Forecasters note an unusual pattern ahead of hurricane season
- No Northern Hemisphere tropical cyclones have formed in 2025 as of May 16, a phenomenon only seen five other times since 1950.
- Unusual wind patterns near the Philippines are suppressing storm formation in the western North Pacific.
- In contrast, the Southern Hemisphere has experienced a busier-than-average storm season.
An unusual pattern has emerged ahead of Atlantic hurricane season: No tropical cyclones have formed anywhere in the Northern Hemisphere in 2025 as of May 16.
This includes all tropical storms, hurricanes, typhoons and cyclones north of the equator in the Atlantic, Pacific and Indian Oceans.
The dry spell is not unprecedented — in fact, something similar happened last year ahead of a devastating hurricane season in the United States.
The slow start has been matched 5 other times (1973, 1983, 1984, 1998, and 2024) in the last 75 years, according to Colorado State University meteorologist Phil Klotzbach. Most of those years ended with below-average seasons for the Northern Hemisphere overall.
On average, he said 3.5 storms typically would have formed by now.
Is this quiet stretch unusual?
Typically the Atlantic, eastern North Pacific and North Indian Ocean are pretty quiet through mid-May, Klotzbach said.
"So, the western North Pacific tends to be the primary contributor to named storm activity this time of year," he told Paste BN.
The quiet in the western Pacific is due to unusual wind patterns near the Philippines. "This wind pattern creates anti-cyclonic flow, which is not supportive for storm formations," he said.
Does this mean anything for the rest of the season?
Klotzbach said that's hard to say. "For example, the average number of Northern Hemisphere named storms in a season is 62. Here are the final Northern Hemisphere named storm totals for the other years that had no named storms through May 16:
- 1973 - 45
- 1983 - 51
- 1984 - 65
- 1998 - 53
- 2024 - 58
"4 of the 5 years ended up with below-average Northern Hemisphere named storms, but 2024 was just slightly below normal," he said.
1973 was an unusually quiet year for storms in the Northern Hemisphere. That year set a record for the latest first storm, Klotzbach said: Ava formed in the eastern North Pacific on June 2 that year.
What about Southern Hemisphere storms?
Unlike the Northern Hemisphere, the Southern Hemisphere has been quite busy during the 2024-25 season (July 1, 2024 - present).
Southern Hemisphere storms include those that threaten locations such as Australia.
He said 31 Southern Hemisphere named storms have formed so far, while the average is 25 named storms through May 16.
What's the forecast for the rest of May?
Meteorologist Ryan Maue, also on X, said that while an early season tropical storm is possible in the Eastern Pacific through the end of May, top weather models show a quiet pattern for the Caribbean and Gulf of Mexico (renamed the Gulf of America by the U.S. government).