Moderate to severe turbulence aloft near the International Date Line

December 14th, 2016 |

Himawari-8 Water Vapor (6.2 µm) images, with pilot reports of turbulence [click to play animation]

Himawari-8 Water Vapor (6.2 µm) images, with pilot reports of turbulence [click to play animation]

Himawari-8 Water Vapor (6.2 µm) images (above; also available as MP4 and McIDAS-V animations) revealed the presence of a subtle packet of upper-tropospheric gravity waves propagating southeastward near the International Date Line (180º longitude over the central Pacific Ocean), just to the west/southwest of Midway Atoll on 14 December 2016 — and there were a few pilot reports of moderate to severe turbulence (which were responsible for at least one injury) in the general vicinity of this gravity wave feature from 1530 to 1740 UTC, at altitudes of 35,000 to 38,000 feet:

PHNL UUA /OV 2800N 18000W/TM 1530/FL380/TP B767/TB MOD-SEV/RM ZOA CWSU
PHNL UUA /OV 2643N 17757W/TM 1732/FL350/TP A330/TB SEV/RM ZOA CWSU
PHNL UUA /OV 2626N 17917W/TM 1740/FL360/TP B747/TB SEV/RM ZOA CWSU

A larger-scale view using all 3 water vapor bands of the AHI instrument on the Himawari-8/9 satellites (below; also available as an MP4 animation) showed that a broad trough was moving eastward away from the International Date Line, with the signature of a jet streak diving southward toward the region of the turbulence reports (Note: the ABI instrument on the GOES-R series of satellites will feature these same 3 upper level, mid-level and lower level water vapor bands).

Himawari-8 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.4 µm, bottom) images [click to play animation]

Himawari-8 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.4 µm, bottom) images [click to play animation]

GFS model 250 hPa analyses (12 UTC | 18 UTC | source) confirmed that the region of turbulence reports was located within the exit region an approaching 50-70 m/s or 97-136 knot upper tropospheric jet, where convergence (red contours) was maximized.


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Similarly, Himawari-8 water vapor image Derived Motion Winds, below, also indicated increasing upper-tropospheric convergence along the International Date Line (180º longitude) between 25º and 30º N latitude from 12 UTC to 18 UTC (below; source).

Himawari-8 water vapor image Derived Motion Winds at 12 UTC, with corresponding contours of Upper-tropospheric divvergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 12 UTC, with corresponding contours of Upper-tropospheric divvergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 15 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 15 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 18 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 18 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

A comparison of 2-km resolution Himawari-8 and 4-km resolution GOES-15 Water Vapor images (below; also available as an MP4 animation) showed that the gravity wave feature was not readily apparent on the lower spatial resolution GOES-15 images (which were only available every 30 minutes, in contrast to every 10 minutes from Himawari-8). The same color enhancement is applied to both sets of images — but because of differences between the Himawari-8 vs GOES-15 water vapor band characteristics (namely the central wavelength and the spectral response function, but also the water vapor weighting function profiles as influenced by the dissimilar satellite viewing angles) the resulting water vapor images differ in their general appearance.

Himawari-8 Water Vapor (6.2 µm, left) and GOES-15 Water Vapor (6.5 µm, right) images, with pilot reports of turbulence [click to play animation]

Himawari-8 Water Vapor (6.2 µm, left) and GOES-15 Water Vapor (6.5 µm, right) images, with pilot reports of turbulence [click to play animation]

This case demonstrated well the importance of viewing all 11 bits of information contained in the Himawari-8 Imagery. The animation at the top of the Blog Post shows an 8-bit display; a similar 8-bit display that uses a different color enhancement is here, courtesy of Dan Lindsey at CIRA. All 8-bit displays are limited to 256 different colors. The image below compares 8-bit (McIDAS-X on the left) and 11-bit (McIDAS-V on the right) displays at 1530 UTC.

Himawari-8 Water Vapor (6.2 µm) image at 1530 UTC, as viewed using 8-bit McIDAS-X (left) and 11-bit McIDAS-V (right) displays [click to enlarge]

Himawari-8 Water Vapor (6.2 µm) image at 1530 UTC, as viewed using 8-bit McIDAS-X (left) and 11-bit McIDAS-V (right) displays [click to enlarge]

Here is a toggle from AWIPS that compares 11-bit and 8-bit displays. The feature causing the turbulence is quite subtle, and 11-bit displays (which allow 2048 different colors) are necessary to accurately show it.

 

Blizzard impacts North Dakota and Minnesota

December 8th, 2016 |

GOES-13 Water Vapor (6.5 µm) images, with hourly surface weather symbols [click to play animation]

GOES-13 Water Vapor (6.5 µm) images, with hourly surface weather symbols [click to play animation]

A major winter storm produced widespread blizzard conditions in North Dakota and northwestern Minnesota (as well as far northern South Dakota) as low pressure deepened (3-hourly surface analyses) while moving from South Dakota across Minnesota (and eventually over Ontario and western Quebec) during the 05 December08 December 2016 period. Storm total snowfall amounts included 16.0 inches in Montana, 19.0 inches in North Dakota and 13.9 inches in Minnesota; peak wind gusts were as high as 63 knots (72 mph) in South Dakota, 56 knots (64 mph) in North Dakota and 37 knots (43 mph) in Minnesota (KBIS PNS | KFGF PNS | WPC storm summary). In North Dakota, nearly the entire portion of both Interstates 94 and 29 were closed. The large size of the storm could be seen on GOES-13 (GOES-East) Water Vapor (6.5 µm) images (above).

A closer view using GOES-13 Water Vapor imagery with overlays of hourly reports of surface winds and wind gusts (below) showed that wind speeds remained strong enough to create travel-restricting blowing snow over eastern North Dakota and western Minnesota even into the early hours of 08 December (due to the continuing strong pressure gradient between the large low in Canada and the arctic high that was moving into Montana and Wyoming.

GOES-13 Water Vapor (6.5 µm) images, with hourly surface winds (yellow) and wind gusts in knots (red) [click to play animation]

GOES-13 Water Vapor (6.5 µm) images, with hourly surface winds (yellow) and wind gusts in knots (red) [click to play animation]

In the wake of the storm on 09 December, a southeastward flow of cold arctic air (with surface air temperatures in the 0 to -15º F range) over the still-unfrozen water of Lake Sakakawea (which exhibited MODIS Sea Surface Temperature values as warm as 37.9º F) caused lake effect cloud bands to form and extend downwind of the lake — these cloud bands were very evident in a comparison of 250-meter resolution Aqua MODIS true-color and false-color Red/Green/Blue (RGB) images from the MODIS Today site (below). In the false-color image, snow/ice appears as shades of cyan, in contrast to supercooled water droplet clouds which appear as shades of white. The 1.6 µm snow/ice band used to create the MODIS false-color image will also be available with the ABI instrument on the GOES-R series (beginning with GOES-16).

Aqua MODIS true-color and false-color RGB images [click to enlarge]

Aqua MODIS true-color and false-color RGB images [click to enlarge]

With a fresh, deep snow cover and cold arctic air in place, strong nocturnal radiational cooling allowed North Dakota to experience its first -30º F low temperatures of the season on the morning of 10 December. Aqua MODIS Land Surface Temperature values at 0939 UTC or 3:39 am local time (below) were as cold as -39º F (darker violet color enhancement) near the sites that reported the -30º F low temperatures.

Aqua MODIS Land Surface Temperature product [click to enlarge]

Aqua MODIS Land Surface Temperature product [click to enlarge]

Hurricane Force low in the North Pacific Ocean

November 17th, 2016 |

GOES-15 Water Vapor (6.5 µm) images, with hourly surface and buoy/ship reports [click to play MP4 animation]

GOES-15 Water Vapor (6.5 µm) images, with hourly surface and buoy/ship reports [click to play MP4 animation]

GOES-15 (GOES-West) Water Vapor (6.5 µm) images (above; also available as a 52 Mbyte animated GIF) showed the development of a Hurricane Force low in the North Pacific Ocean during the 15 November – 17 November 2016 period. Surface analysis charts for this storm, produced by the Ocean Prediction Center, are shown below.

Surface analyses from 12 UTC on 15 November to 12 UTC on 17 November

Surface analyses from 12 UTC on 15 November to 12 UTC on 17 November

Although it was more of an oblique viewing angle, JMA Himawari-8 AHI Water Vapor (6.2 µm, 6,9 µm and 7.3 µm) images (below; also available as a 27 Mbyte animated GIF) provided a nice view of the storm on 15 November as it was intensifying to produce Hurricane Force winds.

JMA Hmawari-8 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.3 µm, bottom) images [click to play MP4 animation]

JMA Hmawari-8 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.3 µm, bottom) images [click to play MP4 animation]

Since the ABI instrument on GOES-R is nearly identical to the AHI, there will also be imagery from 3 water vapor bands (6.2 µm, 6.9 µm and 7.3 µm) available once GOES-R becomes operational (as GOES-16) in 2017.

 

Fires continue in the southeast United States

November 14th, 2016 |

Terra MODIS (1650 UTC), Aqua MODIS (1829 UTC) and Suomi NPP VIIRS (1913 UTC) true-color images [click to enlarge]

Terra MODIS (1650 UTC), Aqua MODIS (1829 UTC) and Suomi NPP VIIRS (1913 UTC) true-color images [click to enlarge]

Fires (as seen on 07 and 10 November) continued to burn in parts of the southeast US on 14 November 2016. A sequence of 3 consecutive true-color Red/Green/Blue (RGB) images from Terra MODIS (1650 UTC), Aqua MODIS (1829 UTC) and Suomi NPP VIIRS (1913 UTC) viewed using RealEarth, above, showed the aerial extent of the dense smoke that was most concentrated over Tennessee, Georgia, North Carolina and South Carolina. With the aid of some of the 16 spectral bands on the ABI instrument aboard GOES-R, true-color images like these will be available at least once every 5 minutes over the Lower 48 states and adjacent areas.

GOES-13 (GOES-East) Visible (0.63 µm) images with plots of surface weather and visibility (below; also available as an MP4 animation) revealed that visibility was restricted to 3 miles or less at one or more sites in all of the aforementioned states. A pair of pilot reports in eastern Tennessee indicated that he top of the smoke layer was at 6000 feet above ground level.

GOES-13 Visible (0.63 µm) images, with hourly plots of surface weather (yellow) and visibility (statute miles, in cyan) [click to animate]

GOES-13 Visible (0.63 µm) images, with hourly plots of surface weather (yellow) and visibility (statute miles, in cyan) [click to animate]

High loading of particulate matter (PM) due to smoke led to AIRNow Air Quality Index ratings of Unhealthy (red)  to Very Unhealthy (purple) over much of that 4-state region (below).

Hourly AIRNow Particulate Matter (PM) Air Quality Index (AQI)

Hourly AIRNow Particulate Matter (PM) Air Quality Index (AQI)

===== 15 November Update =====

Suomi NPP VIIRS Shortwave Infrared (3.74 um) and Day/Night Band (0.7 um) images, plus METAR surface reports [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 um) and Day/Night Band (0.7 um) images, plus METAR surface reports [click to enlarge]

A toggle between Suomi NPP VIIRS Shortwave Infrared (3.74 um) and Day/Night Band (0.7 um) images (with and without METAR surface reports) at 0735 UTC or 3:35 am local time on 15 November (above) showed the “hot spot” signatures and bright glow from the larger fires that were burning in northern Georgia and western North Carolina. With ample illumination from the Moon — which was in the Waning Gibbous phase, at 99% of Full — smoke plumes from some of these fires could be seen drifting southward or southeastward,  thanks to the “visible image at night” capability of the Day/Night Band.

During the subsequent daytime hours, Terra MODIS and Suomi NPP VIIRS true-color RGB images (below) again revealed the vast coverage of the thick smoke — and VIIRS Aerosol Optical Depth values were quite high over South Carolina. Unhealthy AQI values persisted during much of the day across parts of Tennessee, Georgia and South Carolina.

Terra MODIS and Suomi NPP VIIRS true-color images, with VIIRS Aerosol Optical Depth (click to enlarge]

Terra MODIS and Suomi NPP VIIRS true-color images, with VIIRS Aerosol Optical Depth (click to enlarge]

A sampling of pilot reports (PIREPS) showed some of the impacts that the smoke was having on aviation (below).

Suomi NPP VIIRS Visible (0.64 µm) image with a PIREP over South Carolina [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) image with a PIREP over South Carolina [click to enlarge]

Aqua MODIS Visible (0.65 µm) image with a PIREP over Georgia [click to enlarge]

Aqua MODIS Visible (0.65 µm) image with a PIREP over Georgia [click to enlarge]

GOES-13 Visible (0.63 µm) image with a PIREP over North Carolina [click to enlarge]

GOES-13 Visible (0.63 µm) image with a PIREP over North Carolina [click to enlarge]

===== 16 November Update =====

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

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

Terra/Aqua MODIS and Suomi NPP VIIRS true-color images (above) showed that much of the smoke had moved over the adjacent offshore waters of the Atlantic Ocean on 16 November.