JMA Himawari-9 Near-Infrared “Vegetation” (0.86 µm) images (above) showed the southwest-to-northeast transect of a hybrid solar eclipse shadow as it moved across the South Indian Ocean and passed over parts of Australia, Indonesia and the West Pacific Ocean on 20 April 2023. A portion of the shadow also moved over Tropical Storm Sanvu in the North Pacific.

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MIMIC Total Precipitable Water (TPW) fields, above, from 0000 UTC on 14 April through 1200 UTC on 17 April show a stagnation in flow in/around the Samoan Islands, starting around 0600 UTC on 16 April. This occurs as a storm develops northwest of New Zealand and a strong push of dryer air moves Equatorward to the east of New Zealand. Total Precipitable water estimates for the Pago Pago radiosonde during this time range from 53 to 63 mm (that is, 2 to 2.5″; 2.5″ is near the usual maximum value in Pago Pago in April as shown here) (animation, created at the Wyoming Sounding site).

Data from NOAA-20 NUCAPS (from this website) also suggest an interruption in the flow over the south Pacific. Tropopause heights around New Zealand (below left at circa 1200 UTC on 16 and 17 April) show higher tropopause heights moving from west to east over New Zealand. However, the region of lower tropopause heights between 150 and 165 ^o W longitude is mostly stationary.

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A strong cold front (surface analyses) was moving eastward from the southern Plains toward the lower Mississippi Valley on 15 April 2023 — GOES-16 (GOES-East) Total Precipitable Water and Lifted Index / Convective Available Potential Energy Derived Stability Indices (above) revealed a broad corridor of moisture and instability ahead of the cold front.

1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) images centered over southwestern Missouri (above) included time-matched (+/- 3 minutes) plots of SPC Storm Reports — which showed thunderstorms that produced hail as large as 4.00 inches in diameter and wind gusts as high as 97 mph in Missouri.

The corresponding 1-minute GOES-16 “Clean” Infrared Window (10.3 µm) images with plots of time-matched SPC Storm Reports (below) indicated that some of the thunderstorm overshooting tops exhibited infrared brightness temperatures in the -65 to -70ºC range (darker red to black enhancement).

As the thunderstorms moved farther northeast, one tornado produced EF1/EF2 damage in Missouri — with another cluster of weak tornadoes in general vicinity of St Louis. 1-minute GOES-16 Visible and Infrared images centered over St Louis are shown below.

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2.5-minute rapid scan (Target Sector) JMA Himawari-9 “Red” Visible and “Clean” Infrared Window images (above) showed Category 4 Cyclone Ilsa as it approached the northwest coast of Australia, eventually making landfall near Port Hedland (station identifier YPPD) just after 1500 UTC on 13 April 2023. Overshooting tops within the eyewall region occasionally exhibited infrared brightness temperatures of -90ºC or colder (shades of yellow embedded within darker purple areas).

A Suomi-NPP ATMS Microwave (183 GHz) image from the CIMSS Tropical Cyclones site (below) displayed a closed eyewall structure at 0543 UTC, with a spiral band extending southward.

A RCM-3 SAR image at 1030 UTC (source) is shown below; the peak SAR-derived radial velocity was 144.36 knots within the northeast quadrant of Ilsa.

Himawari-9 Infrared (11.2 µm) images (below) included an overlay of deep-layer wind shear at 1200 UTC — which showed that Ilsa was moving through an environment of low shear (as it traversed warm Sea Suface Temperatures).

A GMI Microwave image at 1821 UTC (above) and a DMSP-18 SSMIS Microwave image at 2006 UTC (below) revealed that Ilsa’s closed eyewall remained intact for several hours after the storm had moved inland, while maintaining Category 4 intensity (as of 1800 UTC).

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