Orographic standing wave cloud over the Mid-Atlantic states

December 17th, 2018 |

Topography + GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images, with pilot reports of turbulence [click to play MP4 animation]

Topography + GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images, with pilot reports of turbulence [click to play MP4 animation]

GOES-16 (GOES-East) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) showed the development of an orographic standing wave cloud — downwind of the Appalachian Mountains (topography) — over the Mid-Atlantic states on 17 December 2018. North of the wave cloud, widespread short-wavelength mountain waves were seen at lower elevations over and to the lee of the high terrain (even extending out over the Atlantic Ocean off the coast of New Jersey and New York). There were scattered pilot reports of turbulence across the region, with Severe turbulence being reported around 18 UTC and 00 UTC.

A comparison of GOES-16 Mid-level Water Vapor, Cloud Top Phase and Cloud Top Height products at 2007 UTC (below) indicated that this wave cloud was composed of Cirrus with maximum cloud tops around 30,000 feet.

GOES-16 Mid-level Water Vapor (6.9 µm), Cloud Top Phase and Cloud Top Height products [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm), Cloud Top Phase and Cloud Top Height products [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) image at 2102 UTC, showing the orientation of a nortwest-southeast cross section [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) image at 2102 UTC, showing the orientation of a northwest-southeast cross section [click to enlarge]

A GOES-16 Water Vapor image at 2102 UTC (above) showed the orientation of a northwest-to-southeast cross section of RUC40 model Relative Humidity, Wind Speed and Adiabatic Omega fields (below). In the middle of the cross section, a couplet of downward/upward motion aloft was seen over the Glen Allen VA area, with higher relative humidity values (shades of blue) above the 500 hPa pressure level corresponding to the wave cloud.

Northwest-southeast cross section of RUC40 model Relative Humidity, Wind Speed and Adiabatic Omega [click to enlarge]

Northwest-southeast cross section of RUC40 model Relative Humidity, Wind Speed and Adiabatic Omega [click to enlarge]

The standing wave cloud developed in the exit region of a branch of the polar jet stream that was diving southeastward across the Great Lakes — strong deceleration created an axis of deformation oriented from southwest to northeast (below), helping the stretch the wave cloud  feature as it slowly pivoted toward the southeast and along the coast. The strong downward motion component of the Omega couplet seen in the cross section was responsible for the relatively sharp upwind (northwest) edge exhibited by the wave cloud.

GOES-16 Mid-level Water Vapor (6.9 µm) images, with RAP40 model 250 hPa isotachs and deformation vectors [click to play animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with RAP40 model 250 hPa isotachs and deformation vectors [click to play animation | MP4]

A toggle between NOAA-20 VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images viewed using RealEarth (below) provided a detailed view of the wave cloud at 1825 UTC. The coldest cloud-top infrared brightness temperatures were around -50ºC (bright yellow enhancement), which was just above the 300 hPa pressure level on 00 UTC soundings at Roanoke/Blacksburg and Wallops Island Virginia.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

As pointed out by Jonathan Blaes (NWS Raleigh), these standing wave clouds can have an effect on surface temperatures beneath the feature:



A comparison of 1812 UTC Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm), Near-Infrared “Cirrus” (1.37 µm) and Water Vapor (6.7 µm) images with plots of maximum temperatures on 17 December (below) revealed that high temperatures were confined to the upper 50s F beneath the wave cloud, in contrast to low 60s F on either side where incoming solar radiation was not diminished.

Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm), Near-Infrared "Cirrus" (1.37 µm) and Water Vapor (6.7 µm) images, with plots of maximum temperatures on 17 December [click to enlarge]

Topography + Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm), Near-Infrared “Cirrus” (1.37 µm) and Water Vapor (6.7 µm) images, with plots of maximum temperatures on 17 December [click to enlarge]

Southern US storm, and a Tehuano wind event

December 15th, 2018 |

GOES-16 Low-level Water Vapor (7.3 µm) images, 13-15 December [click to play MP4 animation]

GOES-16 Low-level Water Vapor (7.3 µm) images, 13-15 December [click to play MP4 animation]

A large midlatitude cyclone moved from the southern High Plains to the Lower Mississippi Valley during the 13 December15 December 2018 period (surface analyses) — GOES-16 (GOES-East) Low-level Water Vapor (7.3 µm) images (above) showed the evolution of this system.

The corresponding GOES-16 Water Vapor images with plots of hourly surface wind gusts are shown below; peak wind gusts exceeding 50 knots occurred in parts of Colorado, New Mexico and Texas on 13 December.

GOES-16 Low-level Water Vapor (7.3 µm) images with hourly plots of surface wind gusts, 13-15 December [click to play MP4 animation]

GOES-16 Low-level Water Vapor (7.3 µm) images with hourly plots of surface wind gusts in knots, 13-15 December [click to play MP4 animation]

This event was unusually windy in South Texas and the Rio Grande Valley:

Another notable aspect of this storm was a very localized area of heavy snowfall just south of Sweetwater, Texas:


The remnant patch of snow cover was evident in VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) imagery on 14 and 15 December (below). The heaviest snowfall occurred over an isolated ridge along the eastern edge of the Edwards Plateau, where elevations of 2500-2600 feet were about 500 feet higher than the adjacent rolling plains. Since snow is a very effective absorber of energy at the 1.61 µm wavelength, it appeared dark on the Snow/Ice imagery.

Topography, Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images on 14 December [click to enlarge]

Topography plus Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images on 14 December [click to enlarge]

Topography plus NOAA-20 VIIRS Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images on 15 December [click to enlarge]

Topography plus NOAA-20 VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images on 15 December [click to enlarge]

The residual snow cover on 14 December was also seen in Terra/Aqua MODIS True Color and False Color Red-Green-Blue (RGB) images, viewed using RealEarth (below). The snow appeared as shades of cyan in the False Color images.

Terra/Aqua MODIS True Color and False Color images on 14 December [click to enlarge]

Terra/Aqua MODIS True Color and False Color images on 14 December [click to enlarge]

A toggle between Terra MODIS True Color RGB images on the late morning of 14 and 15 December (below) demonstrated the amount of snow melt in 24 hours.

Terra MODIS True Color RGB images on 14 and 15 December [click to enlarge]

Terra MODIS True Color RGB images on 14 and 15 December [click to enlarge]

The strong cold front associated with this storm moved rapidly southward across the western Gulf of Mexico on 14 December (surface analyses), crossing the terrain of the Isthmus of Tehuantepec in southern Mexico and emerging into the Gulf of Tehuantepec as a gap wind (known as a Tehuano wind). A curved rope cloud marking the leading edge of the Tehuano winds was evident on GOES-17 and GOES-16 “Red” Visible (0.64 µm) images (below).

* GOES-17 images shown here are preliminary and non-operational *

GOES-17 (left) and GOES-16 (right)

GOES-17 (left) and GOES-16 (right) “Red” Visible (0.64 µm) images [click to play animation | MP4]

A comparison of GOES-16 Visible imagery from 14 and 15 December (below) showed how far southwestward the gap winds spread out across the Pacific Ocean during those 2 days. Note that on 15 December there were ship reports with wind speeds of 50 knots, at 12 UTC and at 17 UTC.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images with surface and ship reports, 14-15 December [click to play animation | MP4]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images on 14 and 15 December (below) also showed the progression of the Tehuano wind rope cloud — the hazy signature of dust-laden air within the offshore flow was also apparent on the daytime True Color images.

NOAA-20 VIIRS True Color and Infrared Window (11.45 µm) images on 14 and 15 December [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images on 14 and 15 December [click to enlarge]

Metop-A and Metop-B ASCAT surface scatterometer winds across the western Gulf of Mexico [click to enlarge]

Metop-A and Metop-B ASCAT surface scatterometer winds across the western Gulf of Mexico [click to enlarge]

On 14 December, a sequence of EUMETSAT Metop-A and Metop-B ASCAT surface scatterometer winds (source) showed the cold front moving southward across the western Gulf of Mexico (above), and also showed the northerly gap wind flow just beginning to emerge into the Gulf of Tehuantepec around 1607 UTC (below).

Metop-A and Metop-B ASCAT surface scatterometer winds across the southern Gulf of Mexico and the Gulf of Tehuantepec [click to enlarge]

Metop-A and Metop-B ASCAT surface scatterometer winds across the far southern Gulf of Mexico and the Gulf of Tehuantepec [click to enlarge]

The plume of dry air being transported southwestward across the Pacific Ocean by the gap winds was apparent on MIMIC Total Precipitable Water images (below). The majority of this dry air was within the surface-850 hPa layer (21 UTC comparison).

MIMIC Total Precipitable Water product (Total column, and Surface-850 hPa layer) [click to play animation]

MIMIC Total Precipitable Water product (Total column, and Surface-850 hPa layer) [click to play animation]

Severe thunderstorms in Argentina

December 10th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.3 µm, bottom) images [click to play MP4 animation]

A comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the development of thunderstorms well ahead of a cold front (surface analyses) that was moving northward across central Argentina on 10 December 2018. A Mesoscale Domain Sector had been positioned over that region in support of the RELAMPAGO-CACTI field experiment IOP15, providing imagery at 1-minute intervals. The northernmost storm (of a cluster of 3) featured a very pronounced overshooting top that was seen for several hours, briefly exhibiting infrared brightness temperatures as cold as -80ºC (violet enhancement) at 2133 UTC and 2134 UTC. Also noteworthy was the long-lived “warm trench” (arc of yellow enhancement) immediately downwind of the persistent cold overshooting top.

Plots of GOES-16 GLM Groups on the Visible and Infrared images (below) showed a good deal of lightning activity with this convection — especially in the leading anvil region east of the storm core. However, it is interesting to point out that there was a general lack of satellite-detected lightning directly over the large and persistent overshooting top. The GLM Groups were plotted with the default parallax correction removed, so the optical emissions of the lightning aligned with cloud-top features as seen on the ABI imagery.

GOES-16 "Red" Visible (0.64 µm, top) with GLM Groups and "Clean" Infrared Window (10.3 µm, bottom) images [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm, top) with GLM Groups and “Clean” Infrared Window (10.3 µm, bottom) images [click to play MP4 animation]

A similar comparison of GOES-16 Visible and Near-Infrared “Snow/Ice” (1.61 µm) images (below) helped to highlight the formation of multiple Above-Anvil Cirrus Plume (AACP) features, which are signatures of thunderstorms that are producing (or could soon be producing) severe weather such as tornadoes, large hail or damaging winds. The appearance of gravity waves upshear (west) of the overshooting top was also very apparent.

GOES-16 "Red" Visible (0.64 µm, top) and Near-Infrared "Snow/Ice" (1.61 µm, bottom) images [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm, top) and Near-Infrared “Snow/Ice” (1.61 µm, bottom) images [click to play MP4 animation]

Plot of severe weather reports [click to enlarge]

Plot of severe weather reports [click to enlarge]

There were several reports of hail with these particular thunderstorms (above), concentrated in the area between 35-36º S latitude and 62-65º W longitude. GOES-16 Visible images (below) showed this was the area under the path of the more northern storm with the prolonged overshooting top and the prominent AACP. This convection produced very large hail in Ingeniero Luiggi and General Villegas (located at 35.5º S, 64.5º W and 35º S, 63º W respectively) — see the tweets below for photos. On a side note, the large overshooting top began to take on an unusual darker gray appearance after 2230 UTC, possibly suggesting that boundary layer dust or particulate matter was being lofted to the cloud top by the very intense and long-lived updraft — the 18 UTC surface analysis showed that sites northwest of and south of the developing storms were reporting blowing dust.

GOES-16

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

Additional GOES-16 animations of these storms can be found on the Satellite Liaison Blog.

A zoom-in of NOAA-20 VIIRS True Color Red-Green-Blue (RGB) imagery at 1835 UTC viewed using RealEarth  (below) showed the 3 discrete thunderstorms in the vicinity of Santa Rosa.

NOAA-20 VIIRS True Color RGB image at 1835 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB image at 1835 UTC [click to enlarge]

A toggle between NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1835 UTC (below) revealed the cold overshooting tops associated with each of the 3 thunderstorms. Also note the swath of wet soil in the wake of the southern storm, which appears darker in the True Color image and cooler (lighter shades of gray) in the Infrared image.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1835 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1835 UTC [click to enlarge]

A toggle between NOAA-20 VIIRS Infrared Window (11.45 µm) images at 1835 UTC on 10 December and 0555 UTC on 11 December (below) showed the upscale growth into a large Mesoscale Convective System (MCS) that moved northeastward (eventually producing flooding in Rosario).

NOAA-20 VIIRS Infrared Window (11.45 µm) images at 1835 UTC on 10 December and 0555UTC on 11 December [click to enlarge]

NOAA-20 VIIRS Infrared Window (11.45 µm) images at 1835 UTC on 10 December and 0555 UTC on 11 December [click to enlarge]


===== 11 December Update =====

GOES-16

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

On the following day, GOES-16 Visible images (above) showed that additional severe thunderstorms developed across northern Argentina, in the general vicinity of a stationary front (surface analyses) east of Cordoba (SACO). Plots of GLM Groups (below) indicated that these storms produced a great deal of lightning.

GOES-16 "Red" Visible (0.64 µm) images, with GLM Groups plotted in red [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm) images, with GLM Groups plotted in red [click to play MP4 animation]

The corresponding GOES-16 Infrared images, with and without plots of GLM Groups, are shown below. The coldest cloud-top infrared brightness temperatures were frequently colder than -80ºC, even reaching -90ºC (yellow pixels embedded within darker purple areas) from 1946, 1947 and 1948 UTC.

GOES-16 "Clean" Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 "Clean" Infrared Window (10.3 µm) images, with GLM Groups plotted cyan [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images, with GLM Groups plotted cyan [click to play MP4 animation]

A NOAA-20 VIIRS True Color RGB image (below) showed the cluster of thunderstorms east of Cordoba at 1817 UTC.

NOAA-20 VIIRS True Color RGB image at 1817 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB image at 1817 UTC [click to enlarge]

A toggle between NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1817 UTC (below) showed the easternmost storm which produced a tornado at Santa Elena.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1817 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1817 UTC [click to enlarge]



Winter storm affecting the southern Plains to the Mid-Atlantic

December 10th, 2018 |

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly plots of surface weather type [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly plots of surface weather type [click to play MP4 animation]

A large storm produced significant winter weather impacts from the southern Plains to the Mid-Atlantic states during the 07 December10 December 2018 period. GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed the progression of the storm during that 3-day interval.

As much as 10-11 inches of snow fell in the Lubbock, Texas area during 07-08 December. A sequence of  Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (below) showed the snow cover melting from 09-10 December. Snow cover absorbs radiation at the 1.61 µm wavelength, so it appears very dark on those images.

Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared

Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images [click to enlarge]

Portions of northern and northeastern Arkansas received ice accrual of up to 0.5 inches due to freezing rain — those areas with snow and ice on the ground can be seen in a comparison of Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (below).

Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images [click to enlarge]

Significant snowfall resulted across the central Appalachians and Mid-Atlantic, especially for so early in the winter season — 1-minute Mesoscale Domain Sector “Red” Visible (0.64 µm) images (below) revealed embedded convective elements and banding that helped to enhance snowfall rates across that region on 09 December. GLM Groups are also plotted on the images; however, there was no satellite signature of lightning associated with the convective elements until 2130 UTC in north-central North Carolina.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with plots of hourly surface weather type in yellow and GLM Groups in red [click to play MP4 animation]

 

===== 11 December Update =====

GOES-16

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images [click to play animation | MP4]

Once clouds cleared the eastern US on 11 December, the areal coverage of snow cover across the central Appalachians and Mid-Atlantic states could be seen in a comparison of GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (above). Note the darker areas seen on 1.61 µm imagery over parts of eastern Kentucky and also from north-central North Carolina into south-central Virginia: those are areas where the snow cover also received a thin glaze of ice from a period of freezing drizzle/rain.