Severe weather, the type that can cause property damage and loss of life, can take a variety of forms depending on season and location. But during spring and summer in the northeastern United States, it usually takes the shape of an intense thunderstorm. In addition to thunder and lightning, these storms produce strong winds, heavy rain, hail, and the possibility of a downburst or tornado. Therefore, it is important to understand the difference between the various alerts issued by the National Weather Service. They include advisories, watches, and warnings.
- Advisory: Issued when significant, but not necessarily hazardous, weather conditions are likely to occur. Residents should exercise caution.
- Watch: Issued when dangerous weather conditions are possible over the next several hours. They generally cover a large geographic area. Residents should be prepared to take action.
- Warning: Issued when dangerous weather is imminent or already occurring. They cover a smaller, more specific geographic area. Residents should take action immediately.
Hurricane season in the eastern Pacific begins today.
Tropical cyclones, known as hurricanes in the United States, develop around the globe at different times of the year. In the northeastern Pacific, they tend to form between May 15 and November 30. This early start, compared to the Atlantic, is due to the basin’s warm sea surface temperatures and relatively low wind shear.
While powerful, these Pacific storms are generally not as familiar to Americans as those that form in the Atlantic Ocean or Gulf of Mexico. This is because they rarely make landfall in this country. In fact, it has only happened twice. A hurricane slammed San Diego, CA in 1858 and a tropical storm battered Long Beach, CA in 1939. This low rate of occurrence is attributed to the cold water of the California Current that flows south along the west coast. Nonetheless, Pacific hurricanes can still impact the US.
Developing in the tropics, Pacific storms deteriorate as they travel north to cooler waters and in some cases over the mountains of Mexico. However, their remnants are still laden with moisture when they reach the southwestern US, where they often unleash flooding rains.
East Pacific storms can also cross into the Central Pacific and affect Hawaii. (The dividing line between the two basins is 140°W longitude). One such storm was 1992’s Hurricane Iniki, the worst hurricane in the state’s history. With wind speeds measured up to 145mph, it was rated category-4 on the Saffir-Simpson scale.
On average, the eastern Pacific produces 15 to 16 named storms in any given year. Of those, eight to nine develop into hurricanes with 4 to 5 becoming major hurricanes.