Ex-typhoon Merbok enters the Bering Sea

September 16th, 2022 |

GOES-17 Air Mass RGB images, with hourly plots of surface reports [click to play animated GIF | MP4]

GOES-17 (GOES-West) Air Mass RGB images with hourly plots of surface reports (above) showed the remnants of ex-Typhoon Merbok (storm track) moving northward across the Bering Sea (surface analyses) on 16 September 2022. This strong extratropical cyclone had an anomalously-low surface pressure as it moved northward — in fact, its central Mean Sea Level Pressure set a record for the month of September in the Bering Sea:

The storm center passed just northwest of Buoy 46035, where the peak wind gust was 68 knots (78 mph) at 1800 UTC and 1900 UTC on 16 September. These strong winds caused wave heights to 52 feet, which resulted in a notable upwelling of cooler water. Such strong southwesterly surface winds in the vicinity of Buoy 46035 occurred beneath a swath of anomalously-strong 925 hPa winds within the southeast quadrant of the storm. Two particularly adverse impacts of these strong winds were coastal erosion and flooding across much of western Alaska (more of the storm’s impacts are discussed here).

In the Air Mass RGB images, deeper shades of red-to-orange in the vicinity of the storm center vhighlighted areas where there was enhanced ozone within the atmospheric column (due to an anomalously-low tropopause ) — overlays of AK-NAM40 model Potential Vorticity (PV) 1.5 pressure (below) indicated that the “dynamic tropopause” near the storm center may have descended as low as the 900 Pa pressure level.

GOES-17 Air Mass RGB images, with overlays of AK-NAM40 model PV1.5 pressure [click to play animated GIF | MP4]

In a larger-scale view of GOES-17 Air Mass RGB images created using Geo2Grid (below), one interesting feature was a distinct plume of moist tropical air (highlighted by darker shades of green) that moved northward across the Aleutian Islands into the Bering Sea (for example, at 0600 UTC on 16 September in the warm sector of the storm).

GOES-17 Air Mass RGB images [click to play animated GIF | MP4]

The MIMIC Total Precipitable Water product (below) showed the north-northeastward transport of tropical moisture as Typhoon Merbok transitioned to an extratropical storm.

MIMIC Total Precipitable Water product [click to play animated GIF | MP4]

Additional information pertaining to this event is available here

Using NUCAPS profiles before Pyrocumulus events

September 11th, 2022 |
GOES-17 True-color imagery, 2101 UTC 10 September to 0106 UTC on 11 September

A CSPP Geosphere mp4 animation from late on 10 September, above (link), shows the development of a pyrocumulus cloud at the south edge of the Cedar Creek fire complex in Oregon (previously discussed here, here and here). The animation above starts at 2101 UTC, shortly after a NOAA-20 overpass above the region. NUCAPS profiles over the regions can define the thermodynamics to help forecasters determine is pyrocumulus clouds might develop. The Green points in the sounding availability plots, below, denote retrievals that converged to a solution using both microwave and infrared data from the ATMS and CrIS instruments, respectively. This includes the profiles near the very warm Cedar Creek fire pixels in east-central Oregon. (Here is a zoomed-in view over the fire with GOES-17 FDCA Fire Power observations; note the two different regions of active fire).

GOES-17 Band 7 (3.9 µm) imagery at 2020 UTC on 10 September 2022 along with NUCAPS Sounding Availability plots (Click to enlarge)

The animation below steps through 3 NUCAPS profiles near the fire. A dry atmosphere is apparent, but note also the very steep lapse rates. If convection develops, aided by the heat of the fire, there is little to inhibit its growth to the tropopause.

NUCAPS profiles east, over and west of the Cedar Creek fire, ca. 2050 UTC on 10 September 2022 (Click to enlarge)

NUCAPS profiles can be gridded to provide horizontal fields of thermodynamic variables. The lapse rate computed from 850 and 500 mb temperatures, below, also shows very steep lapse rates (note that portions of Oregon are at/above 850 mb and no data are available).

GOES-17 Band 7 (3.9 µm) imagery along with NUCAPS gridded lapse rates (850-500 mb), ca. 2030 UTC on 10 September 2022 (Click to enlarge)

One things that happens when a Pyrocumulus develops: the cloud is trackable (in contrast to any surrounding smoke). The CSPP Geosphere animation below (link) shows the Night Microphysics (at night) and True-Color (during the day) — the cloud can be tracked until is dissipates near dawn, and the true-color imagery the next day shows the smoke associated with the pyrocumulus has also moved to the east. Note also in the animation how the active fires show up in the GOES-17 Night Microphysics as different shades of magenta.

Hourly imagery from CSPP Geosphere, 2206 10 September 2022 – 1706 UTC on 11 September 2022

Although infrared imagery is challenged to view smoke at night, as suggested in the animation above, the VIIRS Day Night band sees it (if there is sufficient illumination by the Moon). That was the case early on 11 September, as shown below (in an image taken from the VIIRS Today website). Both the light signature from fires are apparent as is the smoke plume from the pyrocumulus.

NOAA-20 Day Night Band visible (0.7 µm) imagery over Oregon, ca. 1100 UTC on 11 September 2022 (click to enlarge)

AWIPS Satellite imagery in this blog post were created using the TOWR-S AWIPS. Thank you!

Pyrocumulonimbus clouds in Oregon, Idaho and California

September 10th, 2022 |

An extended period of hot temperatures across much of the western US — where drought conditions were widespread — helped set the stage for large wildfires which produced several pyrocumulonimbus (pyroCb) clouds in parts of Oregon, Idaho and California during the 07-10 September 2022 period.

===== 07 September =====

GOES-18 Day Land Cloud Fire RGB images [click to play animated GIF | MP4]

GOES-18 (GOES-West) Day Land Cloud Fire RGB images (above) displayed numerous wildfires (clusters of red pixels) from far eastern Oregon into Idaho on 07 September 2022. Three of the larger fires — one in Oregon and two in Idaho — produced one or more pulses of pyroCb clouds during the day.

1-minute GOES-18 True Color RGB images visualized using CSPP GeoSphere (below) showed the smoke-laden cloud tops (shades of tan) associated with some of the pyroCb pulses from the eastern Oregon and central Idaho wildfires.

GOES-18 True Color RGB images [click to play MP4 animation]

4-panel displays of 1-minute Mesoscale Domain Sector GOES-18 Day Land Cloud Fire RGB, Shortwave Infrared (3.9µm), “Clean” Infrared Window (10.35 µm) and Cloud Top Temperature (below) provided a closer view of a vigorous pyroCb produced by the Moose Fire in far eastern Idaho (near the Montana border). During that time period, the maximum surface 3.9 µm infrared brightness temperature of the fire signature reached 137.88oC (the saturation temperature of GOES-18 ABI Band 7 detectors). The coldest pyroCb cloud-top 10.35 µm infrared brightness temperatures were -52oC, while the coldest Cloud Top Temperature derived product values were around -56oC.

GOES-18 Day Land Cloud Fire RGB (top left), Shortwave Infrared (3.9 µm, top right), Infrared Window (10.35 µm, bottom left) and Cloud Top Temperature (bottom right) [click to play animated GIF | MP4]

===== 08 September =====

GOES-17 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle) and “Clean” Infrared Window (10.35 µm, bottom) [click to play animated GIF | MP4]

1-minute GOES-17 (which resumed duty as GOES-West as of 1601 UTC on 08 September) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed a “marginal” pyroCb produced by the Mosquito Fire in California on 08 September 2022, whose coldest cloud-top 10.35 µm infrared brightness temperature reached -39oC (just shy of the -40oC threshold of pyroCb classification) — however, the Cloud Top Temperature derived product (not shown) did reach -42oC.

1-minute GOES-17 True Color RGB images (below) displayed the smoke-laden (shades of tan) cloud top of this “marginal pyroCb”.

GOES-17 True Color RGB images [click to play MP4 animation]

===== 10 September =====

As discussed in this blog post, the Cedar Creek Fire in Oregon had been producing a large smoke plume during the day on 09 September — and this trend continued into the overnight hours, as shown by a Suomi-NPP VIIRS Day/Night Band (0.7 µm) image valid at 1020 UTC on 10 September (below). Ample illumination by a Full Moon provided an excellent example of the “visible image at night” capability of the Day/Night Band (DNB).

Suomi-NPP VIIRS Day/Night Band (0.7 µm) image, valid at 1020 UTC on 10 September [click to enlarge]

In a closer view of of the Cedar Creek Fire, a toggle between the corresponding Suomi-NPP VIIRS DNB and Shortwave Infrared images (below) displayed the bright nighttime glow of the more active individual fires (as well as the dense smoke plume drifting northwestward) in the DNB image — and the thermal signature of fires along the northwestern perimeter was evident in the Shortwave Infrared image, even though the dense smoke plume was overhead.

Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (11.45 µm) images, valid at 1020 UTC on 10 September [click to enlarge]

During the subsequent daytime hours, a sequence of 1-minute GOES-17 Day Land Cloud Fire RGB, Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.35 µm) and Cloud Top Temperature product (below) showed that the Cedar Creek Fire produced a pyroCb cloud late in the day on 10 September 2022. During that particular time period, the maximum surface 3.9 µm infrared brightness temperature of the fire signature reached 138.71oC (the saturation temperature of GOES-17 ABI Band 7 detectors). The coldest cloud-top 10.35 µm infrared brightness temperature was -45oC, while the coldest Cloud Top Temperature derived product value was -49oC.

Sequence of GOES-17 Day Land Cloud Fire RGB, Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.35 µm) and Cloud Top Temperature product [click to play animated GIF | MP4]

1-minute GOES-17 True Color RGB images (below) showed the Cedar Creek Fire pyroCb rising through and towering above the large pall of lower-altitude smoke.

GOES-17 True Color RGB images [click to play MP4 animation]

During the following overnight hours, a toggle between Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (11.45 µm) images valid at 1002 UTC (below) revealed that the nighttime glow and thermal signature of larger active fires along the perimeter of the Cedar Creek Fire were still apparent, in spite of dense smoke that lingered over the area and high clouds that were beginning to move overhead from the west.

Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (11.45 µm) images, valid at 1002 UTC on 11 September [click to enlarge]

CSPP Geosphere views of smoke in Oregon and Idaho

September 9th, 2022 |
GOES-West True-Color imagery, 1506-1911 UTC on 9 September 2022

CSPP Geosphere animations from GOES-West (above, link) and GOES-East (below, link) both show an active fire — the Cedar Creek fire — over Oregon (previously discussed here). Low-level winds (as shown in the 1200 UTC sounding from Medford OR) are moving the smoke plume out over the Pacific Ocean. The oblique side-view from GOES-East (below) gives a better view of the structure of the smoke plume.

CSPP Geosphere GOES-East view over Oregon, 1506 – 1911 UTC on 9 September 2022

Later in the day, a brief pyrocumulus jump ejected smoke to higher altitudes, where westerly winds prevailed:

Fires over Idaho are also producing smoke that has been trapped in valleys, as shown below. Much of Idaho is under an Air Quality Alert (link). A current map of Air Quality can be viewed here. The image from 2000 UTC on 9 September is here.

GOES-West True-Color image from CSPP Geosphere, 1506 UTC on 9 September 2022 (Click to enlarge)