Fog/stratus in the Strait of Juan de Fuca

May 20th, 2017 |

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

As seen in a Tweet from NWS Seattle/Tacoma (above), a plume of fog/stratus moved rapidly eastward through the Strait of Juan de Fuca on 20 May 2017. A closer view of GOES-16 Visible (0.64 µm) images (below; also available as an MP4 animation) shows the formation of “bow shock waves” as the leading edge of the low-level fog/stratus plume encountered the sharply-angled land surface of Whidbey Island at the far eastern end of the Strait near sunset — surface observations indicated that the visibility at Naval Air Station Whidbey Island was reduced to 0.5 mile just after the time of the final 0327 UTC image in the animation.

GOES-16 Visible (0.64 µm) images, with hourly plots of surface reports [click to play animation]

GOES-16 Visible (0.64 µm) images, with hourly plots of surface reports [click to play animation]

A Suomi NPP VIIRS Visible (0.6 µm) image with RTMA surface winds (below) indicated that westerly/northwesteerrrly wind speeds were generally around 15 knots at 21 UTC (just after the primary fog/stratus plume began to move into the western end of the Strait). Four hours later, there was a northwesterly wind gust of 27 knots at Sheringham, British Columbia (CWSP).

Suomi NPP VIIRS Visible (0.64 µm) images, with RTMA surface winds plotted in cyan [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) images, with RTMA surface winds plotted in cyan [click to enlarge]

During the following nighttime hours, a Suomi NPP VIIRS infrared Brightness Temperature Difference (11.45 – 3.74 µm) “Fog/Stratus Product” image at 0910 UTC (below) revealed that the fog/stratus plume covered much of the Strait (especially along the Washington coast), and that the leading edge had begun to spread both northward and southward from Whidbey Island. In addition, note the presence of a linear ship track (darker red enhancement) extending southwestward from Cape Flattery.

Suomi NPP VIIRS Infrared brightness temperature difference (11.45 - 3.74 µm)

Suomi NPP VIIRS infrared Brightness Temperature Difference (11.45 – 3.74 µm) “Fog/Stratus Product” image, with RTMA surface winds plotted in cyan [click to enlarge]

Bill Line (NWS Pueblo) showed the nighttime fog/stratus monitoring capability of a GOES-16 infrared Brightness Temperature Difference product:


On a side note, in the upper right portion of the GOES-16 (as well as the VIIRS) visible images one can also see the hazy signature of glacial sediment  flowing from the Fraser River westward into the Strait of Georgia. Longer-term changes in the pattern of this glacial sediment are also apparent in a comparison of Terra MODIS true-color Red/Green/Blue (RGB) images (source) from 20 April, 07 May and 20 May 2017 (below).

 

Terra MODIS true-color RGB images [click to enlarge]

Terra MODIS true-color RGB images [click to enlarge]

Eddy in Lake Michigan

April 8th, 2017 |

GOES-16 Visible (0.64 µm) images, with hourly surface and ship reports plotted in yellow [click to play animation]

GOES-16 Visible (0.64 µm) images, with hourly surface and ship reports plotted in yellow [click to play animation]

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

GOES-16 Visible (0.64 µm) images (above) revealed the presence of an eddy in the high-turbidity nearshore waters of southern Lake Michigan on 08 April 2017. The animation was created using 5-minute “CONUS” Sector images; an animation using 1-minute Mesoscale Sector images is available here.

A sequence of Terra and Aqua MODIS true-color Red/Green/Blue (RGB) images viewed using RealEarth (below) showed that the eddy began to develop on 07 April.

Terra and Aqua MODIS true-color RGB images from 07 and 08 April [click to enlarge]

Terra and Aqua MODIS true-color RGB images from 07 and 08 April [click to enlarge]

GOES-16 Visible and Cirrus Channels

March 21st, 2017 |

GOES-16 Visible (0.64 µm) images, 1202-1732 UTC on 21 March [click to play animated gif]

GOES-16 Visible (0.64 µm) images, 1202-1732 UTC on 21 March [click to play animated gif]

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

GOES-16 Visible imagery captured the erosion of near-surface clouds over Ohio on 21 March 2017. A benefit of the routine 5-minute imagery is that it allows better estimates of exactly when the low clouds will clear out. There is ample suggestion in the animation above of the presence of cirrus clouds. The GOES-16 ABI has a channel at 1.38 µm that is specifically designed to detect cirrus clouds because that is a region in the electromagnetic spectrum where strong water vapor absorption occurs. The animation of ‘cirrus channel’ imagery, below, confirms the presence of widespread cirrus clouds.

GOES-16 Cirrus Channel (1.38 µm) images, 1202-1732 UTC on 21 March [click to play animated gif]

GOES-16 Cirrus Channel (1.38 µm) images, 1202-1732 UTC on 21 March [click to play animated gif]

The MODIS instrument also has a similar near-infrared Cirrus spectral band — and a comparison of Terra MODIS Visible (0.65 µm) and Cirrus (1.375 µm) images at 1601 UTC is shown below.

Terra MODIS Visible (0.65 µm) and Cirrus (1.375 µm) images [click to enlarge]

Terra MODIS Visible (0.65 µm) and Cirrus (1.375 µm) images [click to enlarge]

GOES-16 Mesoscale Sectors: improved monitoring of fire activity

March 19th, 2017 |

GOES-16 Shortwave Infrared (3.9 µm, left) and GOES-13 Shortwave Infrared (3.9 µm, right) images [click to play MP4 animation]

GOES-16 Shortwave Infrared (3.9 µm, left) and GOES-13 Shortwave Infrared (3.9 µm, right) images [click to play MP4 animation]

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

The ABI instrument on GOES-16 is able to scan 2 Mesoscale Sectors, each of which provides images at 1-minute intervals. For what was likely a prescribed burn in the Francis Marion National Forest (near the coast of South Carolina) on 19 March 2017, a comparison of 1 minute Mesoscale Sector GOES-16 and 15-30 minute Routine Scan GOES-13 Shortwave Infrared (3.9 µm) images (above; also available as a 50 Mbyte animated GIF) demonstrated the clear advantage of 1-minute imagery in terms of monitoring the short-term intensity fluctuations that are often exhibited by fire activity. In this case,  the intensity of the fire began to increase during 15:15-15:45 UTC — a time period when there was a 30-minute gap in routine scan imagery from GOES-13. The GOES-16 shortwave infrared brightness temperature then became very hot (red enhancement) beginning at 15:46:58 UTC, which again was not captured by GOES-13 — even on the 16:00 UTC and later images (however, this might be due to the more coarse 4-km spatial resolution of GOES-13, compared to the 2-km resolution of the shortwave infrared band on GOES-16). Similar short-term intensity fluctuations of a smaller fire (burning just to the southwest) were not adequately captured by GOES-13.

The corresponding GOES-16 vs GOES-13 Visible image comparison (below; also available as a 72 Mbyte animated GIF) also showed the advantage of 1-minute scans, along with the improved 0.5-km spatial resolution of the 0.64 µm spectral band on GOES-16 (which allowed brief pulses of pyrocumulus clouds to be seen developing over the fire source region).

GOES-16 Visible (0.64 µm, left) and GOES-13 Visible (0.63 µm, right) images [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and GOES-13 Visible (0.63 µm, right) images [click to play MP4 animation]

 The rapid south-southeastward spread of the smoke plume could also be seen on true-color Red/Green/Blue (RGB) images from Terra/Aqua MODIS and Suomi NPP VIIRS, as viewed using RealEarth (below).

Terra MODIS, Aqua MODIS and Suomi NPP VIIRS true-color images [click to enlarge]

Terra MODIS, Aqua MODIS and Suomi NPP VIIRS true-color images [click to enlarge]