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.
A longer animation of Himawari-8 Infrared images (below) revealed that the center of Gita moved just south of the main island of Tongatapu. Surface observations from Fua’Amotu (NFTF) ended after 0735 UTC.MIMIC-TC morphed microwave imagery (below) showed that Gita underwent an eyewall replacement cycle after moving to the southwest of Tongatapu — a small eyewall was replaced by a larger eyewall, which was very apparent in DMSP SSMIS Microwave (85 GHz) images at 1533 and 1749 UTC.
Metop ASCAT scatterometer surface winds (below) showed Gita around the time that the storm center was just south of Tongatapu at 0850 UTC.
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
Looking farther to the east-northeast over the Atlantic Ocean, a pair of warm thermal anomalies — likely from the recently-separated twin Side Core booster engines (left) and the still-active single Center Core booster engine (right) — were seen on the corresponding 20:47:28 UTC GOES-16 Upper-level (6.2 µm), Mid-level (6.9 µm) and Low-level (7.3 µm) Water Vapor images (below). A similar warm signature in Water Vapor imagery was observed following a previous SpaceX rocket launch in March 2017.While Shortwave Infrared (3.9 µm) imagery is useful for detection of thermal anomalies associated with wildfires or volcanic eruptions, in this case the warm signature (darker gray) was much less distinct compared to what was seen on the water vapor imagery (below).
Plots of weighting functions for the three GOES-16 ABI Water Vapor bands (7.3 µm, 6.9 µm and 6.2 µm) are shown below, calculated using rawinsonde data from Green Bay, Wisconsin and Gaylord, Michigan. With cold air and low values of Total Precipitable Water at these 2 sites (1.53 mm / 0.06 in and 1.88 mm / 0.07 in, respectively), the height of their weighting functions was shifted to significantly lower altitudes compared to what would be observed in a standard atmosphere. This enabled the contrasting thermal signature of the land/water boundaries to easily reach the satellite sensors, passing through what little moisture existed within the atmospheric column. While the peak of the violet 7.3 µm weighting function plots descended to the 879 hPa pressure level at both sites (which was approximately 1.2 km above the surface), a significant contribution could be seen originating from the surface itself.Note that the peaks of the blue 6.9 µm weighting function plots were also anomalously low, reaching the 802 and 754 hPa pressure levels — however, in contrast to the 7.3 µm plots there was very little contribution from the actual surface, and the presence of secondary peaks at higher altitudes led to some absorption and subsequent re-emission of upwelling radiation by that layer of colder moisture aloft. As a result, only the faint outline of Lake Superior and its lake effect clouds were occasionally seen on Mid-level 6.9 µm Water Vapor imagery (below).
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.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.
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).