Contrails off the coast of Southern California

April 23rd, 2018 |

As pointed out by NWS San Diego, an interesting pattern of contrails formed off the coast late in the day on 23 April 2018. A comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm), Near-Infrared “Cirrus” (1.37 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed signatures during the daylight hours — Visible images revealed contrail shadows being cast upon the low-altitude cloud tops at 0142 and 0147 UTC — with an Infrared signature persisting after sunset. These contrails were likely caused by military aircraft performing training exercises, since chaff was seen with radar in that same area on the previous day.

GOES-16

GOES-16 “Red” Visible (0.64 µm, left), Near-Infrared “Cirrus” (1.37 µm, center) and “Clean” Infrared Window (10.3 µm, right) images [click to play animation | MP4]

A better post-sunset signature was seen on a NOAA-15 Infrared Window (10.8 µm) image at 0212 UTC (below). A comparison with the corresponding GOES-16 “Clean” Infrared Window (10.3 µm)  image displayed a significant northwestward GOES-16 displacement due to parallax — and the 1.1 km spatial resolution of AVHRR data resulted in a clearer contrail signature.

NOAA-15 AVHRR Infrared Window (10.8 µm) and GOES-16 ABI

NOAA-15 AVHRR Infrared Window (10.8 µm) and GOES-16 ABI “Clean” Infrared Window (10.3 µm) images [click to enlarge]

The pattern of contrails could also be followed after sunset using GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) imagery (below).

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play animation | MP4]

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play animation | MP4]

The GOES-16 Water Vapor weighting function plots (below) displayed a bi-modal distribution for all 3 spectral bands, with peaks near 300 hPa and 500 hPa. The absence of a distinct contrail signature on the 6.2 µm imagery suggests that these features were located closer to the 500 hPa pressure level.

GOES-16 Water Vapor weighting functions, calculated using rawinsonde data from San Diego CA [click to enlarge]

GOES-16 Water Vapor weighting functions, calculated using rawinsonde data from San Diego CA [click to enlarge]

2 structural fires: Beaver Dam, Wisconsin and San Francisco, California

March 17th, 2018 |

GOES-16 Shortwave Infrared (3.9 µm, left) and

GOES-16 Shortwave Infrared (3.9 µm, left) and “Red” Visible (0.64 µm, right) images, with hourly surface reports plotted in yellow [click to play animation]

As documented by NWS Milwaukee/Sullivan, the controlled burn of an apartment building occurred during the late morning hours on 15 March 2018. A comparison of GOES-16 (GOES-East) Shortwave Infrared (3.9 µm) and “Red” Visible (0.64 µm) images (above) displayed subtle “hot spot” signatures (darker red pixels, circled) as well as an occasional hint of a small smoke plume during the early phase of the fire. At the bottom of the images, note the appearance of a few larger and hotter fires (black pixels) in northern Illinois — likely agricultural fires to prepare fields for Spring planting.

2 days later, another structure fire occurred in the San Francisco area during the early evening hours of 17 March 2018:

Hot spot signatures were observed on the 0247 UTC and 0252 UTC (7:47 and 7:52 PM local time) Shortwave Infrared (3.9 µm) images, along with subtle lighter gray pixels on the Near-Infrared (2.24 µm) images (below).

GOES-16 Shortwave Infrared (3.9 µm, left) and Near-Infrared (2.24 µm, right) images, with station identifiers plotted in cyan [click to play animation]

GOES-16 Shortwave Infrared (3.9 µm, left) and Near-Infrared (2.24 µm, right) images, with airport identifiers plotted in cyan [click to play animation]

A timely overpass of the NOAA-15 satellite scanned the fire at 02:43:50 UTC (7:43:50 PM local time), showing a well-defined hot spot (darker red enhancement) on the 1-km resolution Shortwave Infrared (3.7 µm) image (below).

NOAA-15 Shortwave Infrared (3.7 µm) image [click to enlarge]

NOAA-15 Shortwave Infrared (3.7 µm) image [click to enlarge]

Tornado near Eureka, California

January 25th, 2018 |


A waterspout moved inland near the NWS Eureka forecast office during the late afternoon hours on 25 January 2018. The brief tornado caused some EF-0 damage (interestingly, it was the only report of severe weather in the US that day, and the first tornado in the Eureka forecast area since 1998).

A comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed the line of convection as it moved across the area (Eureka and the location of the 0040-0041 UTC tornado are a few miles south-southwest of the airport KACV) — the coldest cloud-top infrared brightness temperatures on the 0037 UTC and 0042 UTC GOES-16 images were -30.7ºC (dark blue color enhancement). Note: there were no western US images available from GOES-15 (GOES-West) between 0030 and 0100 UTC, due to a routine “New Day Schedule Transition” and a 0051 UTC Southern Hemisphere scan.

GOES-16

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images, with plots of hourly surface reports [click to play animation]

There was an overpass of the NOAA-19 satellite about 2 hours prior to the Eureka tornado, at 2251 UTC. If we compare the NOAA-19 Visible (0.63 µm) image to the corresponding GOES-16 Visible (0.64 µm) image (below), a parallax shift to the west is evident with GOES-16 (which was scanning that same scene only 24 seconds later than NOAA-19: 22:52:23 UTC vs 22:51:59 UTC).

NOAA-19 and GOES-16 Visible images at 2252 UTC, with plots of 23 UTC surface reports [click to enlarge]

NOAA-19 and GOES-16 Visible images at 2252 UTC, with plots of 23 UTC surface reports [click to enlarge]

In the corresponding Infrared Window images from NOAA-19 (10.8 µm) and GOES-16 (10.3 µm) (below), the parallax shift was also apparent — and the coldest cloud-top infrared brightness temperatures associated with the convection just northwest of KACV were -36.2ºC and -35.2ºC, respectively. Given the very high viewing angle for GOES-16 (about 67 degrees over Eureka), the qualitative and quantitative satellite presentation compared quite favorably to that seen from the more direct overpass of NOAA-19.

NOAA-19 and GOES-16 Infrared Window images at 2252 UTC, with plots of 23 UTC surface reports [click to enlarge]

NOAA-19 and GOES-16 Infrared Window images at 2252 UTC, with plots of 23 UTC surface reports [click to enlarge]

As mentioned in the afternoon Area Forecast Discussion, offshore Sea Surface Temperature (SST) values were in the 50-55ºF range; this was also seen in a comparison of the nighttime and daytime MODIS SST product (below). With the presence of cold air aloft and relatively warm water at the surface, the lower troposphere was unstable enough to support the development and growth of showers and thunderstorms.

MODIS Sea Surface Temperature product [click to enlarge]

MODIS Sea Surface Temperature product [click to enlarge]

Lake Michigan Mesovortex

December 31st, 2017 |

1-minute GOES-16

1-minute GOES-16 “Red” Visible (0.64 µm) images, with hourly surface reports plotted in yellow [click to play MP4 animation]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a well-defined mesoscale vortex (or “mesovortex”) moving southward across southern Lake Michigan on 31 December 2017. The default western GOES-16 Mesoscale Sector provided images at 1-minute intervals. This feature was responsible for brief periods of heavy snow at locations such as South Haven, Michigan KLWA (beginning at 1455 UTC), Benton Harbor, Michigan KBEH (beginning at 1625 UTC) and La Porte, Indiana KPPO (from 2055 to 2115 UTC).

Comparisons of POES AVHRR/Terra MODIS/Suomi NPP Infrared (10.8 µm/11.0 µm/11.45 µm) and Visible (0.86 µm/0.65 µm/0.64 µm) images along with an overlay of the corresponding Real-Time Mesoscale Analysis (RTMA) surface winds (below) provided views of the mesovortex at 1522 UTC, 1714 UTC and 1852 UTC, respectively.

POES AVHRR Infrared (10.8 µm) and Visible (0.86 µm) images at 1522 UTC, with 15 UTC RTMA surface winds [click to enlarge]

POES AVHRR Infrared (10.8 µm) and Visible (0.86 µm) images at 1522 UTC, with 15 UTC RTMA surface winds [click to enlarge]

Terra MODIS Infrared (11.0 µm) and Visible (0.65 µm) images at 1714 UTC, with 17 UTC RTMA surface winds [click to enlarge]

Terra MODIS Infrared (11.0 µm) and Visible (0.65 µm) images at 1714 UTC, with 17 UTC RTMA surface winds [click to enlarge]

Suomi NPP Infrared (11.45 µm) and Visible (0.64 µm) images at 1852 UTC, with 19 UTC RTMA surface winds [click to enlarge]

Suomi NPP Infrared (11.45 µm) and Visible (0.64 µm) images at 1852 UTC, with 19 UTC RTMA surface winds [click to enlarge]

During the preceding nighttime hours, a comparison of Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0729 UTC along with an overlay of 07 UTC RTMA surface winds (below) showed in spite of patchy thin cirrus clouds over the region, ample illumination from the Moon (which was in the Waxing Gibbous phase, at 96% of Full) enabled a signature of the early stage of mesovortex formation to be seen on the Day/Night Band (DNB) image. Ice crystals within the thin cirrus clouds were responsible for the significant scattering city light signatures on the DNB image.

Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0729 UTC, with 07 UTC RTMA surface winds [click to enlarge]

Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0729 UTC, with 07 UTC RTMA surface winds [click to enlarge]

As an aside, it is interesting to note that ice could be seen in the nearshore waters of Lake Michigan — both in the western part of the lake, off the coast of Wisconsin and Illinois, and in the eastern part of the lake off the coast of Lower Michigan. The lake ice appeared as darker shades of cyan in the 250-meter resolution Terra MODIS false-color (Band 7-2-1 combination) Red-Green-Blue (RGB) image from the MODIS Today site (below).

Terra MODIS true-color and false-color images over southern Lake Michigan [click to enlarge]

Terra MODIS true-color and false-color images over southern Lake Michigan [click to enlarge]