Glendale (PDF) - Hazard Mitigation Web Portal - State of California

Natural Hazards Mitigation PlanCity of Glendale, CaliforniaSection 8 – FloodsEl Niño events.El Niño is the name given to a phenomenon that starts every few years, typically inDecember or early January, in the southern Pacific off the western coast of SouthAmerica, but whose impacts are felt worldwide. Briefly, warmer than usual waters inthe southern Pacific are statistically linked with increased rainfall in both thesoutheastern and southwestern United States, droughts in Australia, western Africa andIndonesia, reduced number of hurricanes in the Atlantic Ocean, and increased numberof hurricanes in the Eastern Pacific. Two of the largest and most intense El Niñoevents on record occurred during the 1982-83 and 1997-98 water years. [A water yearis the 12-month period from October 1 through September 30 of the second year. Oftena water year is identified only by the calendar year in which it ends, rather than bygiving the two years, as above.] These are also two of the worst storm seasons reportedin southern California.• Thunderstorms and Monsoons: Another relatively regular source of heavy rainfall,particularly in the mountains and adjoining cities, is from summer tropical storms.Tropical rains or monsoons are infrequent, and typically occur in the summer or earlyfall. These storms originate in the warm, southern waters off Baja California, in thePacific Ocean, and move northward into southern California. Tropical storms that havedropped significant rainfall in the southern California area in the last 100 years or so arelisted in Table 8-2 below. Thunderstorms can occur at any time, but are usually moreprevalent in the higher mountains during the summer. Thunderstorms usually impactrelatively small areas.2006 PAGE 8- 8