Hurricane Force lows in the North Atlantic Ocean

February 15th, 2020 |

GOES-16 Mid-level Water Vapor (6.9 µm) images, with plots of hourly surface wind barbs and gusts (in knots) [click to play animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with plots of hourly surface wind barbs and gusts (in knots) [click to play animation | MP4]

GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed the circulations associated with a pair of Hurricane Force low (surface analyses) during the 13-15 February 2020 period. At the limb of the GOES-16 Full Disk view, plots of hourly surface wind revealed gusts in the 70-80 knots range at stations in Iceland — including Keflavik International Airport near Reykjavik and Akurnes along the southeast coast. One site north of Reykjavik recorded a wind gust of 138 knots.

Sequences of VIIRS Infrared Window (11.45 µm) and True Color RGB images from NOAA-20 and Suomi NPP during those same days as viewed using RealEarth are shown below.

Sequences of VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to play animation]

Sequence of VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to play animation]

Sequence of VIIRS True Color RGB images from NOAA-20 and Suomi NPP [click to play animation]

Sequence of VIIRS True Color RGB images from NOAA-20 and Suomi NPP [click to play animation]

EUMETSAT Meteosat-11 Water Vapor (6.25 µm) images during the 14-16 February period are shown below. Named “Storm Dennis” by the UK Met Office, the system brought high winds to much of Europe.

Meteosat-11 Water Vapor (6.25 µm) images, with hourly wind barbs and gusts (in knots) [click to play animation | MP4]

Meteosat-11 Water Vapor (6.25 µm) images, with hourly wind barbs and gusts (in knots) [click to play animation | MP4]

Additional information about this event is available on the Satellite Liaison Blog.

Global Visible True-Color Imagery

February 14th, 2020 |

True-Color visible imagery from 9 February 2020 (Click to enlarge)

Prediction: This is the most beautiful satellite image you will see today. The above imagery, from the talented Rick Kohrs at the Space Science and Engineering Center, knits (seemingly seamlessly) together vertical local-noon swaths of multispectral visible/near-infrared Geostationary imagery, all using McIDAS-X. At some point in the near future, daily imagery will be created, and then an annual movie. (Click here for an image from 21 March 2019, or from 21 September 2019).

In each image, the sub-point of a satellite used to create the image is evident in the Sun Glint (at 140.2ºE for Himawari-8, or 137.2ºW and 75.2ºW for GOES-17 and GOES-16, respectively). Values at the eastern and western edges do not match up because they are offset by 1 day. A break-point has to be inserted, so why not at the edge?

Mesoscale Convective System in Argentina

February 14th, 2020 |

GOES-16

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (above) showed a large Mesoscale Convective System (MCS) west of Resistencia (station identifier SARE) in far northern Argentina on 14 February 2020 — this MCS developed southeast of an area of low pressure that was situated well north of a slow-moving cold front (surface analyses). The coldest GOES-16 cloud-top infrared brightness temperature was -94.1ºC on the 0750 UTC image.

VIIRS Infrared Window (11.45 µm) images from NOAA-20 (at 0452 UTC) and Suomi NPP (at 0541 UTC) as viewed using RealEarth (below) revealed intricate patterns of cloud-top waves and radial banding.

VIIRS Infrared Window (11.45 µm) images from NOAA-20 (at 0452 UTC) and Suomi NPP (at 0541 UTC) [click to enlarge]

VIIRS Infrared Window (11.45 µm) images from NOAA-20 (at 0452 UTC) and Suomi NPP (at 0541 UTC) [click to enlarge]

Plots of available NOAA-20 NUCAPS sounding points are shown below. NUCAPS profiles immediately north and south of the MCS revealed a very moist and unstable atmosphere, with Total Precipitable Water values around 2.4 inches and Most Unstable air parcel Convective Available Potential Energy (CAPE) values of 4500-5200 J/kg. The red NUCAPS profile dots indicate points where both the infrared and microwave retrievals failed — these are located within the core of the MCS.

Plots of available NUCAPS sounding points at 0341 UTC [click to enlarge]

Plots of available NOAA-20 NUCAPS sounding points [click to enlarge]

NUCAPS profile north of the MCS [click to enlarge]

NOAA-20 NUCAPS profile just north of the MCS [click to enlarge]

NUCAPS profile south of the MCS [click to enlarge]

NOAA-20 NUCAPS profile just south of the MCS [click to enlarge]


Plots of rawinsonde data from Córdoba, Argentina (below) — located not far southwest of the MCS — indicated a tropopause temperature of -74.7ºC at an altitude of 16.4 km on 14 February at 12 UTC.

Plots of rawinsonde data from Córdoba, Argentina [click to enlarge]

Plots of rawinsonde data from Córdoba, Argentina [click to enlarge]

 

Bore-like feature over Lower Michigan

February 13th, 2020 |

GOES-16 Advanced Baseline Imager (ABI) “red” visible imagery (0.64 µm), 1435 – 1840 UTC on 13 February 2020 (Click to enlarge)

TJ Turnage, the Science and Operations Officer (SOO) at the National Weather Service forecast office in Grand Rapids, noted today the presence of smooth, curving bands over Lake Michigan. The animation above shows their development — and the smooth appearance of the bands (just offshore of Ottawa Co, and curving into Allegan Co) is in marked contrast to the north-south oriented lake-effect bands over central Lake Michigan. This falls into the “What the Heck is this?” Blog Category.

An hourly animation that includes surface conditions sheds little light. The bore-like feature seems to arise out of an interaction of the atmospheric flow with Big and Little Sable Points, and surface winds at Muskegon (just north of Ottawa Co) and Holland (in Allegan Co) change as the feature moves over — but no snow is observed at those stations during the bore passage.

GOES-16 Advanced Baseline Imager (ABI) “red” visible imagery (0.64 µm) and surface METARS hourly from 1300 – 2100 UTC on 13 February 2020 (Click to enlarge)

Radar imagery (from the College of Dupage) also shows little return associated with the bore-like features.  (Click to see images from 1720 and 1800 UTC, when the bands were on shore).

NEXRAD Composite Radar Imagery (Composite Reflectivity) centered on MI, 1655-1820 UTC on 13 february 2020 (Click to enlarge)

 

Water vapor imagery, below, suggests that the stable layer that is trapping the energy and causing the bore-like feature originated near Big and Little Sable Points, around 1600 UTC.  The enhancement also suggests the bore-like feature is higher than the tops of lake-effect bands in the middle of Lake Michigan.  (Click here for a rocking animation of the water vapor imagery;  the rocking allows for better tracking of the impulse back to the source near the Sables, its earliest hint is at 1610 UTC — vs. about 1635 UTC in visible imagery).

GOES-16 ABI Band 10 (7.34 µm, low-level water vapor) infrared imagery, 1520 to 2015 UTC, 13 February 2020 (Click to play animated gif)

GOES-16 ABI Band 2 (0.64 µm) visible imagery, 1520 to 2015 UTC, 13 February 2020 (Click to play animated gif)

Bore-like features require stable layers.  The Gaylord Michigan sounding at 1200 UTC — upstream from the region out of which the bore emerged — shows several inversion layers.  The weighting function for the sounding (from this site) shows peak contributions for 7.34 µm (indeed, from all water vapor channels) from above 500 mb.  The coldest brightness temperature in the bands is -28 º C;  based on the Gaylord sounding, that’s a pressure level near 560 mb.  These Bore-like features are not Lake-Effect snow bands, despite having the correct aspect ratio — their width and length both suggest Lake-effect bands, but their height suggests otherwise.

NOAA-20 overflew this region shortly after 1700 UTC, and a NUCAPS sounding is close to the Michigan shoreline, just east of Holland, where the cloud band is coming onshore. The sounding from NUCAPS at that point/time is below.  The very smooth sounding does bear a passing resemblance to the Gaylord Sounding, but the smoothness of the NUCAPS profile — sampling a volume of air that in this case is about as wide as a county, makes identification of sharp inversions difficult.

NOAA-20 NUCAPS Profile points over Lake Michigan and lower Michigan, ca. 1730 UTC on 13 February 2020 (Click to enlarge)

NUCAPS Profile of temperature and moisture, 17 UTC on 13 February 2020 (Click to enlarge)