United States

A man tries to clear a street drain during heavy rains caused by Hurricane Beatriz on Monday June 20, 2011. Authorities closed the ports of Acapulco, Manzanillo and Zihuatanejo as Beatriz brushed Mexico's resort-studded Pacific coast with powerful rains and winds, flooding streets as tourists hunkered down in hotels-AP. (AP Photo/Bernandino Hernandez)

While a near-normal number of named storms is forecast for the 2012 eastern Pacific hurricane season, a greater number of storms may impact the northern part of the west coast of Mexico.

Years of drought have been impacting northern Mexico and the Southwest United States.

There is some hope later this summer for needed moisture to travel farther north from the eastern Pacific. However, while reasonable rainfall will be welcomed, any tropical storms tagging along will bring risks to lives and property with the potential for flooding and strong wind and pounding surf in coastal areas.

The AccuWeather.com Hurricane Center is projecting 15 tropical storms, of which eight will become hurricanes in the eastern Pacific Basin.

Most of tropical systems that form along the west coast of Mexico and Central America in the Pacific tend to drift out to sea and diminish without directly striking land.

While this general rule is likely to be obeyed by Mother Nature this season, a higher number of storms expected to form in the basin and a shift in the weather pattern over the western U.S. could bring a greater percentage of systems onshore on the west coast of Mexico.

While it is impossible to project the number of storms that will make landfall, that number is likely to be up from recent years.

According to AccuWeather.com's Long-Range Experts, headed by veteran meteorologist Paul Pastelok, "We expect El Niño to develop this fall and high pressure in the western U.S. to shift farther north for a time later this summer."

El Niño, the opposite of La Niña, is represented by warmer-than-average sea surface temperatures in the tropical Pacific that can lead to a higher number of tropical systems ranging from tropical depressions to tropical storms and hurricanes.

"High pressure has been situated rather far south in the western U.S. the past couple of years. If it sets up farther north as anticipated, it would open the door for more tropical moisture (pop-up thundershowers) to flow into northern Mexico, as well as the potential for several tropical storms or hurricanes in the mix," Pastelok said.

According to AccuWeather.com Tropical Weather Expert Dan Kottlowski, "The key will be how quickly the influence from El Niño develops and how El Niño and the Pacific Decadal Oscillation (PDO) balance out."

The PDO is an anomaly of northeastern Pacific surface water temperature that often lasts for decades. The PDO is currently in a cold phase. Cold water tends to weaken or prevent tropical systems.

It is also believed that the PDO helps to produce frequent troughs of low pressure just off the West coast of North America. These troughs tend to tear up tropical systems as they move northward.

Last season, only a couple of systems wandered north of Cape Corrientes along the west coast of Mexico: Dora off Baja California and Jova after it moved inland south of the cape.

During 2011, Hurricane Beatriz brushed the coast south of the cape during the middle of June. Later that season, during October, Hurricane Jova plowed ashore.

During the lean 2010 season, Georgette managed to cross the southern tip of Baja California and wander into the Gulf of California during the middle of September.

Both Kottlowski and the Long Range Team do not expect the effects of El Niño to be immediate.

Western Weather Expert Ken Clark expects southern Baja California, Mexico, will have to deal with more tropical activity and that the northeastern part of the Mexico mainland and the Southwest U.S. will receive more rainfall as a result, when compared to recent years.

Based on their analysis, a near-average number of named tropical systems (tropical storms and hurricanes) are forecast for the eastern Pacific basin this season and the season may extend later or be weighted more toward the second half of the season.

We have been in a La Niña and cold PDO phase the past two hurricane seasons, which might explain the below-average number of named systems during the period in the eastern Pacific. During the 2010 season, there was a record low number (eight) named systems. During 2011, there were 11 named systems.

It is impossible to say exactly when and exactly where the greatest impacts will be from the tropical systems this far in advance.

There is still the usual risk of multiple storms grazing the west-central coast of Mexico.

There is at least, based on what we are seeing, the potential for not only needed rainfall in the north, but also the dangers that come with hurricanes making landfall farther north in Mexico.

"While you cannot gauge an entire season just because one system jumped the gun, such as Aletta, a greater number of systems, compared to recent years, may be a loaded gun in itself," Kottlowski stated.

Kottlowski, Clark and Pastelok's Long-Range Team of meteorologists have well over 100 years of combined forecasting experience.