Record levels of Pacific tropical cyclone activity continue

The Pacific Ocean has seen an extremely high number of tropical cyclones during the early part of this season, with several more tropical storms developing over the weekend.

Across the whole Pacific Ocean nine tropical cyclones have formed in the last two weeks. The recent high level of activity is a response to the recent strong episode of the Madden-Julian Oscillation combined with the developing El Niño conditions as described in our previous blog.

Several of the recent tropical cyclones have formed over open ocean and have caused little or no disruption. However, others have either affected land areas or are set to do so this week.

Typhoon Chan-hom passed very close to the coast of China at the weekend, with over a million people having to be evacuated from the Shanghai region. Whilst coastal areas saw heavy rain and powerful waves, they were spared the strongest winds as the eye of the typhoon stayed offshore. Chan-hom brought heavy rain to North Korea with 400mm having been recorded at Kimchaek on the northeast coast.

Typhoon Nangka on 13 July 2015. Image courtesy of The National Institute of Informatics

Typhoon Nangka on 13 July 2015.
Image courtesy of The National Institute of Informatics

Typhoon Nangka has just turned northwards in the west Pacific and looks set for landfall over south-western Japan on Thursday bringing the risk of strong winds, heavy rain and storm surge.

Across the other side of the Pacific, Tropical Storm Dolores looks set to become a hurricane as it runs parallel to the Mexican coast. It is most likely to stay out at sea, but there remains a low possibility that it could turn towards the coast in a few days time.

Pacific records

The recent high levels of tropical cyclone activity have resulted in some remarkable statistics.

  • Seven tropical cyclones (including four major typhoons) occurred in the western North Pacific before the end of May beating previous records.
  • The three tropical cyclones which have formed in the central North Pacific this week formed earlier in the season than any previous tropical cyclone in this region. There have never been three storms form in such quick succession in this region.
  • Eight tropical cyclones have formed across the eastern and central North Pacific so far this year – the earliest in the season this has ever occurred.
  • Across the whole North Pacific there have been 19 tropical cyclones so far this year. Taking into account their strength and longevity this amounts to a record 321% of normal activity for this point in the season.

Atlantic calm

By contrast the Atlantic remains very quiet. Two short-lived tropical storms have formed so far (Ana and Bill), but conditions are not conducive for further development in the near future in the tropical Atlantic:

  • Sea surface temperatures in tropical areas are up to 2°C below normal values
  • Wind shear (which inhibits tropical cyclone development) has been persistently high for several weeks.
  • Sea level pressure has been at record high values in the last month.

The growing El Niño is likely to maintain conditions which suppress tropical cyclone activity in the tropical Atlantic for the foreseeable future. However, some tropical cyclone activity cannot be ruled out – particularly outside of the tropics at higher latitudes where conditions are not as harsh as those described above.

Further Information

Official warnings for the latest tropical cyclones are produced by the Japan Meteorological Agency, the Central Pacific Hurricane Center and the National Hurricane Center. The Met Office routinely supplies predictions of cyclone tracks from its global forecast model to regional meteorological centres worldwide, which are used along with guidance from other models in the production of forecasts and guidance. We also provide updates on current tropical storms on StormTracker and via @metofficestorms on Twitter.

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