Himawari-9 temporarily took over for Himawari-8 beginning at 0250 UTC on 13 February 2018, as Himawari-8 underwent a 2-day scheduled maintenance. “Clean” Infrared Window (10.3 µm) images of Category 4 Cyclone Gita in the South Pacific Ocean during the satellite transition is shown above.

Himawari-9 was launched on 02 November 2016.

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Himawari-8 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed Cyclone Gita as it moved toward Tonga in the South Pacific Ocean during 11 February – 12 February 2018. The tropical cyclone reached Category 4 intensity (ADT | SATCON) near the end of the animation period.

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.

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GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the development of severe thunderstorms which produced very large hail in the Córdoba, Argentina area on 08 February 2018. Distinct above-anvil cirrus plumes were evident on the Visible imagery, with pulses of overshooting tops exhibiting Infrared brightness temperatures in the -70 to -80ºC range (black to white enhancement). The hail reportedly began around 1930 UTC or 4:30 PM local time. [Note: there is evidence that large hail produced by the northernmost storm may have set a new world record for size]

The above-anvil cirrus 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. One of the largest hailstones was observed in the western suburb of Villa Carlos Paz.

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).

This hail that fell in Argentina Thursday, more than 7″ across, might be a Southern Hemisphere record. More info: https://t.co/0VqmRZpdnb Image: Victoria Druetta pic.twitter.com/cmdB600mJe

— 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

Large hail-producing storms in #Argentina on 8 Feb – #GOES16 VIS/IR Sandwich – **brought to you by the script make_sandwich.sh pic.twitter.com/hfGKaC37zK

— 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

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The animation above shows visible imagery from GOES-16 (0.64 µm) over Pennsylvania on 8 February 2018.  Northwest flow over the ridges of the Appalachians is causing stable waves clouds that are parallel to the topography.  However, the animation shows point sources over Somerset and Cambria counties — in southwestern Pennsylvania — that are changing the character of the clouds and disrupting the linear cloud features.  The animation of the GOES-16 ABI 1.61 µm “Snow/Ice” channel, below, shows that the point sources are causing glaciation in the clouds.  Glaciated clouds contain ice, and ice strongly absorbs energy at 1.61 µm, so glaciated clouds appear dark.  The point sources, likely smokestacks, are perturbing the flow and likely introducing freezing nuclei into the supercooled clouds.  As a result, supercooled cloud liquid water droplets freeze.  The toggle between visible 0.64 µm and near-infrared 1.61 µm at 1312 UTC and at 1402 UTC suggests that different smokestacks are operating at different times of the day.  Note that later in the animations, mid-level clouds move in that obscure the view of the lowest clouds.

In addition to glaciated clouds, snow on the ground appears dark as well.  Snow on the ground in the Susquehanna River Valley, is very bright in the 0.64 µm imagery, and darker in the 1.61 µm.  The darkest regions over south central Pennsylvania and northern Maryland are likely regions where snowfall was followed by freezing rain:  the layer of ice on top of the snow will absorb 1.61 µm energy more readily than the snow itself.  This chart from the National Weather Service Eastern Region shows ice accumulations less than 0.10″ in that region.

There is a GOES-16 Baseline Product that determines cloud-top phase.  The toggle below, showing imagery 1412 UTC on 8 February, suggests a change from supercooled (bright green) to mixed phase (dark green) to ice (red) in the region.  The 2-km native resolution of the Cloud Phase product (ATBD can be read here) vs. 1-km for 1.61 µm (and 0.5-km for 0.64 µm ) might account for some of the differences between what the 1.61 µm channel suggests over southwestern Pennsylvania and what the Cloud Phase product diagnoses.  (In addition, the GOES-16 Baseline Cloud Phase product has not yet reached Provisional Maturity Status).

So, glaciation of clouds can be induced as shown above by turbulence/freezing nuclei introduced by large smokestacks. The 1-minute animations below shows a region of supercooled clouds from 1515 UTC to 1715 UTC. Note the periodic appearance of hole-punch clouds. In this case, aircraft to/from Chicago O’Hare are likely penetrating the thin supercooled cloud layer, and the passage of the planes is causing glaciation. The clouds within the hole punch cloud are glaciated, and therefore dark in the 1.61 µm imagery: energy at that wavelength is absorbed, not reflected as happens in the visible wavelengths.

Ice in Lake Michigan is visible in the 0.64 µm, but not apparent in the 1.61 µm. Lake Ice and water both absorb 1.61 µm energy. Lake ice reflects 0.64 µm energy.

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