Water vapor imagery: upper level vortices and jet streaks

September 13th, 2006 |

GOES-12 water vapor animation

A QuickTime animation of GOES-12 imager 6.5 micrometer (“water vapor channel”) imagery (above) reveals an interesting vortex associated with a cutoff upper-level low which was migrating eastward from Illinois to Ohio on 13 Sepember. Several pulses of convection can be seen developing along the periphery of the vortex. In addition, GOES-12 sounder total column ozone values were slightly elevated within the core of the vortex (~350 Dobson Units, compared to the background of ~300 DU), suggesting that some stratospheric air was also present.

Also of interest were the subtle indications that the structure of the jet stream (within the southeastern quadrant of the upper low circulation) was very complex — note the “streaky” appearance on the water vapor images across the Tennessee and Ohio River Valley regions, especially evident on the 1km resolution MODIS water vapor channel (below, upper right panel), but also apparent on the 10km resolution GOES-12 sounder water vapor channel (below, lower left panel). The relatively smooth NAM 300mb wind speeds simply indicated a broad jet streak core oriented SW-NE from Mississippi to Virginia, with a 500mb jet streak axis located farther to the northwest. The striated appearance of the water vapor imagery suggests that the broad jet core region may have been comprised of multiple jet streaks (likely existing at different altitudes).

The lower right panel below is the CRAS model forecast of the GOES water vapor channel, close to the time of the actual satellite images in the other 3 panels; while the CRAS model was unable to resolve the fine mesoscale structure associated with the multiple jet streak cores, it did offer a good prognosis of the “3-pronged structure” of the leading edge of the dry slot.
AWIPS water vapor channel comparison

Ex-hurricane Ophelia over Ireland and the United Kingdom

October 16th, 2017 |

Meteosat-10 Water Vapor (6.25 µm) images, with hourly surface wind gusts (knots) plotted in red [click to play MP4 animation]

Meteosat-10 Water Vapor (6.25 µm) images, with hourly surface wind gusts (knots) plotted in red [click to play MP4 animation]

After reaching Category 3 intensity over the eastern Atlantic Ocean on 14 October, Hurricane Ophelia (storm track) rapidly underwent transition to an extratropical storm which eventually spread high winds across much of Ireland and the United Kingdom on 16 October 2017. EUMETSAT Meteosat-10 upper-level Water Vapor (6.25 µm) (above) and lower-level Water Vapor (7.35 µm) images (below) revealed the familiar “scorpion tail” signature of a sting jet (reference). Hourly wind gusts (in knots) from primary reporting stations are plotted in red.

Meteosat-10 Water Vapor (7.35 µm) images, with hourly surface wind gusts (knots) plotted in red [click to play MP4 animation]

Meteosat-10 Water Vapor (7.35 µm) images, with hourly surface wind gusts (knots) plotted in red [click to play MP4 animation]

Two sites with notable wind gusts were Cork, Ireland (67 knots at 0930 UTC) and Valley, UK (70 knots at 1500 UT), shown below. In fact, a wind gust of 103 knots (119 mph or 191 km/hour) was reported at the Fastnet Rock Lighthouse off the southwest coast of Ireland.

Time series plot of surface data from Cork, Ireland [click to enlarge]

Time series plot of surface data from Cork, Ireland [click to enlarge]

Time series plot of surface data from Valley, United Kingdom [click to enlarge]

Time series plot of surface data from Valley, United Kingdom [click to enlarge]

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

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

In a toggle between Terra MODIS (overpass time around 1159 UTC) and Aqua MODIS (overpass time around 1345 UTC) true-color Red-Green-Blue (RGB) imagery (above), a somewhat hazy appearance was seen over the Irish Sea on the Terra MODIS image. This was due to an airborne plume of sand from the Sahara Desert (UK Met Office story).

In fact, blowing sand was observed about 3 hours later at Isle of Man, from 1520-1620 UTC — during that time period their surface winds gusted to 68 knots (78 mph), and surface visibility was reduced to 2.2 miles (below).

Time series plot of surface data from Isle of Man [click to enlarge]

Time series plot of surface data from Isle of Man [click to enlarge]

Storm “Doris” affects the British Isles

February 23rd, 2017 |

Meteosat-10 Water Vapor (6.25 µm) images, with hourly surface wind gusts in knots [click to play animation]

Meteosat-10 Water Vapor (6.25 µm) images, with hourly surface wind gusts in knots [click to play animation]

Storm “Doris” affected the British Isles on 23 February 2017, producing strong winds and heavy rainfall. The mid-latitude cyclone rapidly intensified from a central pressure of 1004 hPa at 12 UTC on 22 February to 972 hPa at 12 UTC on 23 February (surface analyses) . EUMETSAT Meteosat-10 Water Vapor (6.25 µm) images (above) exhibited the “scorpion tail” signature of a sting jet (Monthly Weather Review | Wikipedia), and surface wind gusts included 58 knots at Dublin, 64 knots at Wittering and 69 knots at Valley.

The corresponding daylight Meteosat-10 High Resolution Visible (0.8 µm) images (below) revealed better detail of the various cloud structures associated with the storm.

Meteosat-10 High Resolution Visible (0.8 µm) images, with hourly surface wind gusts in knots [click to play animation]

Meteosat-10 High Resolution Visible (0.8 µm) images, with hourly surface wind gusts in knots [click to play animation]

True-color Red/Green/Blue (RGB) images from Terra/Aqua MODIS and Suomi NPP VIIRS visualized using RealEarth are shown below. EUMETSAT posted a natural-color RGB animation here.

Terra MODIS (1039 UTC), Aqua MODIS (1226 UTC) and Suomi NPP VIIRS (1248 UTC) true-color RGB images [click to enlarge]

Terra MODIS (1039 UTC), Aqua MODIS (1226 UTC) and Suomi NPP VIIRS (1248 UTC) true-color RGB images [click to enlarge]

Christmas Blizzard

December 26th, 2016 |

GOES-13 Water Vapor (6.5 µm) images, with hourly surface weather symbols [click to play animation]

GOES-13 Water Vapor (6.5 µm) images, with hourly surface weather symbols [click to play animation]

A mid-latitude cyclone intensified as it moved northeastward across Nebraska, the eastern Dakotas and northern Minnesota (3-hourly surface analyses) during 25 December26 December 2016. GOES-13 (GOES-East) Water Vapor (6.5 µm) images (above) showed distinct banding within the warm conveyor belt, a well-defined dry slot, and a large comma head that formed from the cold conveyor belt. The storm produced blizzard conditions across much of the Northern Plains and Upper Midwest, with heavy snowfall (as much as 22.0 inches in western North Dakota), freezing rain (ice accretion as thick as 0.5 inch in Minnesota and North Dakota) , sleet (up to 2.0 inches deep in Minnesota) and heavy rainfall; in Kansas there were also a few tornadoes (SPC storm reports).

A noteworthy characteristic of the storm was very strong winds — a closer view of GOES-13 Water Vapor imagery with hourly plots of surface wind gusts (in knots) is shown below.

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

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

Note the swath of wind gusts in the 50-60 knot range which progressed across central and northeastern Nebraska into northwestern Iowa and finally southwestern Minnesota during the 02 UTC to 12 UTC period on 26 December — this was pointed out in a tweet by Anthony Sagliani as a “sting jet” feature:


As observed in previous sting jet cases (03 Jan 2012 | 28 Oct 2013), the strongest winds occurred near the curved “scorpion tail” signature seen in the water vapor imagery (which marked the leading edge of the cold conveyor belt as it advanced into the rear edge of the dry slot of the cyclone circulation).

A comparison of Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm) and Water Vapor (6.7 µm) images at 2001 UTC on 25 December is shown below.

Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm) and Water Vapor (6.7 µm) images [click to enlarge]

Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm) and Water Vapor (6.7 µm) images [click to enlarge]

A closer view with Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images at 1952 UTC on 25 December (below) showed a detailed view of the banded cloud structures from Kansas into South Dakota, as well as small overshooting tops associated with thunderstorms in southeastern South Dakota and southwestern Minnesota. This storm produced the first Christmas Day thunderstorms on record in both Sioux Falls and Rapid City, South Dakota; thundersnow was also observed in Bismarck, North Dakota.

Suom NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suom NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]