Abstract
Abstract. Intense orographic precipitation associated with the Central Range was analysed using data of maximum accumulated precipitation in 24 h, occurring between 1958 and 2010. The 18 selected episodes were associated with a southwesterly tropospheric flow, a low-level jet, and high moisture flux at low levels. The observed moisture flux was higher than 100 (m g(s kg)−1) and the dry and wet Froude numbers were greater than 1. The selected area to study this synoptic situation was Gredos, broad and high range, which is located in the eastern part of the Central Range and generates a leeward orographic shadow. The effect of the Central Range on the spatial distribution of precipitation on the Iberian Peninsula plateau results in a sharp increase in precipitation in the south of the Central Range, followed by a decrease to the north of this range.
Highlights
The factors affecting the development of precipitation are complex and the forecasting of precipitation is difficult, with the use of larger spatial and temporal resolutions (Llasat and Siccardi, 2010)
(2001) reported that the presence of a jet at low levels exacerbates the windward precipitation, in agreement with what was observed in this case, where a southwesterly low-level jet stream of 30 m s−1 was observed crossing the Central Range at the 850 hPa pressure level on 25 November at 00:00 UTC (Fig. 4d) This meteorological situation generated a high moisture flux and had a value of 7.2 m s−1 for the U (1h/1x)q index, clearly higher than the threshold value reported by Lin et al (2001) for the Alps
The synoptic characteristics associated with the cases analysed were a strong southwesterly tropospheric flow, with jet streams at low and high levels, and high moisture contents at low levels
Summary
The factors affecting the development of precipitation are complex and the forecasting of precipitation is difficult, with the use of larger spatial and temporal resolutions (Llasat and Siccardi, 2010). Riesco et al (2013) reported that severe precipitation episodes in the southern Iberian Peninsula may be classified into three types according to moisture flux at the 850 hPa pressure level and the lifted index. All of these studies have analysed precipitation occurring in the same area, and we believe it is necessary to explore other areas of the Iberian Peninsula where heavy precipitation falls. Results indicate that daily precipitation extremes are mostly concentrated over the Mediterranean coast, while over durations from 1 month to 2 years extremes are located in southern and northwest Spain
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