Sally was upgraded to a Hurricane at 1600 UTC on 14 September. (Link)

Hurricane warning have been issued along the central Gulf Coast on 14 September as strengthening tropical storm Sally approached.  MIMIC estimates of total precipitable water, above, for the 24 hours ending at 11 UTC on 14 September show the moist airmass in the Gulf that is helping to sustain the storm.  (Also apparent in the imagery:  Hurricane Paulette, moving over the island of Bermuda, and Pacific Tropical Storm Karina.  (For more information on these storms (and other storms during this active Atlantic Hurricane Season), and for the latest on Sally, refer to the National Hurricane Center)

Both Suomi NPP and NOAA-20 overflew Sally between 0700 and 0800 UTC on 14 September, and Day Night Band imagery for the storm (source) is shown below. The 50-minute time step between the two images show little because of a lack of lunar illumination, but westward expansion of the cloud shield near the Mississippi River delta is apparent. This suggests adequate upper-level divergence for continued storm intensification.

GOES-16 animations of infrared imagery for the 12 hours endings near 1300 UTC on 14 September, below, also show an expansion in the size of the coldest cloud tops in the storm’s center. A frontal zone is also apparent in the infrared imagery, stretching from New York/Pennsylvania southwestward to north Texas. This front will limit how far north the effects of Sally — post landfall — can move. (The forecast as of 14 September moves the post-landing remnants of Sally through Georgia).

Low-level Water vapor infrared imagery (GOES-16 Band 10, at 7.3 µm; click here for the Upper-level Water vapor infrared imagery, at 6.2 µm), below, using an enhancement courtesy William Churchill, WFO Key West (Click here for the Band 10 animation with a more familiar, perhaps, ‘dry yellow’ enhancement), also shows the expansion of the clouds in the central core of the storm. An apparent outflow channel from the storm south over Cuba also shows up in the animation.

A GOES-16 mesoscale sector is viewing the development of Sally, allowing for 1-minute imagery.  Visible imagery below, for two hours shortly after sunrise, shows active convection ongoing in the center of the storm and an obvious expansion of the central dense overcast. Both things support strengthening is the inner core structure.

===== 21 UTC Update =====

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images — with and without an overlay of GLM Flash Extent Density (above) showed Hurricane Sally after it was upgraded to a Category 2 storm at 21 UTC. A series of convective bursts could be seen developing near the center of Sally; as is usually the case, very little GLM-detected lightning activity was associated with these types of convective bursts located within close proximity to the eye. Winds at Viocsa Knoll — an elevated oil platform, located just northwest of the storm center — gusted to 94 knots or 108 mph at 2100 UTC (shortly after gusting to 102 knots or 117 mph at 2020 UTC).

You can find more information on Sally at the SSEC Tropical Website (Link). For official forecasts, refer to the pages of the National Hurricane Center. Interests along the central Gulf Coast should be preparing for the arrival of this storm, in addition to monitoring its progress.

View only this post Read Less

Hurricane Gilbert (1988) is one of the most intense Atlantic-basin hurricane on record. NOAA’s GOES-7 offer both visible and infrared views of the storm. These images are from the VISSR mode. What is unique about the view from the geostationary orbit, is that it allows both large / synoptic scale views as well as finer (mesoscale) views. 

Visible band

A week-long visible loop of the Hurricane Gilbert as it moves across the Caribbean and through the Gulf of Mexico. Tropical Storm Florence can also be seen near Louisiana, early in the animation. 

A GOES-7 visible loop over the time period of maximum intensity. 

The highest spatial resolution visible GOES-17 imagery of Hurricane Gilbert. Note the horizontal striping due to the photo-multipler tube technology that was then used. 

Infrared window band

Above is a “large-scale” view of the GOES-7 infrared longwave window band covering September 10-18, 1988. Tropical Storm Florence can also be seen near Louisiana, early in the animation. 

A more “zoomed in” view:

All the IR images have been color-enhanced to highlight the coldest temperatures. 

Visible and Infrared window bands

A much larger file (18 MB) of the same day/time as above. This is a combined image, with the visible band, along with the cold pixels from the infrared band (color). 

Swipe between GOES-7 Visible and Infrared bands.

Fade between GOES-7 Visible and Infrared bands. (Using this software.)

NOAA GOES-7 data are via the University of Wisconsin-Madison SSEC Satellite Data Services.

 

View only this post Read Less

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm), Fire Temperature Red-Green-Blue (RGB) + GLM Flash Extent Density (FED) and “Clean” Infrared Window (10.35 µm) images (above) showed the formation of a pyrocumulonimbus (pyroCb) cloud over the Bear Fire (part of the North Complex) in Northern California on 09 September 2020. The coldest cloud-top infrared brightness temperatures were -61.4ºC; no GLM-detected lightning activity was seen with this pyroCb. 

A comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images (below) displayed the initial 2 pyroCb cloud pulses shortly after their formation. Side-illumination from the Moon (which was in the Waning Gibbous phase, at 59% of Full) allowed for a distinct shadow to be cast northwest of the colder/taller pyroCb pulse — and the pyroCb clouds exhibited a darker appearance than the layer of low-altitude smoke to the west, likely due to very high amounts of fresh smoke contained within the rapidly-rising cloud turrets.

A toggle between time-matched Infrared Window images of the Bear Fire pyrocumulonimbus cloud from Suomi NPP (SNPP) and GOES-17 (below) highlighted the differences in spatial resolution — 375-m with SNPP VIIRS, vs 2-km (at satellite sub-point) with GOES-17 ABI — and the parallax displacement inherent with GOES-17 imagery at that location (17 km for a 15.2-km tall cloud top). The coldest cloud-top infrared brightness temperature was -76.2ºC with SNPP, vs -59.9ºC with GOES-17 (identical color enhancements were applied to both images).

GOES-17 True Color Red-Green-Blue (RGB) images created using Geo2Grid (below) showed the southward drift of the high-altitude pyroCb cloud material during the day, along with widespread dense smoke that covered much of California at lower altitudes.

View only this post Read Less

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm), GOES-17 Shortwave Infrared (3.9 µm), Fire Temperature Red-Green-Blue (RGB) + GLM Flash Extent Density (FED) and “Clean” Infrared Window (10.35 µm) images (above) showed the formation of a pyrocumulonimbus (pyroCb) cloud over the Hopkins Fire in Northern California on 08 September 2020.

The vertical extent of the pyroCb cloud tower was even more apparent when viewed in Visible imagery from GOES-16 (GOES-East), displayed in the top left panel of the animation below.

Later in the day and farther to the east, 1-minute GOES-17 imagery (below) showed the development of another pyroCb cloud over the North  Complex. Unfortunately, there was a ~1-hour gap in images (from 2034 to 2130 UTC) when a yaw flip maneuver was performed on the satellite.

However, during this yaw flip maneuver the pyroCb formation and propagation could be followed using 5-minute imagery from GOES-16 (below). As the lower-latitude portion of the smoke plume associated with this fire flare-up drifted south-southwestward, it restricted the surface visibility to 2.5 miles at Beale Air Force Base (KBAB).

View only this post Read Less