Sea ice off the coast of Labrador and Newfoundland, Canada

May 3rd, 2016

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]

A comparison of Suomi NPP VIIRS true-color and false-color Red/Green/Blue (RGB) images from the SSEC RealEarth site (above) revealed the intricate structure of sea ice off the coast of Labrador, Canada on 03 May 2016. Snow cover and ice appear as shades of cyan in the false-color image (in contrast to supercooled water droplet clouds, which appear as shades of white).

A larger-scale view using GOES-13 (GOES-East) Visible (0.63 µm) images (below) showed the motion of this sea ice, which extended farther south off the coast of Newfoundland. The general southeastward ice motion was driven by the flow of the Labrador Current.

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

According to data from the Canadian Ice Service, the concentration of this medium to thick “first year ice” (Labrador | Labrador/Newfoundland) was as high as 9/10 to 10/10 (below). The departure of normal of portions of this ice was as high as 9/10 to 10/10 above normal.

Ice concentration off the Labrador coast [click to enlarge]

Ice concentration off the Labrador coast [click to enlarge]

Ice concentration off the coast of Labrador and Newfoundland [click to enlarge]

Ice concentration off the coast of Labrador and Newfoundland [click to enlarge]

Cyclone Fantala in the Indian Ocean

April 16th, 2016

Advanced Dvorak Technique intensity plot for Cyclone Fantala [click to enlarge]

Advanced Dvorak Technique intensity plot for Cyclone Fantala [click to enlarge]

A plot of the Advanced Dvorak Technique (ADT) hurricane intensity estimate (above) revealed that Indian Ocean Cyclone Fantala (19S) exhibited a period of rapid intensification on 15 April 2016, reaching Category 4 intensity with maximum sustained winds of 135 knots at 14 UTC.

EUMETSAT Meteosat-7 Infrared Window (11.5 µm) images (below) showed the formation of a well-defined eye after about 03 UTC.

Meteosat-7 Infrared (11.5 µm) images [click to play animation]

Meteosat-7 Infrared (11.5 µm) images [click to play animation]

A comparison of Meteosat-7 Infrared (11.5 µm) and DMSP-18 SSMI Microwave (85 GHz) images from the CIMSS Tropical Cyclones site (below) showed the eye structure around 15 UTC.

Meteosat-7 Infrared (11.5 µm) and DMSP-18 SSMI Microwave (85 GHz) images [click to enlarge]

Meteosat-7 Infrared (11.5 µm) and DMSP-18 SSMI Microwave (85 GHz) images [click to enlarge]

===== 18 April Update =====

Meteosat-7 Infrared Window (11.5 µm) images [click to play animation]

Meteosat-7 Infrared Window (11.5 µm) images [click to play animation]

During the 17-18 April period Cyclone Fantala reached Category 5 intensity (ADT plot), with maximum sustained winds of 150 knots (making it the strongest tropical cyclone on record in the South Indian Ocean); Fantala also became the longest-lived hurricane-strength tropical cyclone on record for that ocean basin. Meteosat-7 Infrared Window (11.5 µm) images (above) showed the storm reaching peak intensity as it moved just north of the island of Madagascar.

A comparison of Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images (below) offered a detailed nighttime view of the eye of Fantala at 2249 UTC on 17 April. Side lighting from the Moon (in the Waxing Gibbous phase, at 81% of full) helped to cast a distinct shadow within the eye, and also provided a good demonstration of the “visible image at night” capability of the Day/Night Band.

 

Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm images [click to enlarge]

Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm images [click to enlarge]

Middle and upper-atmospheric wave structures in the vicinity of a subtropical jet stream

April 4th, 2016

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, with ECMWF model maximum wind isotachs [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, with ECMWF model maximum wind isotachs [click to enlarge]

A strong (120-knot) subtropical jet stream was moving eastward across the Gulf of Mexico during the 03 April – 04 April 2016 period. During the overnight hours between these 2 days, a Suomi NPP VIIRS Day/Night Band (0.7 µm) image at 0753 UTC (above) revealed a large packet of arc-shaped mesospheric airglow waves south of the axis of the jet stream (as indicated by isotachs of the maximum tropospheric wind speed from the ECMWF model). Note how there were no cloud features which corresponded to these waves in the 0753 UTC VIIRS Infrared Window (11.45 µm) image; since the Moon was in the waning Gibbous phase (at 13% of Full), there was very little lunar illumination of cloud features, so airglow — essentially the “night glow” emitted from a variety of high-altitude (80-105 km) gases (primarily the sodium layer) near the mesopause — was allowing these high-altitude waves to be detected using the sensitive Day/Night Band (reference: “Suomi satellite brings to light a unique frontier of nighttime environmental sensing capabilities”).

During the subsequent daytime hours on 04 April, more interesting (tropospheric) waves were seen in the vicinity of this subtropical jet stream — small packets of waves that were propagating westward, against the ambient flow –one over Florida/Georgia/South Carolina, and another over South Texas. Unfortunately, these features fall into the “What the heck is this?” blog category, so no coherent explanation of them can be offered at this time.

GOES-13 Water Vapor (6.5 µm) images, with ECMWF model maximum wind isotachs [click to play animation]

GOES-13 Water Vapor (6.5 µm) images, with ECMWF model maximum wind isotachs [click to play animation]

An interesting question from Shea Gibson:

Convective snow squalls in the Upper Midwest

April 2nd, 2016

GOES-13 Visible (0.63 µm) images, with hourly surface weather symbols [click to play animation]

GOES-13 Visible (0.63 µm) images, with hourly surface weather symbols [click to play animation]

A vigorous clipper-type shortwave moved rapidly southeastward across the Upper Midwest on 02 April 2016; there were widespread convective elements associated with this system as seen in GOES-13 Visible (0.63 µm) images (above), which produced moderate to heavy snowfall at times (and even thundersnow) creating brief white-out conditions (time-lapse video from the AOSS rooftop camera in Madison, Wisconsin). A sequence of visible images from the polar-orbiting MODIS, VIIRS, and AVHRR instruments (below) provided another detailed view of these convective elements. This disturbance produced strong winds and accumulating snowfall; more information can also be found here from the NWS Chicago.

MODIS, VIIRS, and AVHRR visible images [click to enlarge]

MODIS, VIIRS, and AVHRR visible images [click to enlarge]

A pronounced warm/dry signature of middle-tropospheric subsidence (yellow color enhancement) was evident on GOES-13 Water Vapor (6.5 µm) images (below), which appeared to be along or just ahead of the areas of stronger wind gusts at the surface.

GOES-13 Water Vapor (6.5 µm) images with hourly wind gusts in knots [click to play animation]

GOES-13 Water Vapor (6.5 µm) images with hourly wind gusts in knots [click to play animation]

This area of middle-tropospheric subsidence was located along the leading edge of a strong (110-120 knot) 500 hPa jet, as indicated by the NAM40 model isotachs (below).

GOES-13 Water Vapor (6.5 µm) images with METAR surface reports, surface fronts, and NAM40 500 hPa wind isotachs [click to play animation]

GOES-13 Water Vapor (6.5 µm) images with METAR surface reports, surface fronts, and NAM40 500 hPa wind isotachs [click to play animation]

The convective elements were relatively shallow, with cloud-top infrared brightness temperatures only in the -20 to -30º C range (cyan to darker blue color enhancement) as seen in 4-km resolution GOES-13 Infrared Window (10.7 µm) images (below) and also in 1-km resolution MODIS, VIIRS, and AVHRR infrared images.

GOES-13 Infrared Window (10.7 µm) images, with hourly surface weather symbols [click to play animation]

GOES-13 Infrared Window (10.7 µm) images, with hourly surface weather symbols [click to play animation]

The 24-hour snowfall amounts ending at 12 UTC on 02 and 03 April are shown below, from the NOHRSC site. There was a narrow swath of snowfall in excess of 3 inches just north of the track of the surface low (surface analyses), from northeast Minnesota across Wisconsin to southwest Lower Michigan.

24-hour snowfall amounts (in inches) ending at 12 UTC on 02 and 03 April [click to enlarge]

24-hour snowfall amounts (in inches) ending at 12 UTC on 02 and 03 April [click to enlarge]