Central Pacific heat spawns record-breaking tropical storm

Thursday, July 9, 2015, 6:02 PM - Tropical Storm Ela - the fourth cyclone in the past week to develop over the Pacific Ocean - has broken the record for the earliest tropical storm to ever form during the Central Pacific cyclone season.

With a "typhoon flashmob" currently churning its way towards Asia, the latest storm to spin up in the Pacific - Tropical Storm Ela, which formed far to the east - has become a new record breaker.

Ela is not a very large or strong storm as of today, Thursday, July 9. It  with maximum sustained winds of around 64 km/h - roughly the equivalent of a weak tropical storm on the Saffir–Simpson hurricane wind scale used to measure cyclones that form over the waters around North America.

What's remarkable about Tropical Storm Ela is that it formed so early in the season compared to what is normally seen in the region of the Central Pacific Ocean.

Unlike the Eastern Pacific Hurricane Season, which runs from May 15 - November 30, the season in the Central Pacific starts later, on June 1. However, except for a few storms that have occurred there outside the season, or tracked into the region after forming further east, it's typically not until mid-July before activity really starts to ramp up. That's when ocean temperatures in the Central Pacific - specifically between 140^o West longitude and the International Date Line - warm up enough for cyclones of at least tropical storm strength to develop.

For example, Tropical Storm Upana developed on July 20, 2000, passing to the south of Hawaii before dissipating. Tropical Storm Barbara formed on June 21, 2001, well before Upana or Ela, however it actually developed in the Eastern Pacific, at 126.5^o West. Only on June 26 did it cross over into the Central Pacific, just as it weakened enough to be demoted to a tropical depression. Other storms have formed earlier in the season as well, however none grew strong enough to advance from tropical depression to tropical storm.

Tropical Storm Wali - the former "earliest Central Pacific tropical storm on record" - spun up on July 17, 2014 in nearly the same location that Ela formed on Wednesday. Now, having developed more than a week earlier than Wali, Tropical Storm Ela is the new record-holder for earliest tropical storm to develop in the Central Pacific during the region's cyclone season.

What's fueling Ela's "early rise"?

A few different factors go into tropical cyclone formation, but the two most important ones are a warm ocean surface - at least 26.5 degrees C - and ample rising air.

For roughly the past six weeks, a travelling weather pattern known as the Madden-Julian Oscillation (MJO) had been promoting more sinking air over the Pacific, which suppressed most, if not all, storm formation over the water.

Due to warmer than normal waters off the west coast of North America - "The Blob" in the Northeast Pacific and the anomalous heat in the Central-Eastern Pacific - and the El Niño that is still strengthening in the waters further south, there is plenty of heat to fuel storms, though.

Credit: Environment Canada, with edits by author

The map above shows sea surface temperature anomalies - how much higher or lower the sea surface temperature is from the normal - showing that the region TS Ela formed is anywhere from 0.5 to 3.0 degrees C warmer than normal. Analysis of actual sea surface temperatures (below) shows that the waters in that region are roughly between 28 and 30 degrees C - more than sufficient for storms.

Credit: NOAA/NESDIS

What are forecasters expecting from Tropical Storm Ela?

Based on the latest observations, Tropical Storm Ela is moving towards the northwest, over the slightly cooler waters to the north of the islands of Hawaii, which should cause the storm to lose strength. Currently, it is projected to weaken into a tropical depression by Friday morning before making its way to the west through the weekend.

Sources: Eric Blake/US NHC | JTWC | NWS CPHC | Environment Canada | NOAA/NESDIS | NASA Earth Observatory