Severe turbulence over Hawai’i

January 12th, 2018 |

GOES-15 Water Vapor (6.5 µm) images, with hourly pilot reports of turbulence [click to play animation]

GOES-15 Water Vapor (6.5 µm) images, with hourly pilot reports of turbulence [click to play animation]

Numerous pilot reports of moderate to severe turbulence were received over the Hawai’i area on 12 January 2018 — and GOES-15 (GOES-West) Water Vapor (6.5 µm) images (above; also available as an MP4) showed the development of a quasi-stationary gravity wave train over the northwestern portion of the island chain which appeared to be associated with many of these pilot reports.

HNL UA /OV 2115N16010W/TM 2241/FL320/TP B767/TB CONT MOD TURB

HNL UUA /OV 2115N16048W/TM 2255/FL340/TP H/B747/TB MOD-SEV TURB

HNL UUA /OV BOARD/TM 2350/FL370/TP H/B772/TB SEVERE TURB

PHNL UUA /OV 2443N 15516W /TM 2358 /FL370 /TP B737 /TB SEV 370 /RM ZOA CWSU AWC-WEB

In spite of the large satellite viewing angle, these waves were also very evident on Himawari-8 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below; also available as an MP4). The 3 Water Vapor bands on the Himawari AHI are nearly identical to the 3 Water Vapor bands on the GOES-R series ABI.

Himawari-8 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and 6.2 µm, right) Water Vapor images, with hourly pilot reports of turbulence [click to play animation]

Himawari-8 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images, with hourly pilot reports of turbulence [click to play animation]

A toggle between 1-km resolution Terra MODIS Water Vapor (6.7 µm), Infrared Window (11.0 µm) and 250-meter resolution true-color Red-Green-Blue RGB images at 2106 UTC on 12 January (below) showed that no high-altitude clouds were associated with the gravity wave features — thus, these aircraft encounters were examples of Clear Air Turbulence (CAT).

Terra MODIS Water Vapor (6.7 µm) and True-color RGB images [click to enlarge]

Terra MODIS Water Vapor (6.7 µm), Infrared Window (11.0 µm) and true-color RGB images [click to enlarge]

A color-enhanced version of the Aqua MODIS Water Vapor (6.7 µm) image at 0014 UTC on 13 January is shown below (courtesy of Jordan Gerth, CIMSS).

An AWIPS screen capture (below, courtesy of Robert Bohlin, NWS Honolulu and Jordan Gerth, CIMSS) displays a High Pass filter product along with the 3 individual Himawari-8 Water Vapor band images at 0120 UTC on 13 January.

Upper-level Water Vapor (6.2 µm, upper right), Mid-level Water Vapor (6.9 µm, lower left) and Lower-level Water Vapor (7.3 µm, lower right) images [click to enlarge]

Himawari-8 High Pass filter product (6.9 µm, upper left), Upper-level Water Vapor (6.2 µm, upper right), Mid-level Water Vapor (6.9 µm, lower left) and Lower-level Water Vapor (7.3 µm, lower right) images [click to enlarge]

It bears mention that the rawinsonde data from Lihue, Hawai’i at 0000 UTC on 13 January (below) indicated significant wind shear (both speed and directional) within the 200-300 hPa layer (text listing) — the layer in which many of the turbulence reports were found.

Rawinsonde data from Lihue, Hawai'i at 00 UTC on 13 January [click to enlarge]

Rawinsonde data from Lihue, Hawai’i at 00 UTC on 13 January [click to enlarge]

The packet of gravity waves was directly over Lihue (red asterisk) at that time (below).

GOES-15 Water Vapor (6.5 µm) image at 0000 UTC on 13 January, with pilot reports of turbulence plotted. The red asterisk denotes the location of Lihue [click to enlarge]

GOES-15 Water Vapor (6.5 µm) image at 0000 UTC on 13 January, with pilot reports of turbulence plotted. The red asterisk denotes the location of Lihue [click to enlarge]

Ice floes in Chesapeake Bay

January 7th, 2018 |

Landsat-8 false-color RGB image [click to enlarge]

Landsat-8 false-color RGB image [click to enlarge]

In the wake of the explosive cyclogenesis off the East Coast of the US on 04 January 2018, very cold air began to spread across much of the eastern half of the Lower 48 states. Focusing on the Hampton Roads area of southeastern Virginia, satellite imagery began to show the formation of ice in the rivers and bays. On 06 January, a 30-meter resolution Landsat-8 false-color Red-Green-Blue (RGB) image viewed using RealEarth (above) revealed some of this ice — in particular, long narrow ice floes (snow and ice appear as shades of cyan) that likely emerged from the Back River (northeast of Hampton) and were drifting northward and southward just off the coast of the Virginia Peninsula.

On the following day (07 January), 250-meter resolution Terra MODIS true-color and false-color RGB images from the MODIS Today site (below) showed that a larger V-shaped ice floe was located just southeast of the Peninsula, with its vertex pointed toward the Hampton Roads Bridge-Tunnel (HRBT). Snow and ice also appear as shades of cyan in the MODIS false-color image.

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

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

07 January also happened to be the last full day of imagery to be broadcast by the GOES-13 satellite — a comparison of 1-minute Mesoscale Sector GOES-16 (GOES-East) Visible (0.64 µm) and 15-30 minute interval GOES-13 Visible (0.63 µm) images (below) showed that the V-shaped ice floe continued to drift southwestward toward the HRBT. However, it was difficult to tell whether the ice feature made it over and past the tunnel; even with the improved GOES-16 Visible spatial resolution (0.5 km at satellite sub-point, compared to 1.0 km for GOES-13) and the 1-minute rapid image scans, the ice floe became harder to track during the afternoon hours before high clouds began to overspread the region.

"GOES-16

GOES-16 Visible (0.64 µm, left) and GOES-13 Visible (0.63 µm, right) images, with hourly surface air temperatures (ºF) plotted in yellow [click to play MP4 animation]

However, a close examination of Suomi NPP VIIRS true-color and false-color images at 1826 UTC (below) indicated that some of the ice had indeed moved westward past Fort Monroe (on the far southeastern tip of the Peninsula) and over/past the HRBT.

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]

On the topic of cold temperatures in southeastern Virginia, a new daily record low of -3 ºF was set at Richmond on the morning of 07 January, and at Norfolk new daily record low and record low maximum temperatures were set (10 ºF and 23 ºF, respectively).

Satellite signatures of a “sting jet”

January 4th, 2018 |

GOES-16 Lower-level (7.3 µm) images, with hourly plots of buoy and ship reports [click to play MP4 animation]

GOES-16 Lower-level (7.3 µm) images, with hourly plots of buoy and ship reports [click to play MP4 animation]

Satellite signatures of a phenomenon known as a “sting jet” have been shown previously on this blog here, here and here. GOES-16 (GOES-East) Lower-level (7.3 µm) Water Vapor images (above) revealed another classic example of the “scorpion tail” signature of a sting jet associated with the rapidly-intensifying storm off the coast of North Carolina on 04 January 2018.

The passenger cruise ship Norwegian Breakaway was en route to New York City from the Bahamas when it experienced very strong winds and rough seas early in the morning on 04 January (media story) — it appears as though the ship may have been in the general vicinity of this sting jet feature (ship data), where intense winds were descending to the surface from higher levels of the atmosphere:

A comparison of GOES-16 (GOES-East) and GOES-13 Water Vapor images (below) demonstrated how the GOES-16 improvement in spatial resolution  (2 km at satellite sub-point, vs 4 km for GOES-13) and more frequent imaging (routinely every 5 minutes over the CONUS domain, vs 15-30 minutes for GOES-13) helped to better follow the evolution of the sting jet feature. The 2 known locations of the Norwegian Breakaway around the time period of the image animation are plotted in red.

"Water

Water Vapor images from GOES-16 (6.9 µm, left) and GOES-13 (6.5 µm, right), with the 2 known locations of the Norwegian Breakaway plotted in red [click to play MP4 animation]

The sting jet signature was also apparent on GOES-16 Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below).

GOES-16 Mid-level (6.9 µm) images, with hourly plots of buoy and ship reports [click to play MP4 animation]

GOES-16 Mid-level (6.9 µm) images, with hourly plots of buoy and ship reports [click to play MP4 animation]

GOES-16 Upper-level (6.2 µm) images, with hourly plots of buoy and ship reports [click to play MP4 animation]

GOES-16 Upper-level (6.2 µm) images, with hourly plots of buoy and ship reports [click to play MP4 animation]

In addition, the sting jet signature was evident in a Suomi NPP VIIRS Day/Night Band (0.7 µm) image at 0614 UTC or 1:14 AM Eastern time (below). Through the clouds, the faint glow of city lights in far eastern North Carolina could be seen along the left edge of the image. The cloud features shown using the “visible image at night” VIIRS Day/Night Band were brightly-illuminated by the Moon, which was in the Waning Gibbous phase at 92% of Full. A VIIRS instrument is aboard the JPSS series of satellites, such as the recently-launched NOAA-20.

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

Another view of the sting jet signature was seen in a 250-meter resolution Aqua MODIS Infrared Window (11.0 µm) image at 0725 UTC (below).

Aqua MODIS Infrared Window (11.0 µm) image [click to enlarge]

Aqua MODIS Infrared Window (11.0 µm) image [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]