Mutli-spectral retrievals of Ash Cloud Height (below) indicated that the explosive eruption injected volcanic ash to altitudes generally within the 12-18 km range, possibly reaching heights of 18-20 km. Advisories issued by the Darwin VAAC listed the ash height at 45,000 feet (13.7 km).Ash Loading values (below) were also very high within the high-altitude portion of the plume. The Ash Effective Radius product (below) indicated that very large particles were present within the plume immediately downwind of the eruption site. In a comparison of Himawari-8 “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.4 µm) images (below), note the very pronounced warm thermal anomaly or “hot spot” (large cluster of red pixels) on the 0150 UTC image — Himawari-8 was actually scanning that location at 01:54:31 UTC, just after the 0153 UTC eruption. Prior to the main eruption, beginning at 0120 UTC a very narrow volcanic cloud — likely composed primarily of condensed steam — was seen streaming rapidly southward from the volcano summit. The coldest Himawari-8 cloud-top infrared brightness temperature was -73 ºC at 0300 UTC, which roughly corresponded to an altitude of 15 km on the nearby WIMM Medan rawinsonde data at 00 UTC (below). A Terra MODIS True-color RGB image viewed using RealEarth is shown below. The time of the Terra satellite overpass was 0410 UTC. An animation of Himawari-8 True-color RGB images can be seen here.
A longer animation of Himawari-8 Infrared Window (10.4 µm) images (below) revealed a very large convective burst as Kelvin meandered near the coast early on 17 February — periodic cloud-top infrared brightness temperatures of -90 ºC or colder were seen. After making landfall, the eye structure eventually deteriorated by 18 UTC on 18 February.The MIMIC-TC product (below) showed the development of Kelvin’s compact eye during the 17 February – 18 February period; the eye was well-defined around the time of landfall (2147 UTC image on 17 February), and persisted for at least 18 hours (1556 UTC image on 18 February) until rapidly dissipating by 21 UTC. Himawari-8 Deep Layer Wind Shear values remained very low — generally 5 knots or less — prior to, during and after the landfall of Kelvin, which also contributed to the slow rate of weakening. In addition, an upward moisture flux from the warm/wet sandy soil of that region helped Kelvin to intensify after landfall; land surface friction was also small, since that portion of Northwest Australia is rather flat. The eye of Cyclone Kelvin could also be seen in Terra MODIS and Suomi NPP VIIRS True-color Red-Green-Blue (RGB) images, viewed using RealEarth (below). The actual times of the Terra and Suomi NPP satellite overpasses were 0154 UTC and 0452 UTC on 18 February, respectively.
GOES-16 “Red” Visible (0.64 µm) images showed ice motion in the western Great Lakes (above) and the central/eastern Great Lakes (below) on 14 February 2018. A flow of southwesterly winds at the surface was helping to move the lake ice toward the northeast. With increasing winds and a return of warmer air, the ice coverage of Lake Superior, Lake Michigan and Lake Huron had decreased slightly from their seasonal peaks a few days earlier — while the ice coverage for Lake Erie remained neared its seasonal peak. The total ice coverage for the Great Lakes as a whole was 57.9% on this day.
Closer views of southern Lake Michigan and southern Lake Huron are shown below. In Lake Huron, small ice floes can be seen breaking away from the land fast ice.
250-meter resolution Terra and Aqua MODIS True-color Red-Green-Blue (RGB) images from the MODIS Today site (below) provided more detailed views of the ice floes in southern Lake Michigan, southern Lake Huron and western Lake Erie. The Aqua satellite overpass was about 90 minutes later than that of Terra.
The above-anvil plumes could also be seen in GOES-16 Near-Infrared “Snow/Ice” (1.61 µm) images (below).An Aqua MODIS True-color Red-Green-Blue (RGB) image viewed using RealEarth (below) showed the thunderstorm just west of Córdoba around 1850 UTC. According to the Worldview site, the coldest Aqua MODIS cloud-top infrared brightness temperature at that time was -78ºC (below). A time series plot of surface observations at Córdoba (below) showed the warm temperatures and high dew points prior to the arrival of the thunderstorms; there were a number of hail reports between 19 UTC and 02 UTC (4 PM to 11 PM local time).
— Capital Weather Gang (@capitalweather) February 10, 2018
D'autres photos très impressionnantes de grêlons géants le 8 février à Villa Carlos Paz, #Argentine, province de Cordoba
On peut estimer un diamètre de 10-15 cm sur ces photos#grêle #hail #granizo #Argentina
source : fb Rodrigo Contreras Lopez https://t.co/ycY7HvqqKG pic.twitter.com/r7ZuMxE6PV
— Etienne Kapikian (@EKMeteo) February 11, 2018
— Dan Lindsey (@DanLindsey77) February 10, 2018
There were some interesting hail reports out of Córdoba, Argentina on Thursday. Here’s the 12Z sounding, (heavily) modified for 18Z.
Pretty good CAPE, but much less shear than I’d expect for giant hailstones. I’m guessing just enough to develop supercell structures. pic.twitter.com/aiXsao5jL3
— Tim Supinie (@plustssn) February 10, 2018
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.Magnified sections of the Landsat-8 RGB image swath are shown below, moving from northeast to southwest. 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).
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).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.
An Aqua MODIS True-color Red-Green-Blue (RGB) image viewed using RealEarth (below) showed the dense lower-tropospheric smoke drifting southward and southeastward from the fire source region, as well as the narrow upper-tropospheric anvil of the pyroCb cloud. Suomi NPP VIIRS fire detection locations are plotted as red dots on the final zoomed-in image. The actual time of the Aqua satellite pass over Argentina was 1812 UTC.According to Worldview the coldest MODIS Infrared Window (11.0 µm) cloud-top brightness temperature was -41.2 ºC, thus surpassing the -40 ºC threshold that is generally accepted to classify it as a pyroCb. This is believed to be the first confirmed pyroCb event in South America.
Approximately 120 km north-northeast of the pyroCb cloud, rawinsonde data from Santa Rosa, Argentina (below) indicated that the -41 ºC cloud-top temperature corresponded to altitudes in the 10.8 to 11.6 km range. The air was very dry at that level in the upper troposphere, contributing to the rapid dissipation of the pyroCb cloud material as seen in GOES-16 imagery.48-hour HYSPLIT forward trajectories originating from the center of the pyroCb cloud at altitudes of 7, 9 and 11 km (below) suggested that a rapid transport of smoke over the adjacent offshore waters of the Atlantic Ocean was likely at those levels. On 30 January, Suomi NPP OMPS Aerosol Index values (below; courtesy of Colin Seftor, SSAI at NASA Goddard) were as high as 4.3 over the South Atlantic (at 41.81º South latitude, 53.22º West longitude, 17:31:34 UTC) — consistent with the HYSPLIT transport originating at 7 km. Additional Suomi NPP VIIRS True-color and OMPS Aerosol Index images can be found on the OMPS Blog.
===== 01 February Update =====
This analysis of CALIPSO CALIOP data (courtesy of Mike Fromm, NRL) suggests that the upper-tropospheric smoke from this pyroCb event was transported as far as the eastern South Atlantic Ocean by 02 UTC on 01 February, having ascended to altitudes in the 9-10 km range.
Multi-spectral retrievals of the Ash Cloud Height (below) indicated that the ash reached altitudes of at least 10 km (dark blue).A plot of rawinsonde data from nearby Legaspi at 00 UTC on 22 January (below) indicated that the 10 km altitude corresponded to a pressure of 285 hPa. A Suomi NPP VIIRS True-color RGB image from RealEarth (below) revealed some of the lower-altitude ash (shades of tan to brown) drifting toward the west at the satellite overpass time of 0507 UTC. Thermal anomalies — signatures of hot lava flows — are indicated by red dots.
A toggle between 250-meter resolution Terra MODIS True-color and False-color Red-Green-Blue (RGB) images from the MODIS Today site (below) provided a more detailed view of the Lake Erie ice dam and upwind drift ice at 1615 UTC. Snow and ice appear as shades of cyan in the False-color image, in contrast to supercooled water droplet clouds which are shades of white.The Terra MODIS Visible (0.65 µm) image with an overlay of RTMA surface winds (below) showed the southwesterly flow across the long axis of the lake. A toggle between 1607 UTC Terra MODIS and 1757 UTC Suomi NPP VIIRS Visible images (below) showed the motion of the lake drift ice during that time period.
GOES-16 “Red” Visible (0.64 µm) images (below) showed some of the features which helped produce heavier rainfall and snowfall during the daylight hours on 09 January.The circulation of the upper-level low was easily seen on GOES-16 Mid-level Water Vapor (6.9 µm) images (below).
===== 10 January Update =====On the following day, a toggle between Suomi NPP VIIRS True-color and False-color Red-Green-Blue (RGB) images from RealEarth (above) showed (1) the large burn scar from the Thomas Fire (shades of reddish-brown), and (2) snow cover in the higher terrain (darker shades of cyan) on the False-color image. The True-color image revealed sediment from runoff flowing into the nearshore waters from Santa Barbara to Oxnard (shades of brown to light green).
A closer look at the Thomas Fire burn scar was provided by 30-meter resolution Landsat-8 False-color RGB imagery (below), which showed thin filaments of muddy sediment just offshore, as well as fresh snow cover (shades of cyan) along or immediately adjacent to the northeastern edge of the burn scar (in the Hines Peak area). On 10 January, the fire was listed as 92% contained (100% containment was declared on 12 January).
===== 11 January Update =====A comparison of Suomi NPP VIIRS True-color RGB images on 10 January and 11 January (above) showed that sediment was flowing farther offshore from the Thomas Fire burn scar area.
Farther to the south, offshore sediment transport was also seen in the San Diego area (below).