January is a month usually associated more with snowstorms than those of the tropical variety, but this week has seen some unusual activity in that regard: A tropical storm formed in the central Pacific, the earliest in the year that has ever happened, and another system in the Atlantic has the potential to join the extremely short list of January storms there.

This rare winter storm activity is being fostered by different natural climate patterns, such as El Niño, that are creating conditions friendly to storm formation, one hurricane expert said.

The official hurricane season for both the Atlantic and the central and northeastern Pacific basins ends on Nov. 30. Historically, there is very little activity after this period because of cooling ocean waters and unfavorable atmospheric conditions. Only three have ever been recorded in the central Pacific in the January to March timeframe. But storms can, and have, formed in the traditional off-season when the right factors come together to give them a push.

Tropical Storm Pali formed on Jan. 7 way out in the middle of the Pacific, more than 1,000 miles southwest of Hawaii (so it is not a threat to anyone on land). The timing of its formation wasn’t the only thing notable about it: It also formed unusually close to the equator, just south of the 5 degree latitude mark. It is the southernmost storm ever to form in that region.

Storms typically don’t form that close to the equator because the Coriolis force is too weak there to make a storm rotate.
 


Pali was able to overcome these obstacles thanks to a combination of a strong El Niño and a phenomenon called the Madden-Julian Oscillation, or MJO, Philip Klotzbach, a hurricane researcher at Colorado State University, said. The MJO is an eastward-moving disturbance of rains and winds that traverses the tropics over a period of about 30 to 60 days.

Klotzbach and a colleague at the National Hurricane Center, Eric Blake, have done research that shows that when the MJO is in a particular phase, it can cause a major uptick in storm formation in the central Pacific. The MJO is in that phase now, and it, combined with El Niño, effectively drove winds that were strong enough to provide the storm with the spin it needed to form.

El Niño provided a boost because it has ushered in sea surface temperatures that are 1° to 2°F (0.5° to 1°C) above normal, providing more fuel for the convection at the heart of the storm. El Nino’s warm waters helped fuel a flurry of storm activity in both the central and northeastern Pacific during the main hurricane season.

Pali strengthened slightly overnight, but is expected to slowly weaken as it moves first northwestward, then southward.

Over in the Atlantic, forecasters have their eye on a stormy area that has a chance, albeit a small one at present, of becoming a tropical or subtropical storm. A subtropical storm only has some of the characteristics of a true tropical storm, but still receives a name like tropical storms and hurricanes do.
 

The tracks of the only five known January tropical cyclones in the Atlantic Ocean.

The tracks of the only five known January tropical cyclones in the Atlantic Ocean.

Klotzbach said that the potential storm is being helped by particularly warm waters off the U.S. East Coast. Those warm waters, in turn, are likely the product of the prevailing atmospheric pattern over the Atlantic Ocean, linked to two particular natural climate cycles there.

Only five named storms have ever been recorded in the Atlantic in January, though it is possible that some were missed before satellites were developed, Klotzbach said. Of those five, two were holdovers from December, while three actually formed in January. (One of the former was Tropical Storm Zeta, the final storm of the record-setting 2005 hurricane season.)

If it does fully develop, the storm will be named Alex, and would be the first storm of the 2016 hurricane season, which doesn’t officially begin until June 1.