Wildfires in Northern California

October 9th, 2017 |

GOES-16 Shortwave Infrared (3.9 µm) images, with county outlines plotted in gray (dashed) and surface station identifiers plotted in white [click to play MP4 animation]

GOES-16 Shortwave Infrared (3.9 µm) images, with county outlines plotted in gray (dashed) and surface station identifiers plotted in white [click to play MP4 animation]

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

GOES-16 Shortwave Infrared (3.9 µm) images (above) showed the “hot spot” signatures (black to yellow to red pixels) associated with numerous wildfires that began to burn in Northern California’s Napa County around 0442 UTC on 09 October 2017 (9:42 PM local time on 08 October). A strong easterly to northeasterly Diablo wind (gusts) along with dry fuels led to extreme fire behavior, with many of the fires quickly exhibiting very hot infrared brightness temperature values and growing in size at an explosive rate (reportedly burning 80,000 acres in 18 hours).

A comparison of nighttime GOES-16 Shortwave Infrared (3.9 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (below) offered another example of nocturnal fire signature identification — the bright glow of the fires showed up well on the 1-km resolution 1.61 µm imagery. Especially noteworthy was the very rapid southwestward run of the Tubbs Fire, which eventually moved just south of station identifier KSTS (Santa Rosa Sonoma County Airport; the city of Santa Rosa is located about 5 miles southeast of the airport. These Northern California fires have resulted in numerous fatalities, destroyed at least 3500 homes and businesses, and forced large-scale evacuations (media story).

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

GOES-16 Shortwave Infrared (3.9 µm, left) and Near-Infrared “Snow/Ice” (1.61 µm, right) images [click to play MP4 animation]

A toggle between 1007 UTC (3:07 AM local time) Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images (below) provided a view of the fires at an even higher spatial resolution. Since the Moon was in the Waning Gibbous phase (at 82% of Full), it provided ample illumination to highlight the dense smoke plumes drifting west-southwestward over the adjacent offshore waters of the Pacific Ocean.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

A closer VIIRS image comparison (with county outlines) is shown below.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

A comparison of Suomi NPP VIIRS true-color and false-color Red/Green/Blue (RGB) images from RealEarth (below) helped to discriminate between smoke and cloud features offshore over the Pacific Ocean.

Suomi NPP VIIRS True-color and False-color RGB images [click to enlarge]

Suomi NPP VIIRS True-color and False-color RGB images [click to enlarge]

===== 10 October Update =====

Suomi NPP VIIRS true-color and false-color images [click to enlarge]

Suomi NPP VIIRS true-color and false-color images [click to enlarge]

With the switch to southwesterly surface winds on 10 October, smoke plumes could be seen moving northeastward on RealEarth VIIRS true-color imagery, while the burn scars of a number of the larger fires became apparent on VIIRS false-color RGB imagery (above).

===== 12 October Update =====

Suomi NPP VIIRS true-color RGB images, with VIIRS-detected fire locations [click to enlarge]

Suomi NPP VIIRS true-color RGB images, with VIIRS-detected fire locations [click to enlarge]

A transition back to northerly winds on 12 October helped to transport the wildfire smoke far southward over the Pacific Ocean (above). Smoke was reducing surface visibility and adversely affecting air quality at locations such as San Francisco (below).

Time series plot of surface observations at San Francisco International Airport [click to enlarge]

Time series plot of surface observations at San Francisco International Airport [click to enlarge]

Suomi NPP VIIRS Aerosol Optical Depth values were very high — at or near 1.0 — within portions of the dense smoke plume (below).

Suomi NPP VIIRS true-color RGB image and Aerosol Optical Depth product [click to enlarge]

Suomi NPP VIIRS true-color RGB image and Aerosol Optical Depth product [click to enlarge]

Mostly Clear Skies over Puerto Rico

September 25th, 2017 |

Suomi NPP Day Night Band Visible (0.7 µm) Imagery, 0619 UTC on 25 September 2017 (Click to enlarge)

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.

Suomi NPP VIIRS Day/Night Band (0.7 µm) images: an  archived

Suomi NPP VIIRS Day/Night Band (0.7 µm) images: an archived “clear sky’ view from 31 December 2015, and a “after-Maria” image from 26 September 2017 [click to enlarge]

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

Suomi NPP VIIRS Infrared (11.45 µm) Imagery, 0619 UTC on 25 September 2017 (Click to enlarge)

Puerto Rico after Maria

September 21st, 2017 |

Suomi NPP Day Night Band Visible (0.7 µm) Imagery, ~0600 UTC, 21 September 2017 (Click to enlarge)

Suomi NPP Overflew Puerto Rico at ~0555 UTC on 21 September, and the Day Night Band Visible Imagery (0.7 µm), above (from Real Earth, direct link here), shows city lights from San Juan and Ponce on the northeast and southwest shores, respectively, shining through relatively thick clouds to the southeast of the eye of the storm.

Annotated Imagery from Suomi NPP (VIIRS Day Night Band Visible (0.7 µm) Imagery and Infrared (11.45 µm) courtesy of William Straka) are shown below.

Suomi NPP Day Night Band Visible (0.7 µm) Imagery, 0554 UTC on 21 September 2017 (Click to enlarge)

Suomi NPP VIIRS Infrared (11.45 µm) Imagery, 0554 UTC on 21 September 2017 (Click to enlarge)

Hurricane Maria makes landfall in Puerto Rico

September 20th, 2017 |

GOES-16 Visible Imagery (0.64 µm), 1017-1117 UTC, at 30-second time steps, on 20 September 2017 (Click to animate)

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

Strong Category 4 Hurricane Maria has made landfall in Puerto Rico. According to the National Hurricane Center, landfall occurred around 1035 UTC near Yabacuo on Puerto Rico’s southeast coast. The GOES-16 30-second (using overlapping mesoscale sectors) Visible Animation, above, shows the storm as it made landfall. Maria had recently completed an Eyewall Replacement Cycle as it made landfall. The animation below, using morphed microwave imagery (from this site), shows the development of an outer eyewall and subsequent erosion of the inner eyewall during the 24 hours prior to landfall.

Morphed Microwave Imagery centered on Hurricane Maria for the 24 hours prior to landfall in Puerto Rico (Click to enlarge)

GOES-16 Clean Window Infrared (10.3 µm) Imagery shows a distinct eye as the storm makes landfall. Subsequently, however, the eye filled in as it moved over the mountainous interior of Puerto Rico.

GOES-16 Infrared (10.3 µm) Imagery, 0957-1136 UTC on 20 September 2017 (Click to animate)

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images (Click to play MP4 animation)

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images (Click to play MP4 animation)

A 2-panel comparison of GOES-16 Visible (0.64 µm) and Infrared Window (10.3 µm) imagery during the 1020-1620 UTC time period is shown above. It can be seen that deep eyewall convection moved over much of the island as Maria made its journey across Puerto Rico.

Suomi NPP flew over Maria early in the morning on 20 September, when the storm was near St. Croix. The toggle below shows the 11.45 µm Infrared image from VIIRS and the Day Night Band Visible (0.7 µm) Imagery. The Moon on 20 September was a New Moon, so no lunar illumination was present for the Day Night Band. The eye of the storm was nevertheless apparent in the image.  A zoomed-in Infrared image over the eye is here.

Suomi NPP VIIRS 11.45 µm Infrared image from VIIRS and the Day Night Band Visible (0.7 µm) Imager, 0613 UTC on 20 September 2017 (Click to enlarge)

Suomi NPP overflew Maria again when the storm was moving offshore from Puerto Rico, and a toggle (Visible and Infrared) below shows the storm at 1724 UTC on 20 September. Click here for a zoomed-in image (Visible) over the eye.

Suomi NPP VIIRS 11.45 µm Infrared image from VIIRS and Visible (0.64 µm) Image, 1724 UTC on 20 September 2017 (Click to enlarge)

More information on Maria is available at the National Hurricane Center and at the CIMSS Tropical Weather Website.