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Lee-side cold frontal gravity wave

By Scott Bachmeier •

As a cold front moved rapidly southward across the Great Plains (surface analyses) on 05 February 2018, the signature of a deep-tropospheric lee-side cold frontal gravity wave (reference) could be seen on GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above; also available as an MP4 animation). In addition, the initial... Read More

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, middle) and Upper-level (6.2 µm, right) Water Vapor images, with hourly surface wind barbs plotted in cyan [click to play animation]

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, middle) and Upper-level (6.2 µm, right) Water Vapor images, with hourly surface wind barbs plotted in cyan [click to play animation]

As a cold front moved rapidly southward across the Great Plains (surface analyses) on 05 February 2018, the signature of a deep-tropospheric lee-side cold frontal gravity wave (reference) could be seen on GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above; also available as an MP4 animation). In addition, the initial gravity wave was soon followed by a secondary lee-side gravity wave, which could be seen moving southward over the northern Texas Panhandle by the end of the animation.

Plots of the weighting function (or “contribution function”) for each of the three GOES-16 Water Vapor bands (below) are calculated using 05 February/12 UTC rawinsonde data from Dodge City, Kansas — which was south of the cold front at that time. The peak pressure level for all three weighting function plots was in the 442-497 hPa range, giving some indication of the depth of these vertically-propagating gravity waves.

Weighting function plots for each of the three GOES-16 Water Vapor bands, calculated using 05 February/12 UTC rawinsonde data from Dodge City, Kansas [click to enlarge]

Weighting function plots for each of the three GOES-16 Water Vapor bands, calculated using 05 February/12 UTC rawinsonde data from Dodge City, Kansas [click to enlarge]

GOES-16 Water Vapor weighting functions using 06 February/00 UTC rawinsonde data from Amarillo, Texas — where the surface cold front had passed about 3 hours earlier — are shown below. Note that in the drier post-frontal air mass, the peak pressures for the 3 water vapor bands had increased, descending to the 477 to 684 hPa pressure levels. This comparison helps to underscore the dependence of water vapor weighting function height on the temperature and/or moisture profile of the atmosphere.

Weighting function plots for each of the three GOES-16 Water Vapor bands, calculated using 06 February/00 UTC rawinsonde data from Amarillo, Texas [click to enlarge]

Weighting function plots for each of the three GOES-16 Water Vapor bands, calculated using 06 February/00 UTC rawinsonde data from Amarillo, Texas [click to enlarge]

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Ice in the western Great Lakes

By Scott Bachmeier •

After several days of cold temperatures, ice coverage in the western half of Lake Superior began to increase — and GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the motion of some of this lake ice (which was driven by a combination of surface winds and lake circulations) on 04 February 2018.... Read More

GOES-16 "Red" Visible (0.64 µm) images, with plots of hourly surface reports [click to play animation]

GOES-16 “Red” Visible (0.64 µm) images, with plots of hourly surface reports [click to play animation]

After several days of cold temperatures, ice coverage in the western half of Lake Superior began to increase — and GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the motion of some of this lake ice (which was driven by a combination of surface winds and lake circulations) on 04 February 2018. That morning a number of locations in northern and northeastern Minnesota reported low temperatures in the -20 to -40 ºF range, with -43 ºF at Embarrass (the coldest location in the Lower 48 states).

With an overpass of the Landsat-8 satellite at 1646 UTC, a 30-meter resolution False-color Red-Green-Blue (RGB) image (below) provided a very detailed view of a portion of the Lake Superior ice. NOAA-GLERL analyzed the mean ice concentration of Lake Superior to be at 23.9% ; the Canadian Ice Service analyzed much of the new lake ice to have a concentration of 9/10ths to 10/10ths.

Landsat-8 False-color RGB image [click to enlarge]

Landsat-8 False-color RGB image [click to enlarge]

Magnified sections of the Landsat-8 RGB image swath are shown below, moving from northeast to southwest.

Landsat-8 False-color RGB image [click to enlarge]

Landsat-8 False-color RGB image [click to enlarge]

Landsat-8 False-color RGB image [click to enlarge]

Landsat-8 False-color RGB image [click to enlarge]

Landsat-8 False-color RGB image [click to enlarge]

Landsat-8 False-color RGB image [click to enlarge]

Landsat-8 False-color RGB image [click to enlarge]

Landsat-8 False-color RGB image [click to enlarge]

Moving to the south, a closer look at Green Bay in northeastern Wisconsin revealed a few small ice floes drifting from the north end of the bay into Lake Michigan (below).

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with plots of hourly surface reports [click to play animation]

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Eruption of Volcán de Fuego in Guatemala

By Scott Bachmeier •

After a series of occasional weak emissions during the previous month, a small eruption of Volcán de Fuego began during the pre-dawn hours on 01 February 2018. The thermal anomaly or “hot spot” could be seen on GOES-16 (GOES-East) Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images... Read More

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Snow/Ice” (1.61 µm, top), Near-Infrared “Cloud Particle Size” (2.24 µm, middle) and Shortwave Infrared (3.9 µm, bottom) images [click to animate]

After a series of occasional weak emissions during the previous month, a small eruption of Volcán de Fuego began during the pre-dawn hours on 01 February 2018. The thermal anomaly or “hot spot” could be seen on GOES-16 (GOES-East) Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images (above). In terms of the two Near-Infrared bands, even though the 1.61 µm band has better spatial resolution (1 km at satellite sub-point), the 2-km resolution 2.24 µm band is spectrally located closer to the peak emitted radiance of very hot features such as active volcanoes or large fires (spectral response function plots).

Multi-spectral retrievals of Ash Cloud Height from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) indicated that volcanic ash extended to altitudes in the 4-6 km range (yellow to green enhancement), with isolated 7 km pixels at 1315 UTC. The product also showed the effect of a burst of southwesterly winds just after 11 UTC, which began to transport some of the ash northeastward (as mentioned in the 1332 UTC advisory).

GOES-16 Ash Height product [click to animate]

GOES-16 Ash Height product [click to animate]

At 1624 UTC, a 30-meter resolution Landsat-8 False-color Red-Green-Blue (RGB) image viewed using RealEarth (below) showed the primary ash plume drifting to the west, with some lower-altitude ash spreading out northward and southward. A thermal anomaly was also evident at the summit of the volcano.

Landsat-8 False-color RGB image [click to enlarge]

Landsat-8 False-color RGB image [click to enlarge]

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Storm-force low in the central Atlantic Ocean

By Scott Bachmeier •

The compact circulation of an occluded surface low over the central Atlantic Ocean could be seen on GOES-16 (GOES-East) “Red” Visible (0.64 µm) images on 29 January 2018 (above); surface analyses indicated that the system was producing Storm Force (48-55 knot) winds.This surface low was located beneath a larger upper-level low, as... Read More

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

The compact circulation of an occluded surface low over the central Atlantic Ocean could be seen on GOES-16 (GOES-East) “Red” Visible (0.64 µm) images on 29 January 2018 (above); surface analyses indicated that the system was producing Storm Force (48-55 knot) winds.

This surface low was located beneath a larger upper-level low, as seen on GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below). Very dry air (yellow to red enhancement) was evident just to the south and southwest of the storm.

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm) images [click to play MP4 animation]

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) images [click to play MP4 animation]

Hourly images of a (preliminary, non-operational) GOES-16 Deep-Layer Wind Shear product (calculated using Low-level and Mid-upper level GOES-16 Derived Motion Winds) are shown below — they revealed that the surface low was protected within the favorable low-shear environment of the upper low circulation, with more unfavorable high values of shear immediately surrounding it.

GOES-16 Deep-layer Wind Shear products [click to play animation]

GOES-16 Deep-layer Wind Shear products [click to play animation]

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