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Volume 13 Issue 3 May 2024
WRI 2024 West Pacific Tropical Outlook
Jacob Brendel, Meteorologist

As we head into the summer months, tropical activity in the West Pacific Basin will gradually increase. While the official tropical season runs throughout the year, tropical cyclones typically form between May and November.   On average, the West Pacific annual experiences an average of 26 tropical storms, with 16 of these strengthening into typhoons.  For 2024, we are forecasting for near to slightly below average season, though more active than last year.  The transition in the El Niño Southern Oscillation (ENSO) from El Niño condition to a La Niña condition by the fall will play a significant role into how the season evolves. 

What is factoring into a slightly below average season for 2024?

1) A Late Start: Drier than normal conditions across the tropical Pacific for the first half of the season.  The below chart depicts mean monthly precipitation anomalies for the 3-month period from June through August. We note that below average squall development is forecast between 05N-15N east of the Philippines.  This is the main formation region in the West Pacific.  As of May 23rd, no systems have developed yet in 2024, though a disturbance east of the Central Philippines was showing potential. This season will fall into the top five for slowest starts on record. 

Figure 1: Three-month precipitation departures from average for June, July, and August.

 2)  Transition from El Niñto La Niña:  Tropical activity is typically suppressed over the West Pacific when La Niña conditions are in place, though the correlations are not as strong in comparison to its effect on the East Pacific and North Atlantic tropics.  Historically, tropical systems overall occur less frequently and are weaker during La Niña seasons, but higher than normal activity occurs over the South China Sea. 

3) A turnaround is expected:  Higher than normal squall potential over the extreme West Pacific and through the South China Sea during the latter half of the season.  This will be attributed to the development of La Niña conditions in the East Pacific. Secondly, above average sea surface temperatures may counteract the effects of La Niña east of the Philippines.

Figure 2: Three-month precipitation departures from average for September, October, and November. 


 When and Where can we expect Tropical Development?

Referencing the below track map, trade through the busy shipping lanes of the South China Sea through Taiwan will need to be monitored extra closely during the latter half of this season. Depending on the severity and speed of the track of these systems, alternate wider routing to east of the Philippines may be necessary to avoid lengthy stoppages to and from Singapore.

WRI and their team of meteorologists will continue to work hard to keep you informed of any tropical threats affecting the busy shipping lanes across the West Pacific.   Dolphin Online’s Tropical Tracker and basin wide summaries typically provide a week’s notice for possible tropical storm formation. This along with our suite of weather information will help keep you and your team well informed of any concerns.

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