Tornado outbreak in Illinois

December 1st, 2018 |

GOES-16

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

The largest December tornado outbreak on record for the state of Illinois occurred on 01 December 2018 (NWS St. Louis | NWS Lincoln | NWS Quad Cities). 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the development of supercell convection which spawned the severe weather. in addition to the tornadoes, SPC Storm reports included hail as large as 1.75 inch in diameter and wind gusts of 75 mph.

GOES-16 “Clean” Infrared Window (10.3 µm) images (below) showed that cloud-top infrared brightness temperatures were as cold as -55ºC (darker shades of orange) with the more vigorous thunderstorm overshooting tops.

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images, with SPC storm reports plotted in red [click to play animation | MP4]

Plots of 18 UTC and 00 UTC rawinsonde data from Lincoln, Illinois (below) indicated that the coldest overshooting top brightness temperature of -55ºC seen in GOES-16 Infrared imagery was representative of a height just above the calculated air parcel Most Unstabe (MU) Equilibrium Level (EL).

Plot of 00 UTC Lincoln, Illinois rawinsonde data [click to enlarge]

Plots of 18 UTC and 00 UTC rawinsonde data from Lincoln, Illinois [click to enlarge]

A sequence of MODIS (from Terra and Aqua) and VIIRS (from Suomi NPP and NOAA-20) Visible and Infrared images (below) provided 2 higher-resolution views of the pre-storm environment, plus 3 views during/following convective initiation. Unfortunately, the thunderstorms in Illinois were located along the far eastern edge of the instrument scans in the final 2 images.

Terra/Aqua MODIS and Suomi NPP/NOAA-20 VIIRS Visible and Infrared images [click to enlarge]

Terra/Aqua MODIS and Suomi NPP/NOAA-20 VIIRS Visible and Infrared images [click to enlarge]

Even though the convection in western Illinois was near the limb of NOAA-20 (mis-labelled as Suomi NPP) VIIRS swath at 2007 UTC — degrading the spatial resolution and introducing some parallax error — the coldest detected Infrared brightness temperature (-52C) was still several degrees colder than that detected by GOES-16 (below). The two images are displayed in different projections, but the enhancements use the same color-vs-temperature breakpoints.

Comparison of GOES-16 ABI and NOAA-20 VIIRS Infrared Window images at 2007 UTC [click to enlarge]

Comparison of GOES-16 ABI and NOAA-20 VIIRS Infrared Window images at 2007 UTC [click to enlarge]

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]

Eruption of Mount Veniaminof on the Alaska Peninsula

November 21st, 2018 |
GOES-17

GOES-17 “Red” Visible (0.64 µm) and Split Window Difference (10.3-12.3 µm) images [click to play MP4 animation]

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

Following an eruption of Mount Veniaminof on 21 November 2018, 1-minute Mesoscale Domain Sector GOES-17 “Red” Visible (0.64 µm) and Split Window Difference (10.3-12.3 µm) images (above) showed the volcanic ash plume drifting southeastward over the Gulf of Alaska. During the period 1947-2323 UTC the plume was seen to grow to a length of 200 miles from the volcano summit. Note in the Visible imagery that the 2625 ft (800 m) volcano acted as a barrier to the northwesterly boundary layer winds to create a cloud-free “notch” immediately downwind of Veniaminof.

NOAA-20 VIIRS True Color RGB images viewed using RealEarth (below) highlighted the light brown color of the ash plume.

NOAA-20 VIIRS True Color RGB images [click to enlarge]

NOAA-20 VIIRS True Color RGB images [click to enlarge]

A sequence of retrieved Ash Probability, Ash Height and Ash Loading (source) derived from Terra/Aqua MODIS and Suomi NPP VIIRS data (below) indicated high probabilities of ash content, height values primarily in the 4-6 km range and ash loading exceeding 4 g/m3 at times.

Terra/Aqua MODIS and Suomi NPP VIIRS Ash Probability, Ash Height and Ash Loading images [click to play animation | MP4]

Terra/Aqua MODIS and Suomi NPP VIIRS Ash Probability, Ash Height and Ash Loading images [click to play animation | MP4]

 

Increasing ice concentration in Hudson Bay

November 21st, 2018 |

Sea ice concentration derived from AMSR2 data, 06-21 November [click to play animation | MP4]

Daily sea ice concentration derived from AMSR2 data, 06-21 November [click to play animation | MP4]

After increasingly colder air began moving from eastern Nunavut across Hudson Bay beginning on 06 November (surface analyses), the daily sea ice concentration as derived from GCOM-W1 AMSR2 data (source) began to increase in the northern half of Hudson Bay (above) — especially after 15 November once mid-day (18 UTC) temperatures colder than -20ºF were seen at reporting stations along the northwest coast.

A sequence of daily Terra/Aqua MODIS True Color Red-Green-Blue (RGB) images (source) showed signatures of the increasing of ice coverage.

Terra/Aqua MODIS True Color RGB images, 06-21 November [click to play animation | MP4]

Daily Terra/Aqua MODIS True Color RGB images, 06-21 November [click to play animation | MP4]

A toggle between Terra MODIS True Color and False Color RGB images on 21 November (below) confirmed that much of the northern half of Hudson Bay contained ice — snow/ice (as well as ice crystal clouds) appear as darker shades of red in the False Color image (in contrast to the cyan shades of supercooled water droplet clouds).

Terra MODIS True Color and False Color RGB images on 21 November [click to enlarge]

Terra MODIS True Color and False Color RGB images on 21 November [click to enlarge]

19 November maps of Ice Concentration, Ice Stage and Departure from Normal via the Canadian Ice Service (below) further characterized this ice formation, which was ahead of normal for the central portion of Hudson Bay.

Ice Concentration [click to enlarge]

Ice Concentration [click to enlarge]

Ice Stage [click to enlarge]

Ice Stage [click to enlarge]

Ice Concentration Departure [click to enlarge]

Ice Concentration Departure [click to enlarge]