Newsletter Issue 58 (August 2025)

HKMetSoc Talk Series 2025 – Why Polar Climate Matters

Date/Time: 27 September 2025, 14:00 – 16:00
Venue: Yasumoto International Academic Park, CUHK
Application via https://forms.gle/G8po2k51sWrUH6f2A
The event will begin with a 1-hour guided tour of the Jockey Club Museum of Climate Change (MOCC), followed by the lecture ‘Why Polar Climate Matters’.

The Weather of July 2025 – A rainy July with the strike of Wipha

After a very dry first half of the year, more significant rainfall eventually returned to Hong Kong in July 2025, mainly due to the passage of the remnant of tropical cyclone Danas in early July and typhoon Wipha in mid-July, as well as showery activities associated with troughs of low pressure and active southwesterly airstreams in the month. Also, the strike of Wipha necessitated the issuance of the Hurricane Signal No. 10 on 20 July.

Third-warmest July globally as extreme climate events continue

The latest Climate Bulletin by the C3S confirms that July 2025 was +1.25°C above the pre-industrial baseline (1850–1900). It was only the fourth month in the past 25 months with a global-average surface air temperature below the 1.5°C threshold set by the Paris Agreement. “Two years after the hottest July on record, the recent streak of global temperature records is over – for now. But this doesn’t mean climate change has stopped.” said Carlo Buontempo, Director of C3S.

Global seasonal climate update (Aug-Sep-Oct 2025)
During August–October 2025, Niño SST indices in the central Pacific are forecast to decline, with a transition toward weak La Niña conditions a possibility. The Indian Ocean Dipole index is also projected to weaken and shift into its negative phase. SST anomalies in both the North Tropical Atlantic and South Tropical Atlantic are expected to remain near average, while above-normal SSTs in the extratropical oceans are projected to persist.

AI-based limited area model for forecasting of surface meteorological variables

(AI summary) AI global weather models advance rapidly, but high-resolution, data-driven limited area models (LAMs) remain rare. This paper introduces a novel 3 km/1 h resolution AI-based LAM using parallel global-local structures, leveraging global AI forecasts for lateral boundary conditions (LBCs). It runs faster than dynamical models, outperforming them in wind speed but underperforming in temperature/pressure forecasts. The latter can match dynamical models with better LBCs.

Climate pollution is making GPS and communications satellites even more vulnerable to solar storms

Satellites will face greater risks in coming decades during solar-triggered geomagnetic storms because of the effect climate pollution has on Earth’s atmosphere, a new study found. The increasing volume of planet-warming carbon dioxide in the upper atmosphere is likely to make the air less dense, while geomagnetic storms have the opposite effect: The ensuing rapid changes in density as a result could cause serious troubles for satellite operations.

WMO certifies megaflash lightning record in USA

The WMO has established a new world record for the longest lightning flash – an incredible 829 km in a notorious storm hotspot in the United States of America. The megaflash occurred in October 2017, during a major thunderstorm complex. It extended from eastern Texas to near Kansas City – equivalent to the distance between Paris and Venice in Europe. It would take a car about eight to nine hours and a commercial plane at least 90 minutes to cover that distance.

WMO photo competition opens for voting (by 8 September 2025)

WMO’s calendar competition is now open for voting on Facebook or Instagram. A WMO jury of experts selected 75 finalists (because WMO marks its 75th anniversary this year) from hundreds of entries from all over the world. The 2026 WMO Calendar focuses on the impacts of weather, climate, and water on people and livelihoods. The finalists also illustrate the power of nature and the urgent need to protect our beautiful planet from human impacts.

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