Why the Los Angeles fires are so devastating

Even as firefighters battled to contain multiple blazes in Los Angeles and the surrounding area, the estimated damages already have made the fires the region's worst natural disaster in decades.

How the fires started remains under investigation, but recent weather patterns, as well as the region's unique environmental conditions, helped fuel their spread. Here's what to know about why the fires have been so ruinous.

Why have the fires spread so fast?

Southern California is experiencing a drought. Weather patterns that culminated in the declaration of the La Nina phenomenon on Jan. 9 have diverted Pacific storms away from California and toward the northwest. In addition, unusual atmospheric pressure patterns near Los Angeles have blocked the cool storms that typically arrive from the Gulf of Alaska. The area hasn't had significant rain since April.

Researchers say prolonged winter dry spells are likely linked to warming oceans, which can cause the jet stream — the band of fast-moving winds that affects weather across North America — to wander off its usual track.

One Los Angeles weather phenomenon did arrive on time, however — seasonal Santa Ana winds. These push inland air over California's mountain ranges, with gusts growing warmer and drier as they barrel toward the coast. The winds exacerbated the drought by turning any vegetation in the area crispy and ready to burn, and dead trees and brush in the hills surrounding Los Angeles are now starved of moisture, providing ample fuel for the fires. The area is now contending with hurricane-force gusts spreading the flames.

Why have the fires been so destructive?

The two largest blazes are raging in the affluent Pacific Palisades neighborhood of Los Angeles, and, to the east, in an area that spans the cities of Altadena and Pasadena. These areas typify what experts call the wildland-urban interface — the transition zone where open lands meet human development. Wildfires in these zones can be particularly devastating because houses are often in close proximity to highly flammable shrubs and trees, says Crystal Kolden, the director of the Fire Resilience Center at the University of California, Merced.

Why are the fires hard to contain?

Firefighters are contending with a shortage of water. Hydrants in the Los Angeles area are part of municipal water systems that provide enough water pressure to meet daily needs and fight individual structure fires but not to control a series of blazes of this ferocity and scale.

Firefighter operations have also been hampered by the strong winds, which have grounded firefighting aircraft.