Storm Frank over the Northeast Atlantic Ocean

December 30th, 2015

Northeast Atlantic surface analysis maps [click to enlarge]

Northeast Atlantic surface analysis maps [click to enlarge]

Surface analysis maps over the Northeast Atlantic Ocean (above) showed the rapid intensification of an area low pressure — named Storm Frank by the UK Met Office and Met Éireann — during the 29-30 December 2015 time period. As the storm moved northward toward Iceland, the central pressure of Frank explosively deepened from 966 hPa at 06 UTC on 29 December to 928 hPa at 06 UTC on 30 December, with the tight pressure gradient producing hurricane-force winds over a large area.

EUMETSAT Meteosat-10 Visible (0.75 µm, 1-km resolution) images (below; also available as a 10-Mbyte animated GIF) depicted the well-defined center of circulation of Storm Frank during the daylight hours on 29 December, as it was intensifying south of Iceland and west of Ireland.

Meteosat-10 Visible (0.75 µm) images [click to play MP4 animation]

Meteosat-10 Visible (0.75 µm) images [click to play MP4 animation]

Meteosat-10 Infrared (10.8 µm, 3-km resolution) and Water Vapor (6.25 µm, 3-km resolution) images (below; also available as animated GIFs: 33 Mbtye Infrared and 21 Mbyte Water Vapor) showed Storm Frank as the center eventually moved over Iceland early in the day on 30 December.

Meteosat-10 Infrared (10.8 µm) images [click to play MP4 animation]

Meteosat-10 Infrared (10.8 µm) images [click to play MP4 animation]

Meteosat-10 Water Vapor (6.25 µm) images [click to play MP4 animation]

Meteosat-10 Water Vapor (6.25 µm) images [click to play MP4 animation]

As the 928 hPa low pressure moved over Iceland (below), time series plots of data from various surface stations revealed winds gusting to over 50 knots at Egilsstaðir BIEG and Akureyri BIAR; farther to the east over the British Isles, wind gusts exceeded 50 knots at Cork EICK and Stornoway EGPL, with gusts over 60 knots at Sørvágur/Vágar EKVG and Benbecula EGPL. In the North Sea off the coast of Norway, strong winds and high waves were responsible for a barge breaking free of its moorings and drifting near oil fields (media report); there was also one fatality and 2 injuries on an oil rig (media report).

Meteosat-10 Water Vapor (6.25 µm) image at 0630 UTC on 30 December, with surface station IDs [click to enlarge]

Meteosat-10 Water Vapor (6.25 µm) image at 0630 UTC on 30 December, with surface station IDs [click to enlarge]

The NWS Ocean Prediction Center created longer satellite image animations covering the entire life cycle of the storm (below).

 

Rope Cloud over the Gulf of Mexico

December 28th, 2015

GOES-13 Visible Imagery (0.63 µm) and surface reports [click to enlarge]

GOES-13 Visible Imagery (0.63 µm) and surface reports [click to enlarge]

Visible Imagery over the Gulf of Mexico on 28 December 2015 revealed the presence of a Rope Cloud. Rope Clouds are handy features in satellite imagery because they reveal the location of the surface cold front, and the animation above shows wind shifts from southerly to westerly as the Rope Cloud moves past. (A good Rope Cloud example also occurred in November).

Visible imagery from just after sunrise, below, show long shadows cast by individual towers along the Rope Cloud. The shadows shorten quickly as the sun rises in the sky. Infrared imagery (Link) shows the towers as well, indicated with cooler brightness temperatures.

GOES-13 Visible Imagery (0.63 µm), 1300-1430 UTC on 28 December 2015 [click to enlarge]

GOES-13 Visible Imagery (0.63 µm), 1300-1430 UTC on 28 December 2015 [click to enlarge]

A larger-scale view using 1-km resolution Terra MODIS Visible (0.65 µm) and Infrared (11.0 µm) images at 1702 UTC, below, showed that the rope cloud stretched for nearly 1000 miles along the leading edge of the cold front (surface analyses). One small area of convection had begun to develop along the cold front at that time, which exhibited a cloud-top IR brightness temperature of -31º C (dark blue color enhancement).

MODIS Visible (0.65 µm) and Infrared (11.0 µm) images [click to enlarge]

MODIS Visible (0.65 µm) and Infrared (11.0 µm) images [click to enlarge]

Surges of cold air into the southern Gulf of Mexico will frequently spill through a gap in topography (the Chivela Pass between the Sierra Madre de Oaxaca and the Sierra Madre de Chiapas) in southern Mexico, emerging as a region of strong winds in the Gulf of Tehuantapec. ASCAT Scatterometer winds from METOP-A, below, show a concentrated region of 30-knot winds just off the coast of southern Mexico.

ASCAT Scatterometer Winds, 0248 UTC on 29 December, 2015 [click to enlarge]

ASCAT Scatterometer Winds, 0248 UTC on 29 December, 2015 [click to enlarge]

Christmas Full Moon Day/Night Band images

December 25th, 2015

Suomi NPP VIIRS Day/Night Band image swaths [click to enlarge]

Suomi NPP VIIRS Day/Night Band image swaths [click to enlarge]

A rare Full Moon on Christmas — the last occurrence was in 1977, and the next will be in 2034 — was reached at 1111 UTC, and provided some compelling “visible images at night” from the Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB). The animation above shows the coverage of 4 consecutive DNB image swaths across much of North America, as viewed using RealEarth.

Taking a closer look at various regions and features, we will begin with the Northeast US at 0610 UTC (below). One item of interest was the narrow fingers of valley fog that were forming in parts of Pennsylvania and New York, where strong radiational cooling under cloud-free skies was allowing the surface air temperatures to cool into the 30s and 40s F.

Suomi NPP VIIRS 0.7 µm Day/Night Band image centered over the Northeast US [click to enlarge]

Suomi NPP VIIRS 0.7 µm Day/Night Band image centered over the Northeast US [click to enlarge]

Over the Southeast US at 0749 UTC (below), ample illumination by the Full Moon provided a very detailed nighttime view of the tops of numerous thunderstorms that had developed along and ahead of a cold frontal boundary (surface analysis). Note the appearance of several bright white areas at the tops of some thunderstorms, a signature of cloud illumination by intense lightning activity. In addition, temperatures ahead of the cold front were unusually warm for 25 December — for example, new records for the warmest low temperature for the date were set at both Mobile, Alabama and Pensacola, Florida (with 75º F and 71º F, respectively).

Suomi NPP VIIRS Day/Night Band image centered over the Southeast US [click to enlarge]

Suomi NPP VIIRS Day/Night Band image centered over the Southeast US [click to enlarge]

Farther to the north, a DNB image centered over South Dakota (below) showed a great deal of variability in snow cover across that area; the effect of deeper snow cover on surface air temperatures could also be seen in the surface observations at that time, with the colder readings generally coinciding with sites having snow on the ground.

Suomi NPP VIIRS Day/Night Band image centered over South Dakota [click to enlarge]

Suomi NPP VIIRS Day/Night Band image centered over South Dakota [click to enlarge]

Even farther to the north, it could be seen that ice covered a significant portion of Hudson Bay, Canada (below). In southern parts of Hudson Bay where open water still existed, numerous “lake effect” cloud bands could be seen due the northwesterly flow of very cold arctic air across the water.

Suomi NPP VIIRS Day/Night Band image centered over Hudson Bay, Canada [click to enlarge]

Suomi NPP VIIRS Day/Night Band image centered over Hudson Bay, Canada [click to enlarge]

A DNB image centered over the Western US at 0930 UTC (below) revealed features such as snow pack over the higher terrain of the Sierra Nevada in California (where temperatures at the time ranged from 55º F in the desert at Needles KEED to 1º F in the mountains at South Lake Tahoe KTVL), and a variety of open-cell and closed-cell convection over the adjacent offshore waters of the Pacific Ocean.

Suomi NPP VIIRS Day/Night Band image centered over the western US [click to enlarge]

Suomi NPP VIIRS Day/Night Band image centered over the western US [click to enlarge]

Finally, a DNB image centered over Alaska and the Yukon Territory of Canada at 1111 UTC (below) showed widespread snow cover over the cloud-free interior regions, with the thick cloud shield from a Gulf of Alaska storm moving over southwestern and southcentral Alaska. Very cold surface air temperatures at or below -30º F could be seen at a number of sites in the interior areas, with -42º F being reported at the time in Arctic Village, Alaska PARC (their minimum temperature later dropped to -45º F).

Suomi NPP VIIRS Day/Night Band image centered over Alaska and the Yukon Territory [click to enlarge]

Suomi NPP VIIRS Day/Night Band image centered over Alaska and the Yukon Territory [click to enlarge]

Widespread severe weather outbreak

December 24th, 2015

SPC preliminary storm reports [click map for complete listing]

SPC preliminary storm reports [click map for complete listing]

As shown above, a widespread outbreak of severe weather occurred on 23 December – 24 December 2015 (surface analysis maps), centered on the Mississippi Valley and Ohio Valley regions of the US. There were at least 14 fatalities in Mississippi, Tennessee, and Arkansas — and storm damage surveys (NWS Memphis PNS) showed that there were two long-track tornadoes in the Mid-South region: one EF3-rated that was on the ground for 63 miles in northwestern Mississippi, and another EF4-rated that was on the ground for 75 miles from northern Mississippi to far southwestern Tennessee (below).

Preliminary tornado damage paths [click to enlarge]

Preliminary tornado damage paths [click to enlarge]

Daytime GOES-13 (GOES-East) Visible (0.63 µm, 1-km resolution) images on 23 December (below) showed the development of several lines of severe thunderstorms — some with bowing segments earlier in the day — with many storms exhibiting signatures of well-defined Overshooting Tops and having strong Cloud-Top Cooling rates.

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

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

Longer animations of GOES-13 Infrared (10.7 µm, 4-km resolution) and Water Vapor (6.5 µm, 4-km resolution) images that extended into the nighttime hours of the severe weather outbreak are shown below.

GOES-13 Infrared (10.7 µm) images [click to play animation]

GOES-13 Infrared (10.7 µm) images [click to play animation]

GOES-13 Water Vapor (6.5 µm) images [click to play animation]

GOES-13 Water Vapor (6.5 µm) images [click to play animation]