Anomalous cutoff low over the Beaufort Sea

June 12th, 2019 |

GOES-17 Mid-leve Water Vapor (6.9 µm, top) and GOES-15 Water Vapor (6.5 µm. bottom) imagess [click to play animation | MP4]

GOES-17 Mid-level Water Vapor (6.9 µm, top) and GOES-15 Water Vapor (6.5 µm. bottom) images [click to play animation | MP4]

A comparison of Water Vapor images from GOES-17 (GOES-West) and GOES-15 Water Vapor images (above) showed the signature of an anomalously-deep closed low that was moving southeastward over the Beaufort Sea north of Alaska during the 11 June – 12 June 2019 period. The images are shown in the native projection of each satellite — GOES-17 is positioned over the Equator at 137.2º W longitude, while GOES-15 is located at 128º W. The improved GOES-17 spatial resolution (2 km at nadir, vs 4 km for GOES-15) and more frequent imaging (every 10 minutes, vs every 30 minutes for GOES-15) allowed for a better depiction of this cutoff low — including smaller-scale features near the center of the broad circulation.

GFS model 500 hPa geopotential height, wind, and standardized height anomaly (source) analyses at 6- hour intervals (below) indicated 500 hPa geopotential height anomaly values reached -3 to -4 sigma (lighter shade of violet) for this cutoff low.

6-hourly GFS 500 hPa geopotential height, wind, and standardized height anomaly [click to enlarge]

6-hourly GFS 500 hPa geopotential height, wind, and standardized height anomaly [click to enlarge]

30-second GOES-17 images over Oregon/Idaho/Nevada

May 29th, 2019 |

GOES-17 “Red” Visible (0.64 µm) images, with hourly plots of surface reports [click to play MP4 animation]

GOES-17 “Red” Visible (0.64 µm) images, with hourly plots of surface reports [click to play MP4 animation]

Due to an overlap of GOES-17 (GOES-West) Mesoscale Domain Sectors, images were available at 30-second intervals — and “Red” Visible (0.64 µm) images (above) showed the development of thunderstorms over southeastern Oregon, southwestern Idaho and northern Nevada on 29 May 2019. Some of these thunderstorms produced heavy rainfall and small hail in southwestern Idaho, and a cold air funnel was spotted in northern Nevada (local storm reports).

A comparison of Visible images from GOES-17 and GOES-15 images (below) helps to underscore some of the improvements in the GOES-R series of satellites over their predecessors — with images every 30 seconds compared to every 4-15 minutes (with gaps of 30 minutes during the Full Disk scans every 3 hours), the short-term convective trends could be better monitored using GOES-17. Also note that the GOES-15 Visible images do not appear as bright as those from GOES-17 — prior to the GOES-R Series of satellites, the performance of visible detectors degraded over time, leading to imagery that appeared more dim as the Imager instrument aged. Visible detectors on the new ABI instrument benefit from on-orbit calibration to remedy this type of degradation.

GOES-17 “Red” Visible (0.64 µm, left) and GOES-15 Visible (0.63 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

GOES-17 “Red” Visible (0.64 µm, left) and GOES-15 Visible (0.63 µm, right) images, with hourly plots of surface reports; images are displayed in the native projection of each satellite [click to play MP4 animation]

Stationary linear boundary over the Pacific Ocean

May 2nd, 2019 |

GOES-17 Low-level Water Vapor (7.3 µm), Mid-level Water Vapor (6.9 µm), Upper-level Water Vapor (6.2 µm) and

GOES-17 Low-level Water Vapor (7.3 µm), Mid-level Water Vapor (6.9 µm), Upper-level Water Vapor (6.2 µm) and “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

In a comparison of GOES-17 (GOES-West) Low-level Water Vapor (7.3 µm), Mid-level Water Vapor (6.9 µm), Upper-level Water Vapor (6.2 µm) and “Clean” Infrared Window (10.3 µm) images (above), the Water Vapor imagery revealed an interesting stationary linear boundary — oriented NNW to SSE, near 152-154ºW longitude — over the North Pacific Ocean on 02 May 2019. In addition, note the other linear boundary that propagated from E to W, moving right through the aforementioned stationary boundary (best seen in the 6.19 um Upper-level Water Vapor imagery). There was no evidence of either of these linear features in the corresponding GOES-17 Infrared imagery, or in Visible imagery (not shown). A perfect candidate for the “What the heck is this?” blog category.

One possible explanation for the curious stationary feature was that it resulted from a convergence of flow around the cutoff low to the east and a digging trough approaching from the west. GOES-15 Infrared cloud-tracked Derived Motion Winds from the CIMSS Tropical Cyclones site (below) did show evidence of some converging flow in that region. Derived Motion Winds from GOES-17 were still in the Beta stage, and were not available for display in AWIPS.

GOES-15 Infrared cloud-tracked Derived Motion Winds [click to enlarge]

GOES-15 Infrared cloud-tracked Derived Motion Winds [click to enlarge]

Wildfire in Alaska

May 1st, 2019 |

GOES-17 Shortwave Infrared (3.9 µm) and "Red" Visible (0.64 µm) images [click to play animation | MP4]

GOES-17 Shortwave Infrared (3.9 µm) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

On 01 May, GOES-17 (GOES-West) Shortwave Infrared (3.9 µm) and “Red” Visible (0.64 µm) images (above) showed the thermal anomaly (or fire “hot spot”) and dispersion of smoke from the first moderate-size wildfire of 2019 in the Interior of Alaska — the Oregon Lakes Impact Area Fire about 7 miles southwest of Fort Greely. This fire grew from 30 acres to 4000 acres in a 24-hour period, aided by warm daytime temperatures with low relative humidity values and southwest winds late in the day on 30 April (surface data). The Oregon Lakes Impact Area Fire was burning in a remote area just west of the Delta River which was previously burned by the 2013 Mississippi Fire; that area also contained unexploded ordnance dropped by military aircraft during training exercises.

A toggle between Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images at 1216 UTC or 4:16 am local time (below) revealed the nighttime glow of the fire, along with a more accurate depiction of the size and location of the thermal anomaly.

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

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

Although the color enhancements were different, a comparison of Shortwave Infrared images from Suomi NPP (3.74 µm) at 1216 UTC and GOES-17 (3.9 µm) at 1220 UTC (below) demonstrated the advantage of imagery from polar-orbiting satellites at high latitudes. In this example, the 375-meter resolution VIIRS image showed 2 distinct fire hot spots that were not apparent in the lower spatial resolution — 2 km at nadir, decreasing to about 4 km over Alaska — GOES-17 image.

Shortwave Infrared images from Suomi NPP (3.74 µm) and GOES-17 (3.9 µm) [click to enlarge]

Shortwave Infrared images from Suomi NPP (3.74 µm) and GOES-17 (3.9 µm) [click to enlarge]

A larger-scale view of GOES-17 Shortwave Infrared and Visible images from 02-04 UTC on 02 May (below) showed the fire as it exhibited its peak 3.9 µm infrared brightness temperature (51.3ºC or 324.5 K at 0210 UTC) and the smoke plume had drifted over 100 miles to the southeast, moving over Beaver Creek, Yukon (CYXQ). While most of the smoke was apparently lofted above the boundary layer, the surface visibility at Fort Greely PABI was briefly reduced to 6 miles at 09 UTC or 1am local time on 02 May. Note the lack of “false cold pixels” adjacent to the warmest 3.9 µm pixels — this is due to a recent change to the GOES-R ABI Band 7 resampler, as detailed in this blog post.

GOES-17 Shortwave Infrared (3.9 µm) and "Red" Visible (0.64 µm) images [click to play animation | MP4]

GOES-17 Shortwave Infrared (3.9 µm) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

A comparison of Visible and Shortwave Infrared images from GOES-17 and GOES-15 (below) highlighted the improved fire detection and monitoring capability of the new GOES-R series. The higher spatial resolution (0.5 km vs 1.0 km at nadir for Visible, and 2 km vs 4 km at nadir for Shortwave Infrared) and more frequent image scans (10 minutes for GOES-17 Full Disk vs 15-30 minutes for GOES-15 CONUS sector) along with better Image Navigation and Registration (INR) were especially valuable at the higher latitudes of Alaska. For example, the subtle behavior of the fire’s smoke column vertical jump at 2350 UTC was only apparent in the GOES-17 Visible imagery.

GOES-17 Visible (0.64 µm, top left), GOES-15 Visible (0.63 µm, top right), GOES-17 Shortwave Infrared (3.9 µm, bottom left) and GOES-15 Shortwave Infrared (3.9 µm, bottom right) images [click to play animation | MP4]

GOES-17 Visible (0.64 µm, top left), GOES-15 Visible (0.63 µm, top right), GOES-17 Shortwave Infrared (3.9 µm, bottom left) and GOES-15 Shortwave Infrared (3.9 µm, bottom right) images [click to play animation | MP4]

Since the fire was also located within the GOES-17 Mesoscale Domain Sector #2, 1-minute imagery provided an even better depiction of the fire’s smoke column vertical jump and downstream smoke transport (below).

GOES-17 Visible (0.64 µm, top left), GOES-15 Visible (0.63 µm, top right), GOES-17 Shortwave Infrared (3.9 µm, bottom left) and GOES-15 Shortwave Infrared (3.9 µm, bottom right) images [click to play animation | MP4]

GOES-17 Visible (0.64 µm, top left), GOES-15 Visible (0.63 µm, top right), GOES-17 Shortwave Infrared (3.9 µm, bottom left) and GOES-15 Shortwave Infrared (3.9 µm, bottom right) images [click to play animation | MP4]