Is early-season record in Pacific a sign of what's to come in hurricane season?

·7 min read

Tropical Storm Andres developed Sunday and became not only the first-named tropical storm of the year in the Western Hemisphere but also the earliest-ever named storm in the East Pacific. Andres formed just about a month ahead of the average first storm for the basin, which typically occurs June 10, and well ahead of the official start of the season, which begins on May 15.

Following a below-normal season last year, the early season development serves as a reminder not to count the season out even when some factors are stacked against an active year.

The Atlantic hurricane season is forecast to be an active one again this year, which usually makes for sluggish tropical activity in the East Pacific in the same year. However, AccuWeather's long-range forecast team says in its annual hurricane season forecast released this week that the basin has the potential to see a near-average number of tropical storms and warns that residents along the affected coasts shouldn't let their guard down.

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"Even when we've had seasons with less active weather, or in other words, less storms than normal, some storms have been very, very deadly and very, very damaging to coastal sections of Mexico," AccuWeather Hurricane Expert Dan Kottlowski said.

Kottlowski listed the 2008 hurricane season, which saw 18 tropical storms and seven hurricanes, as an example. That year, Mexico saw the landfall of Hurricane Norbert, Tropical Depression Five-E, Tropical Storm Julio and Tropical Storm Lowell.

Hurricane Douglas churned through the eastern Pacific on July 23, 2020. The storm had rapidly strengthened into a major Category 3 storm with maximum sustained winds of 120 mph at that point. (NOAA)

Hurricane Norbert made history as the strongest tropical system to strike the west coast of Baja California Sur in recorded history as it made landfall as a Category 2 hurricane with maximum winds around 103 mph on Oct. 11. At its peak intensity, Norbert had generated maximum winds of 135 mph, a Category 4 hurricane. Even after weakening to a Category 2 hurricane, however, the storm claimed at least 25 lives.

Last season, colder-than-normal waters in the basin's main developmental region created conditions that made it difficult for tropical storms to thrive. The main developmental region is an area between 10 and 20 North latitude and from the west coast of Central America to 140 West longitude where more than 85% to 90% of tropical storms and hurricanes develop in the East Pacific.

"That whole area was very unfavorable [for tropical development] much of last year," Kottlowski said. "That's why we did not have much activity, and the activity that we did have was very, very weak."

The 2020 Eastern Pacific hurricane season saw only four hurricanes, three of which became major hurricanes, though they reached peak intensity far from land. The average number of hurricanes for the basin is eight.

A fisherman walks on the dock as Hurricane Norbert passes through Puerto San Carlos in Mexico's Baja California, Saturday, Oct. 11, 2008. Hurricane Norbert slammed into Mexico's southern Baja California peninsula with torrential rains and screaming winds, forcing scores of people to flee flooded homes. (AP Photo/Guillermo Arias)

Besides comparing total storm numbers to average, meteorologists use another measurement to examine the strength of a season. The ACE Index, short for the accumulated cyclone energy index, is a measurement that factors in a tropical cyclone's intensity by accounting for both its strength and duration. Stronger, longer-lasting storms will score higher than weaker, shorter-lived storms. When the ACE Index totals of each storm in a season are combined, it tells the intensity of the season.

The average ACE Index for the basin is 113, but the 2020 season reached a mere 61 on the ACE Index.

But this year, with the Eastern Pacific moving out of the El Niño phase, or the phase that brings warmer waters to the Eastern Pacific, and into a neutral phase, water temperatures are expected to not get cold enough to stifle tropical development like last year, according to Kottlowski.

This year, AccuWeather forecasters are expecting a total of 14 to 18 named storms, six to 10 of which will become hurricanes. Four of these hurricanes are expected to become major hurricanes. The ACE Index is expected to range between 100 and 130 this season.

"We expect about two to three landfalls on either western coastal sections of Central America or Mexico, more likely in Mexico, so we expect this season to be a bit more active than what we saw last year," Kottlowski said.

A particular area of concern for the basin, and a factor that could play into how many landfalls the western coast of Mexico sees, lies in a pocket of cooler water off the southwest coast of California, which could stick around into the season, according to Kottlowski.

Should the cool pocket linger, it could cause the upper-level wind flow to dip down far enough into the tropical East Pacific to steer storms more toward Mexico. This factor is likely to come into play more toward the latter part of the season, from late September into October, if it remains.

"We could end up with more than three storms or so making landfall, which would be normal for that area," Kottlowski said.

Right next door, the Central Pacific basin is expected to see a season similar to 2020, which spawned only two tropical cyclones. An average year in the basin generates four to five tropical cyclones in a season that lasts from June 1 to Nov. 30. Only two named storms are forecast for the Central Pacific with one expected to strengthen into hurricane strength. No major hurricanes are predicted to form. There's also a low potential for any impact to the Hawaiian islands.

Hurricane Douglas is still fresh on the minds of forecasters, serving as a reminder that while chances may be low, they shouldn't be overlooked. Category 4 Hurricane Douglas tracked into the basin last year in late July, but the storm gradually weakened to a Category 1 storm, the strength it had as it made its closest approach to the Hawaiian Islands. Douglas moved about 30 miles north of the islands on July 26, generating high surf and locally torrential rainfall, but most of its wind and rain remained offshore.

"We could have a storm that could come close to Hawaii, but we think the odds are against it bringing any major impacts," Kottlowski said.

The particular factor that will play a role in staving off tropical storms and hurricanes will be colder-than-normal water around the east and south of the Hawaiian islands. Even in the height of hurricane season, sea-surface temperatures are expected to be near or slightly below normal in those areas.

A police officer with the Honolulu Police Department inspects the sand and debris washed onto a closed portion of Kamehameha Highway, Sunday, July 26, 2020, in Kaaawa, Hawaii. High surf caused by Hurricane Douglas washed the debris onto the highway. (AP Photo/Eugene Tanner)

"Most storms that could affect Hawaii tend to track in from the east or up from the south," Kottlowski said. "And so if you've got cooler-than-normal water temperatures in those areas, more than likely storms are going to fall apart or weaken dramatically before even getting close to the Hawaiian Islands.'"

But he warned that this was not a guarantee the island would not be impacted by a tropical storm or hurricane and to not underestimate Mother Nature.

"Because of the cooler water temperatures, we believe chances of a major impact on Hawaii look low at this point, but it does not divorce you from still having a hurricane plan in place," Kottlowski warned. "You should still be prepared. Again, all it takes is just one storm to cause heavy rainfall or strong damaging winds."

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