Hourly estimates of Total Precipitable Water (TPW) from MIMIC, shown above in an mp4 animation (click here for an animated gif), show the Intertropical Convergence Zone (ITCZ, as measured by TPW) over the western Pacific evolving from a linear feature at the start of the animation to one with a significant break near 140^oE – 150^oE longitude. This has occurred as Typhoons Doksuri (moving between the Philippines and Taiwan at the start of the animation) and Khanun (moving south of Japan at the end of the animation) have developed (here is a blog post on the formation of Khanun). Formation of tropical cyclones during the breakdown of the ITCZ is not uncommon (as noted, for example, here, and here). The mp4 animation below (click here for an animated gif) tracks the Upper- and Lower-level water vapor infrared imagery (Himawari-9 Bands 8 and 10 at 6.24 µm and 7.3 µm, respectively) over the same time period.

Himawari-9 Clean Window imagery, below, at 0000 UTC on 24 July (left) and 2 August (right) show little in the way of ITCZ convection between the Equator and 20^oN on 2 August, especially compared to 24 July, over the western Pacific. ITCZ convection does persist to the east of 160^oE longitude. MIMIC TPW fields at those two times (here) also show a similar rearrangement of convective centers.

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Target Sector (2.5-minute interval) JMA Himawari-9 AHI Visible and Infrared images (above) showed Category 4 Typhoon Khanun as it moved just south of Okinawa Island  from 0502-1002 UTC on 01 August 2023. Visible images depicted mesovortces within the eye.

During that 0502-1002 UTC time period, peak wind gusts at the 3 METAR sites located in the southern part of the island were in the 70-78 knot range (below) — and soon thereafter reached 85 knots at Naha (ROAH) and Futenma (farther north, the peak wind gust at Kadena RODN was 76 knots).

Synthetic Aperture Radar (SAR) winds (source) from an overpass of RCM-3 at 0922 UTC (below) did show a swath of strong winds — with speeds in the 80-90 knot range — north and northwest of Khanun’s eyewall, which was beginning to encroach upon the southern portion of Okinawa Island.

ARCHER analysis using DMSP-16 SSMIS Microwave (85 GHz) imagery at 0848 UTC (below) displayed an arc of colder brightness temperatures (shades of orange) just east of the southern end of Okinawa Island.

A larger-scale animation of Himawari-9 Infrared images covering a longer period of time (below) revealed a small amount of trochoidal motion with the eye of Khanun — which is a behavior often seen with stronger tropical cyclones (for example, here and here).

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A George Strait concert at an outdoor stadium (Nissan Stadium) in Nashville, Tennessee was cancelled by a forced evacuation — due to approaching thunderstorms — just before 10 PM local time on 29 July 2023 (0300 UTC on 30 July). GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (above) showed (1) the dissipation and departure of an initial cluster of thunderstorms near Nashville (those storms caused a delay in the start of the concert, with a shelter-in-place warning being issued by stadium officials just before 5 PM local time or 2200 UTC — which was then lifted about 45 minutes later, allowing the concert to begin at its originally-scheduled time), and (2) the development of a new cluster of thunderstorms in north-central Tennessee shortly after 9 PM local time or 0200 UTC, which then approached the Nashville area. The coldest cloud-top infrared brightness temperatures were around -70ºC (brighter white pixels embedded within darker black regions).

GOES-16 Infrared images that included an overlay of GLM Flash Extent Density and contours of Lightning Cast Probability (below) revealed an appreciable amount of lightning activity with these 2 clusters of thunderstorms (which was the primary concern for both the initial shelter-in-place warning prior to the concert start time, and the second shelter-in-place warning that led to the concert cancellation). There was a tight gradient in the contours of LightningCast Probability along the leading edge of the second cluster of thunderstorms as it approached Nashville.   

A time series of LightningCast Probability for Nashville International Airport KBNA (below) includes plots of GLM Flash Counts within a 5 and 10 mile radius of the airport — and showed that LightingCast Probabilities began to increase 30-40 minutes prior to nearby GLM Flash Counts. KBNA is located about 5.5 miles southeast of Nissan Stadium.

Note the “Lightning Advisory” headline that was displayed on the stadium’s big screen as the thunderstorms were approaching at the end of the concert:

Check out this time lapse of the evacuation during the George Strait concert last night at Nissan Stadium. https://t.co/AGiCNs7vR6

(Courtesy: Jamie Watts) pic.twitter.com/ePFXD9osaB

— WKRN News 2 (@WKRN) July 30, 2023

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1-minute Mesoscale Domain Sector GOES-18 (GOES-West) Day Land Cloud Fire RGB, Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.3 µm) and Cloud Top Temperature derived product images (above) showed that the Spoon Fire in in east-central Arizona produced a pyrocumulonimbus (pyroCb) cloud late in the day on 27 July 2023. Cloud-top 10.3 µm brightness temperatures reached the -40ºC pyroCb threshold (shades of blue) at 0043 UTC — and later cooled to a minimum of -50.48ºC (with a corresponding Cloud Top Temperature of -54.11ºC) at 0057 UTC (below).

A plot of rawinsonde data from Flagstaff, Arizona at 0000 UTC on 28 July (below) indicated that the -50.48ºC / -54.11ºC cloud-top temperature values were close to the height of the Equilibrium Level (EL) of a Most Unstable (MU) air parcel.

Prior to producing a pyroCb cloud, the Spoon Fire burned very hot — 3.9 µm brightness temperatures reached 137.88ºC (which is the saturation temperature of the GOES-18 ABI Band 7 detectors) shortly after 2300 UTC, and Fire Power values reached 2842.06 MW at 2334 UTC (below). The Fire Power derived product is a component of the GOES Fire Detection and Characterization Algorithm (FDCA),

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