A new expanse of unusually warm water has formed over the last few months stretching from Alaska to California.

Researchers say it resembles “the Blob,” a similar warm patch that lingered off the West Coast in 2014 and 2015, disrupting marine ecosystems and hurting salmon returns.

The new expanse of warm water is the second-largest marine heat wave in the area in the last 40 years, second only to the Blob.

Researchers say it has grown in a similar way, in the same area and to a nearly similar size.

“It’s on a trajectory to be as strong as the prior event,” said Andrew Leising, a research scientist at the U.S. National Oceanic and Atmospheric Administration. “Already on its own it is one of the most significant events that we’ve seen.”

“We learned with the Blob and similar events worldwide that what used to be unexpected is becoming more common,” said Cisco Werner, chief science advisor at the NOAA.

The NOAA is adding resources to monitor the new heatwave and will provide information on how the Northeast Pacific Marine Heatwave of 2019 – as it’s been labelled – could affect the marine ecosystems and fish stocks.

The warm water has been kept offshore by cold water welling up from the depths along the coast but that usually wanes in the fall. The marine heatwave could potentially move on shore and affect coastal temperatures. 

“It looks bad, but it could also go away pretty quickly if the unusually persistent weather patterns that caused it change,” said Nate Mantua, a research scientist at the NOAA's Southwest Fisheries Science Center.

As of now, forecasts show the marine heatwave lasting months.

The NOAA points out that the Blob was linked to the largest harmful algae bloom ever recorded on the West Coast, which shut down crabbing and clamming for months. It also stranded thousands of young California sea lions and was a disaster for fisheries.