Interesting wave features near Guadalupe Island

February 24th, 2014
GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

Hat-tip to Matt Sitkowski and Carl Parker of The Weather Channel for the heads-up on some interesting wave features that could be seen in the vicinity of Guadalupe Island on McIDAS images of GOES-15 0.63 µm visible channel data (above; click image to play animation) on 24 February 2014. Apparently a gravity wave had propagated northwestward through the region during the morning hours, perturbing the depth of the marine boundary layer (MBL) such that undulations in the MBL stratocumulus clouds were quite evident. In addition, an unusual “dry pulse” propagated outward from Guadalupe Island (located in the center of the images). These wave features eventually became hidden as layers of middle and high clouds overspread the area from the southwest.

AWIPS images of GOES-15 0.63 µm visible channel data with overlays of Real-Time Mesoscale Analysis (RTMA) surface winds (below) showed that the surface flow was very light or even calm across much of the Guadalupe Island region during the time that the “dry pulse” was most evident on visible imagery.

GOES-15 0.63 µm visible images with RTMA surface winds

GOES-15 0.63 µm visible images with RTMA surface winds

Low-level “barrier jet” along the southeast coast of Greenland

December 29th, 2013
GOES-13 6.5 µm water vapor images with Metop ASCAT scatterometer winds and surface METARs and surface analyses (click to play animation)

GOES-13 6.5 µm water vapor images with Metop ASCAT scatterometer winds and surface METARs and surface analyses (click to play animation)

AWIPS images of GOES-13 6.5 µm water vapor channel data with available overpasses of Metop ASCAT surface scatterometer winds (above; click image to play animation) revealed the presence of a low-level “barrier jet” along the southeast coast of Greenland on 29 December 2013. Maximum ASCAT wind speeds were 58 knots at 12:16 UTC, 62 knots at 13:57 UTC, and 62 knots at 22:09 UTC. It is interesting to note that a secondary area of low pressure was seen rotating around the primary low, and appeared to be rapidly intensifying judging from the quick development of a “corkscrew” appearance on the water vapor imagery near the end of the animation. ASCAT winds along the northwestern periphery of this secondary low were as high as 53 knots at 22:09 UTC.

The cyclonic circulation around the quasi-stationary area of low pressure located east of Greenland encountered the abrupt rise in topography of the island (below), which caused an acceleration of the flow known as a “barrier jet”.

Topography of Greenland, with Metop ASCAT scatterometer winds and surface METAR reports and surface analysis

Topography of Greenland, with Metop ASCAT scatterometer winds and surface METAR reports and surface analysis

Strong storm in the North Atlantic Ocean

December 12th, 2013
GOES-13 6.5 µm water vapor channel images, with surface analysis and METAR surface reports

GOES-13 6.5 µm water vapor channel images, with surface analysis and METAR surface reports

A large and strong cyclone was intensifying in the North Atlantic Ocean just south of Greenland on 12 December 2013. GOES-13 6.5 µm water vapor channel images with 06 UTC, 12 UTC, 18 UTC, and 00 UTC surface analyses and surface reports (above) showed that the central pressure of the storm deepened to 942 hPa at 18 UTC — and the strong pressure gradient between the low and a 1032 hPa high situated over northern Greenland was forecast to produce a broad region of hurricane-force winds.

EUMETSAT Metop ASCAT scatterometer surface winds at 22:41 UTC (below) highlighted 3 areas over the water which contained a number of remotely-sensed winds of 50 knots or higher (red barbs). The strongest wind velocity within this ASCAT swath was 54 knots, located in the largest area of red wind barbs south of the storm center.

GOES-13 6.5 µm water vapor image and ASCAT scatterometer surface winds

GOES-13 6.5 µm water vapor image and ASCAT scatterometer surface winds

Near the time of the 22:41 UTC ASCAT data, surface winds were a steady 50 knots from the north-northwest at Cape Dyer, Nunavut, Canada (station idendifier CWFD) — and the peak wind gust at that station was 56 knots several hours prior at 18 UTC. In southern Greenland, the peak wind gust at Narsarsuaq (station identifier BGBW) was 71 knots, occcurring earlier in the day at 13 UTC (below).

Time series of meteorological data at Cape Dyer, Nunavut, Canada

Time series of meteorological data at Cape Dyer, Nunavut, Canada

Time series of meteorological data at Narsarsuaq, Greenland

Time series of meteorological data at Narsarsuaq, Greenland

GOES-13 6.5 µm water vapor images at 30-minute intervals (below; click image to play animation) displayed an interesting range of signatures as moisture wrapped around the very large storm.

GOES-13 6.5 µm water vapor channel images (click to play animation)

GOES-13 6.5 µm water vapor channel images (click to play animation)

Formation of an “Otter Eddy” in Monterey Bay, California

May 13th, 2013
GOES-13 0.63 µm visible channel images (click image to play animation)

GOES-13 0.63 µm visible channel images (click image to play animation)

Strong northwesterly winds along the California coast interacted with the complex terrain and orientation of Monterey Bay to promote the formation of a cyclonic coastal eddy (known locally as an “Otter Eddy”) early in the day on 13 May 2013. McIDAS images of GOES-15 0.63 µm visible channel data (above; click image to play animation) showed the evolution of the eddy feature, which gradually dissipated by the early afternoon hours. “MRY” denotes the location of Monterey.

Farther to the north, an interesting type of “bow shock wave” formed downwind of Point Reyes (labelled “PR” on the images). Better detail of this feature could be seen in an AWIPS image of Suomi NPP VIIRS 0.64 µm visible channel data (below). At the time of this image, surface winds at the offshore buoy just to the north of Point Reyes were gusting to 33 knots (38 mph).

Suomi NPP VIIRS 0.64 µm visible channel image

Suomi NPP VIIRS 0.64 µm visible channel image