Mesoscale vortices in Oregon and Idaho

December 7th, 2018 |

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

As noted by NWS Boise, a pair of mesoscale vortices were apparent over far southeastern Oregon and far southwestern Idaho on 07 December 2018. A comparison of GOES-17 and GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (below) showed that even with the larger GOES-16 viewing angle (or satellite zenith angle), the features could still be seen rather well.

GOES-17 and GOES-16

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

Topography in feet [click to enlarge]

Topography in feet [click to enlarge]

A look at the local topography (above) indicated that the low altitude quasi-stationary Oregon vortex was located within the Owyhee River valley, just northeast of the Rome airport KREO. With high pressure centered over the Idaho/Montana border (surface analyses), the low-level southerly/southeasterly flow seen in a plot of 12 UTC rawinsonde data from Boise, Idaho (below) was being channeled between the higher terrain surrounding the valley; interactions with that terrain likely caused the Oregon vortex to form. The Idaho vortex was moving toward the northeast — Boise rawindsonde data showed southwest winds at 727 hPa or an altitude of 2700 feet. The 2 vortices wre quite small, having a diameter of only

12 UTC rawinsonde data from Boise, Idaho [click to enlarge]

12 UTC rawinsonde data from Boise, Idaho [click to enlarge]

The pair of vortices likely formed just before or right around sunrise, since there was no signature seen in earlier nighttime MODIS or VIIRS “Fog/stratus” infrared Brightness Temperature Difference (BTD) images {below).

MODIS and VIIRS

MODIS and VIIRS “Fog/stratus” infrared BTD images [click to enlarge]

SpaceX launch of Spaceflight SSO-A

December 3rd, 2018 |
GOES-17 Upper-level (6.2 µm), Mid-level (6.9 µm) and Low-level (7.3 µm) Water Vapor, plus Near-Infrared

GOES-17 Upper-level (6.2 µm), Mid-level (6.9 µm) and Low-level (7.3 µm) Water Vapor, plus Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images [click to enlarge]

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

SpaceX launched a Spaceflight SSO-A mission from Vandenberg Air Force Base (KVBG) in California at 1834 UTC on 03 December 2018. GOES-17 Upper-level (6.2 µm), Mid-level (6.9 µm) and Low-level (7.3 µm) Water Vapor images in addition to Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images (above) showed the hot thermal signature of superheated air from the booster rocket engines, along with a brief cold thermal signature of the booster engine condensation cloud on Water Vapor images. A second hot thermal signature was seen over the adjacent waters of the Pacific Ocean at 1840 UTC as the first stage rocket fired its entry burn to land on a drone ship. Since a GOES-17 Mesoscale Domain Sector was positioned over that region, images were available at 1-minute intervals.

GOES-17 / GOES-16 True Color Composite

November 26th, 2018 |
GOES-17 / GOES-16 True Color RGB composite [click to enlarge]

GOES-17 / GOES-16 True Color RGB composite [click to enlarge]

* GOES-17 imagery posted here is preliminary and non-operational *

A composite of GOES-17 and GOES-16 True Color Red-Green-Blue (RGB) imagery (above) was created by blending a total of 59 north-south swaths — each swath within +/- 23 minutes of “local Noon” (for example, the blue swaths using GOES-16) — during the period beginning at 1115 UTC on 26 November (over the eastern Atlantic Ocean and far western Africa, using GOES-16) and ending at 0200 UTC on 27 November 2018 (over the western Pacific Ocean, using GOES-17). Since the GOES-16/17 ABI does not have a true “Green” (0.51 µm) spectral band, that component of the RGB image is simulated using other Near-Infrared bands.

For perspective, the GOES-17/GOES-16 True Color composite is overlaid on a global “Blue Marble” background (below), which helps to emphasize the total areal coverage provided by the GOES-R constellation.

GOES-17 / GOES-16 True Color RGB composite [click to enlarge]

GOES-17 / GOES-16 True Color RGB composite [click to enlarge]

Notable Northern Hemisphere features seen in the imagery include (1) a pair of strong mid-latitude cyclones in the North Atlantic, (2) a large storm in the Gulf of Alaska with a trailing cold front moving inland along the west coast of North America, (3) two storms in the West Pacific, and (4) convective cloud bands along the Intertropical Convergence Zone (ITCZ) in the tropical Atlantic and Pacific basins (below).

Surface analyses from 12 UTC on 26 November to 00 UTC on 27 November [click to enlarge]

Surface analyses from 12 UTC on 26 November to 00 UTC on 27 November [click to enlarge]

Kudos to Rick Kohrs (SSEC) for masterfully perfecting the blending technique to create these composite GOES images.

Train of standing waves south of Hawai’i

November 25th, 2018 |
GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play animation | MP4]

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play animation | MP4]

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

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) revealed an interesting train of standing waves about 100-150 miles south of the Big Island of Hawai’i on 25 November 2018. With the presence of moisture aloft, the 3 water vapor weighting functions — calculated using the 00 UTC Hilo sounding — were shifted to high enough altitudes to eliminate the sensing of radiation from features in the lower troposphere. There were no pilot reports of turbulence in the vicinity of these standing waves — but they were located outside of the primary commercial air traffic corridors to/from the islands.

GOES-17 “Clean” Infrared Window (10.3 µm) and Near-Infrared “Cirrus” (1.37 µm) images (below) showed that these wave clouds were radiometrically transparent to longwave thermal energy being emitted from/near the surface — note that marine boundary layer stratocumulus clouds could be seen drifting westward within the easterly trade wind flow. As a result, the satellite-sensed 10.3 µm infrared brightness temperatures of the standing wave clouds were significantly warmer than that of the air at higher altitudes where they existed. These standing wave cloud features were, however, very apparent in 1.37 µm Cirrus imagery, along with what appeared to be other thin filaments of cirrus cascading southward overhead. The southward motion of the features seen on Cirrus imagery suggests that they existed at pressure levels of 370 hPa (26,900 feet / 8.2 km) or higher — altitudes where northerly winds were found on the Hilo sounding.

GOES-17 "Clean" Infrared Window (10.3 µm) and Near-Infrared "Cirrus" (1.37 µm) images [click to play animation | MP4]

GOES-17 “Clean” Infrared Window (10.3 µm) and Near-Infrared “Cirrus” (1.37 µm) images [click to play animation | MP4]

A comparison of all 16 ABI spectral bands is shown below. Note that in the longwave infrared bands along the bottom 4 panels, the brightness temperatures are progressively colder (darker shades of green) on the 11.2 µm, 12.3 µm and 13.3 µm images — each of these bands are increasingly affected by water vapor absorption aloft, therefore more effectively sensing the thin layer of higher-altitude standing wave clouds. AWIPS cursor sampling showed the differences in detected brightness temperature at 3 different points along the feature: here, here and here. The increasing sensitivity to radiation emitted from higher altitudes can also be seen in a comparison of weighting functions for ABI bands 13, 14, 15 and 16.

GOES-17 images of all 16 ABI bands [click to play animation | MP4]

GOES-17 images of all 16 ABI spectral bands [click to play animation | MP4]

GOES-15 (GOES-West) Water Vapor (6.5 µm), Infrared Window (10.7 µm) and Infrared CO2 (13.3 µm) images (below) showed that the lower spatial resolution of the legacy GOES Imager infrared bands (4 km at satellite sub-point) was not able to resolve the individual waves as well as the 2-km GOES-17 ABI images . Also, as was seen with the GOES-17 imagery, the 13.3 µm CO2 brightness temperatures of the standing wave clouds were significantly colder (shades of blue) compared to those of the conventional 10.7 µm Infrared Window. The corresponding GOES-15 Visible imagery (0.63 µm) is also available: animated GIF | MP4.

GOES-15 Water Vapor (6.5 µm, keft), Infrared Window (10.7 µm, center) and Infraered CO2 (13.3 µm, right) images [click to play animation | MP4]

GOES-15 Water Vapor (6.5 µm, keft), Infrared Window (10.7 µm, center) and Infraered CO2 (13.3 µm, right) images [click to play animation | MP4]

In comparisons of VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 visualized using RealEarth (below), note the highly-transparent nature of the standing wave clouds on the RGB images; only the earliest 2256 UTC VIIRS 11.45 µm image displayed brightness temperatures of -20ºC and colder (cyan to blue enhancement).

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images at 2256 UTC [click to enlarge]

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images at 2256 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 2336 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 2336 UTC [click to enlarge]

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0028 UTC [click to enlarge]

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0028 UTC [click to enlarge]

Terra (at 2043 UTC) and Aqua (at 2347 UTC) MODIS True Color RGB images along with retrievals of Cloud Phase, Cloud Top Temperature, Cloud Top Height and Cloud Top Pressure from the WorldView site (below) indicated that the standing wave feature was composed of ice crystal clouds exhibiting temperature values of -53ºC and colder (dark purple enhancement) located at heights of 12 km or higher (and at pressure levels at or above 250 hPa). These temperature/height/pressure values roughly corresponded to the upper portion of a layer of increasing relative humidity between 200-274 hPa on the Hilo sounding.

Terra MODIS True Color RGB image and retrievals of Cloud Phase, Cloud Top Temperature, Cloud Top Height and Cloud Top Pressure at 2043 UTC [click to enlarge]

Terra MODIS True Color RGB image and retrievals of Cloud Phase, Cloud Top Temperature, Cloud Top Height and Cloud Top Pressure at 2043 UTC [click to enlarge]

Aqua MODIS True Color RGB image and retrievals of Cloud Phase, Cloud Top Temperature, Cloud Top Height and Cloud Top Pressure at 2347 UTC [click to enlarge]

Aqua MODIS True Color RGB image and retrievals of Cloud Phase, Cloud Top Temperature, Cloud Top Height and Cloud Top Pressure at 2347 UTC [click to enlarge]

However, an experimental CLAVR-x version of GOES-17 Cloud Type, Cloud Top Temperature and Cloud Top Height products (below; courtesy of Steve Wanzong, CIMSS) indicated Cirrus clouds having temperature values in the 210-200 K (-63 to -73ºC) range at heights within the 13-16 km range. These colder/higher values raise the question of whether the wave clouds might have formed and been ducted within the shallow temperature inversion near 15 km on the Hilo sounding.

GOES-17 Cloud Type product [click to play animation | MP4]

GOES-17 Cloud Type product [click to play animation | MP4]

GOES-17 Cloud Top Temperature product [click to play animation | MP4]

GOES-17 Cloud Top Temperature product [click to play animation | MP4]

GOES-17 Cloud Top Height product [click to play animation | MP4]

GOES-17 Cloud Top Height product [click to play animation | MP4]

GOES-17 False Color RGB images (below) vividly portrayed the transparent nature of the high-altitude standing wave cloud feature, which allowed westward-moving stratocumulus clouds within the marine boundary layer to plainly be seen. The RGB components are 1.38 µm / 0.64 µm /  1.61 µm.

GOES-17 False Color RGB images [click to play animation | MP4]

GOES-17 False Color RGB images [click to play animation | MP4]

A coherent explanation of this feature and what caused it to form remains elusive, earning it a distinguished place in the what the heck is this? blog category. Perhaps one clue existed in the winds aloft, as depicted by the NAM at 200 hPa, 250 hPa and 300 hPa (below), which showed northerly/northeasterly flow that was decelerating as it entered a trough axis (the region within the red box). Could this flow deceleration have induced a “reverse flow” which then caused enough weak lift to form the thin standing wave clouds within the aforementioned semi-moist 200-274 hPa layer seen on the Hilo sounding? No other obvious forcing mechanisms were in the immediate area — a slowly-approaching surface cold front was too far north of Hawai’i to have played a role.

NAM Winds at 200 hPa, 250 hPa and 300 hPa [click to enlarge]

NAM Winds at 200 hPa, 250 hPa and 300 hPa [click to enlarge]