of Michael during the remainder of the day.

A hint of the elongated low-level circulation could be seen just west of the deep convection on late-day GOES-16 Visible images (below).

===== 08 October Update =====

NOAA-20 VIIRS Day/Night Band (0.7 µm), Infrared Window (11.45 µm) and ATMS Microwave (88 GHz) images at 0721 UTC (above; courtesy of William Straka, CIMSS) indicated that a well-defined convective band was wrapping around the eastern, northern and northwestern portions of the storm center (with some bright lightning streaks showing up on the DNB image in the southeastern segment of this convective band).

In a comparison of DMSP-18 SSMIS Microwave (86 GHz) and GOES-16 Infrared Window (10.3 µm) images at or shortly after 1115 UTC (below), the Microwave imagery showed a very large eye beneath the convective clusters.

Michael was upgraded to a Category 1 hurricane at 15 UTC; 1-minute GOES-16 “Red” Visible (0.64 µm) images (below) revealed abundant deep convection around the core of the storm during the 3 hours leading up to that time.

Michael had been moving over very warm water since forming on 06 October; analyses of Ocean Heat Content and Sea Surface Temperature (below) showed that while the hurricane was forecast to briefly pass over a region of lower OHC in the far southeastern Gulf of Mexico, the remainder of its journey across the Gulf would be over water possessing modest amounts of OHC and warm SST values of 29-30ºC.

Similarly, a relatively cloud-free Terra MODIS Sea Surface Temperature product from 0343 UTC on 06 October (below) showed SST values of 84-85ºF (darker red colors) along much of the forecast path of Hurricane Michael (issued at 2100 UTC on 08 October).

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

A strong cold front (surface analyses | max/min temperatures) moved southward across the Plains states during the 03 October – 04 October 2018 period — and GOES-17 Upper-level Water Vapor (6.2 µm) images (above) revealed a distinct leeside frontal gravity wave as it propagated from southern Colorado and southern Kansas at 05 UTC to southeastern New Mexico and the southern Texas Panhandle by 20 UTC. Thunderstorms formed along the stalled residual wave along the New Mexico/Texas border after 1930 UTC.

Pilot reports of high-altitude “mountain wave” turbulence (below) were seen at 1559 and 1721 UTC, along the north-to-south oriented portion of the gravity wave that had become stationary over eastern New Mexico.

A 1-km resolution Aqua MODIS Water Vapor (6.7 µm) image at 0807 UTC (below) showed detailed gravity wave structure over Oklahoma.

A 3-panel comparison of GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images with plots of surface wind barbs (below) showed how the winds changed to northerly/northeasterly as the cold front passed.

Additional images of this event can be found on the Satellite Liaison Blog.

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