Auckland, on the North Island of New Zealand, has experienced significant flooding starting on 27 January 2023. MIMIC Total Precipitable Water fields, above, (from this site, or downloadable here) show an atmospheric connection between the deep tropical moisture that is persistent between 5^oS and 20^oS; a filament moves with a cyclonic swirl from 26-28 January. A second region of even more moisture is poised to the north of New Zealand by 0000 UTC 30 January. How unusually wet is this moisture stream? NOAA’s Office of Satellite Products and Observations (OSPO) produces percent-of-normal total precipitable water products, available at this website. The values near New Zealand early on 27 January are around 150% of normal, as shown below.

Values approaching New Zealand on 30 January 2023, shown below, are somewhat larger: closer to 175% of normal.

Himawairi-9 imagery on 26-27 January 2023, shown below, shows persistent convective development in/around Auckland.

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Rain totals can be estimated from Satellite. GsMap, a website maintained by JAXA, produces hourly and daily rainfall maps, and the 24-hour total ending at 1200 UTC on 27 January (from this link) is shown below. A similar image, but for the 24 hours ending at 1200 UTC on 30 January 2023, also shown below, indicates very large accumulations over the ocean to the north of New Zealand.

CMORPH real-time estimates of 24-hour precipitation are available in RealEarth (enter ‘CMORPH’ in the search box at that website, or click this link for the event discussed in this blog post). Values for the 24 hours ending 2359 UTC on 26 January, and for the 24 hours ending on 27 January, below, show values near 100 mm around Auckland for the two days. Values for the 24 hours ending 29 January show heavy rains moving back on to the North Island.

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GOES-18 also views New Zealand. The animation of the Night Microphysics RGB, below, produced by the CSPP Geosphere site shows the deep clouds (in red) associated with the abundant moisture/tall clouds to the north of New Zealand, with a slow southward motion to the cloud mass.

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1-minute Mesoscale Domain Sector GOES-18 (GOES-West) “Clean” Infrared images (above) showed convection — which was focused along a quasi-stationary surface trough axis — that was producing periods of moderate to heavy rainfall across parts of Hawai’i on 28 January 2023. Numerous Flash Flood Warnings were issued by NWS Honolulu during this time, frequently for the island of Maui (where the storms appeared to be back-building at times).

During the daytime hours, 1-minute GOES-18 “Red” Visible images (below) also displayed the Total Precipitable Water (TPW) derived product (in cloud-free areas) — with TPW values as high as 1.5-1.6 inches in the vicinity of the surface trough axis.

GOES-18 “Clean” Infrared Window images which included an overlay of GLM Flash Extent Density (below) showed that these storms produced occasional lighting over the Big Island, Maui and Moloka’i.

The MIMIC-TPW product (below) displayed the plume of moisture that was flowing northeastward across the island chain during te 27-28 January period.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) include time-matched (+/- 3 minutes) plots of SPC Storm Reports, and showed thunderstorms that produced tornadoes and damaging winds across southeast Texas and southwest Louisiana on 24 January 2023. One tornado caused EF3 damage in the Houston, Texas area. This severe convection developed along and ahead of an advancing cold front — and also produced heavy rainfall (image | text), including a new daily record of 4.05″ at Downtown Houston.

A comparison of GOES-16 Infrared, Cloud Top Temperature and Cloud Top Height at 2124 UTC is shown above — cursor sampling (below) showed that the Cloud Top Temperature derived product value was about 1ºC colder than the 10.3 µm cloud-top infrared brightness temperature at that particular time (the Cloud Top Temperature product values are typically 1ºC to 4ºC colder).

1-minute GOES-16 Infrared and Visible images with/without an overlay of GLM Flash Extent Density (below) revealed a series of lightning jumps (rapidly-growing clusters of bright white FED pixels) during the 1854-2319 UTC period — with FED values as high as 414 at 2019 UTC (minutes after a tornado began to produce damage in the Houston area) and 445 at 2110 UTC.  To match the images shown above, a modified version of the default AWIPS infrared enhancement was used which helps to more easily identify brief pulses of thunderstorm overshooting tops — some of which exhibited cloud-top infrared brightness temperatures as cold as -75ºC.

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Two more animations were created over a larger spatial domain than shown above. Here’s is the GOES-16 Mesoscale 2 Sector Band 2 (0.64 µm) from 1620 – 2229 UTC (as an mp4 animation), and here is the same mp4 animation but with GLM 5-minute Flash Extent Density overlain.

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A strength of the Night Microphysics RGB in the tropics is that it’s pretty easy to use it in regions of mostly clear skies to diagnose wind shear, because high clouds will show up as dark red, and low cloud show up as pale pink or cyan (see this annotated image). In the animation above (from the CSPP Geosphere site), low clouds around and to the west of the Samoan Islands are moving towards the west-northwest. High clouds are moving in the same direction: Wind shear values are low. In contrast, in the northeastern part of the domain above, low clouds are (also) moving towards the west-northwest — but high clouds are moving off to the east: Wind shear values are high.

A wind shear analysis from 1200 UTC, below, taken from the SSEC/CIMSS Tropical Weather website (direct link to shear plot) confirms what the Night Microphysics RGB suggests.

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