* Underground caverns filled to 89.9%, good ahead of winter

* Cold weather could still leave market short of gas

* Floating gas terminals for LNG imports are necessary

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FRANKFURT, Aug 10 (Reuters) - Germany must boost gas supply security in the coming four winters after it was cut off from Russian pipeline exports last year, gas storage operators group INES said on Thursday.

Releasing its latest bimonthly update on its members' scenario planning for the coming winter season, which starts in October, it said: "There is a need for action until winter 2026/27."

"Only after that date will gas usage, based on assumptions made in European 10-year network development plans, fall to such degree that no further infrastructure measures are necessary," it said.

The suggested remedies are more floating import terminals for liquefied natural gas (LNG), three of which are up and running, more gas storage capacity, and more pipeline connections beyond the formerly established east to west routes.

"For the 2023/24 and 2024/25 winters, there is no way around floating LNG terminals," said INES' managing director Sebastian Bleschke.

With underground storage caverns currently 89.9% full at 226.6 terawatt hours (TWh), the sector is well prepared to avoid gas shortages in the coming winter, said INES.

However, extremely cold temperatures could still leave some demand unmatched with supply, should current usage patterns continue. Its worst case scenario saw a supply gap to 7 TWh in January, of 15 TWh in February and of 12 TWh in March 2024.

INES members, which include the Astora company within the Sefe group, VNG Gasspeicher, Uniper, and RWE , command 25% of European Union gas storage capacities.

Daily gas usage up to July fell to 1.2 TWh on a monthly average basis, compared with 3 TWh recorded for March averages, and with 3.4 TWh respectively in last December and February, INES data showed.

INES will switch to monthly monitoring reports in the winter months, which will also include what is left of Russian gas flows into the EU, via Turkey and Ukraine. (Reporting by Vera Eckert, editing by Friederike Heine and David Evans)