Hourly GOES-18 Hemispheric views, above, from 2140 UTC on 1 December to 2040 UTC on 4 December, (from the CSPP Geosphere site) show the development of a strong system in the Gulf of Alaska. This system is tapping into an airstream rich in moisture that augurs for a wet period along the Pacific Northwest coast. Flood watches and have been issued from western Washington and Oregon. MIMIC Total Precipitable Water fields in December ending at 1500 UTC on 4 December, below, show that some of the moisture in the North Pacific may have been part of the Kona Low that drenched Hawai’i last week.

Airmass RGB imagery from GOES-18, below (from this OSPO site), shows the well-developed cyclone with the characteristic orange signal in the airmass RGB denoting air with a large Potential Vorticity signal (as confirmed in this cross-section from1800 UTC on 4 December, take from this site).

For more information on this event, refer to the websites of the National Weather Service Offices in Seattle, Portand and Medford.

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Tropical Cyclone Michuang has formed in the Indian Ocean. Michuang, which means strength or resilience, is situated in the Bay of Bengal on 2023-12-04. Michuang’s center is currently about 48 km from the east coast of the Indian subcontinent. But the bands of the system have already caused major storm surges in the states of Andhra Pradesh and Tamil Nadu. In cities such as Chennai, India, schools are closing and air travel has been put on a pause. Two fatalities are associated with the flooding and high winds. Thousands have been asked to evacuate. The storm is forecast to make landfall on 2023-12-05 at approximately 12Z and may arrive with gusts as high as 68 miles per hour.

RealEarth provides a global infrared product that has full-earth coverage. Watch an animation of infrared data as Tropical Cyclone Michuang develops over the past 48 hours. At infrared wavelengths, users can watch the system develop and organize into its cyclonic structure.  

Another product that can be used to investigate the moisture in Tropical Cyclone Michuang is the MIMIC Total Preciptable Water product (MIMIC-TPW). MIMIC-TPW uses several sensors operating at microwave frequencies to estimate the total precipitable water field. Taking a look at the product below, Michuang is associated with a large area of high TPW values. It is no surprise that this storm is causing major rains and flooding.

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JMA Himawari-9 True Color RGB images created using Geo2Grid (above) showed the ash-laden (darker shades of gray) volcanic cloud produced by an eruption of Mount Marapi that began at 0754 UTC on 03 December 2023. The final advisory issued by the Darwin VAAC estimated that ash extended to 50000 ft (15.2 km).

A radiometrically retrieved Volcanic Ash Height product from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) indicated that maximum ash heights were in the 14-16 km range.

In addition, the volcanic cloud had high levels of Ash Loading, consisting of particles having a large Ash Effective Radius (below). Significant ash fall occurred in a number of nearby villages.

In Himawari-9 False Color RGB images that incorporated the 8.5 µm spectral band (below), brighter shades of green indicated a mixture of SO2 and Ash within the volcanic cloud.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) + Total Precipitable Water (TPW) images (above) showed severe thunderstorms that developed along a cold front that moved north-northeast across Argentina and Uruguay on 01-02 December 2023. Pulses of thunderstorm overshooting tops occasionally exhibited infrared brightness temperatures in the -85 to -90ºC range (brighter white pixels embedded within black-enhanced cloud regions). North of the advancing front, TPW values were in the 2.0 to 2.3 inch range (lighter shades of violet), while TPW values decreased to the 0.5 to 0.7 inch range (lighter shades of blue) behind the front.

At Montevideo (METAR site SUAA, located along the southern coast of Uruguay), thunderstorms produced a peak wind gust of 54 knots (62 mph) at 1615 UTC on 01 December (below) — along with rainfall of 80 mm (3.15 in) in a 6-hour period, resulting in significant flooding.

Farther to the west over northern Argentina, strong winds from a convective outflow boundary (just ahead of the cold front) produced blowing dust that reduced the surface visibility at Rosario (SAAR), Santa Fe (SAAV) and Parana (SAAP) (below).

Low clouds within the north-northeast moving convective outflow boundary were apparent in GOES-16 True Color RGB images from the  CSPP GeoSphere site (below).

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