Drought persists in California

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  • Figure 1: Forecast rainfall across the United States for the week 3-9 May 2014.

    Figure 2: Difference in snow cover between 2010 and 2014 on the 1 May. (Source: NOAA).

    Figure 3: Temperature anomalies across the US during the winter 2013-14. The warmth in western areas was in stark contrast to the often bitterly cold conditions further east. (Source: NASA).

    Figure 4: Forecast for Los Angeles over the next 7 days using our WeatherPro App. It is likely to stay dry throughout.

  • Drought persists in California
    03.05.2014 13:15

     

    California and much of the south-western United States are in a state of severe drought after one of the driest years on record last year and the continuation of the dry and warm conditions through the winter and into early spring. California and surrounding areas largely rely on rainfall during the winter season for their water supply as the summers are often rather dry and sunny. The drought has become so severe across the area that a state of emergency is in effect with water restrictions commonplace.

    Another major source of water for California is from snow melt off the Sierra Nevada Mountains in the east of the State. The snow-pack over the mountains is currently only at 18% of the long term average for this time of year, due to the very low levels of precipitation over the winter and the fact that persistently high temperatures have led to any early spring melt. With snow melt estimated to account for around a third of the water supply in the state, water supply issues are only going to get worse over the coming months.

    Throughout much of last winter and through this spring, a persistent ridge of high pressure extended up from the south-west across western North America, preventing storm systems tracking in off the Pacific to give much needed rainfall. Temperatures were also several degrees above average, leading to increased evaporation of any available soil moisture and from the surfaces of reservoirs.

    Looking at figure 1, which shows the forecast rainfall for the next week until midnight on the 10th May, it can be seen that no real rainfall is expected across much of western and southern California and the Desert South-west, which happen to be some of the worst hit areas by the drought. It is likely that some of these areas will once again have a week where there is no observed rainfall once again.

    However, there are signs that rainfall amounts may finally increase later this year, although there is a lot of uncertainty. There is increasing evidence that El Nino conditions may develop through the summer, with a pool of warm water extending eastwards across the Pacific. During these episodes, autumns and winters across south-western areas of the United States are often (but not always) wetter than average. However, this is by no means certain and the area is likely to have a difficult few months as authorities try to conserve the ever depleting water resources. It may also be a devastating summer season for wildfires as vast swathes of vegetation have dried out. In fact, a wildfire in the San Bernardino Mountains to the east of Los Angeles burnt over 1000 acres last week.

    You can keep up to date with the weather conditions across California and around the world by downloading our WeatherPro App (available on iOS and Android).

    By: Chris Burton