Malaga Weather - 16 Nov 2005 ...The Rain in Spain

The weather on the Costa del Sol on Monday (14th November) brought a sharp reminder that for many places along the Mediterranean coast, November is normally the wettest month of the year.

When the Rain Falls
There are two predominate sources of rainfall in southern Spain during the autumn months. Firstly, as the cross-Atlantic airflow becomes stonger as winter approaches, weather fronts generally become more active with rain-bearing systems penetrating to increasingly low latitudes. However, the sheltered aspect of the Costa del Sol rarely lends itself to much impact from these depressions moving across Iberia from the Atlantic..

Secondly, if deep cold air from far northern latitudes reaches the Mediterranean, the relatively high sea temperatures can act to boost convection considerably and lead to some very heavy rainfall, and occasionally catastrophic flooding. The weather of the 13th and 14th November 2005 fell into this second category, but fortunately the heavy rain was generally welcomed with most problems it caused minor in nature.

The Early Signal
The synoptic analysis for midnight 12th November (see below) shows an active cold front sweeping across northwest Europe followed by cold air originating from within the arctic circle. Ahead of the front, it was fairly warm with temperatures on the Costa del Sol during the day on 13th reaching a pleasant 19 to 21 Celsius (66-70F). There were some well-scattered showers associated with the remnants of an old front that had stalled east of Malaga, but most of the day was sunny.

Surface Analysis for 00 UTC 12th November 2005

Evolving Situation
By midnight on the following night (13th) the surface analysis(see below) had changed significantly. Deep cold air had pushed down the western fringe of Europe with the main area of low pressure pushing cold air east into Scandinavia. In between, pressure built rapidly. An area of low pressure became apparent close to Valencia (Spain), formed as a result of lee troughing in the brisk northwesterly airflow, to the east and south of the Spanish meseta and the Pyrenees respectively; but also due to the increasing temperature contrast between the rapidly cooling land and the warm waters of the western Mediterranean.

Surface Analysis for 00 UTC 13th November 2005

The Beginning of the Event
In the upper atmosphere a sharp trough became cut off over the western Mediterranean with this new upper vortex drifting slowly southwest . Near-surface air became increasingly unstable and the cooling aloft led to vigorous convection breaking out over the warm seas. With the vortex to the east, the Costa del Sol stayed largely dry until late on the 13th when the upper vortex, along with the now coincident surface low, passed across southern Spain to be south of the Algarve by midnight on the 14th (See below)

Surface Analysis for 00 UTC 14th November 2005

The Rainy Day
The first rain of any significance arrived along the Costa del Sol in the early hours of the 14th. It can be seen in the satellite sequence below that a trough moved eastwards over southern Spain, spawned by the obvious vortex positioned close to Cadiz. Thunder was heard widely along the coast between 0200 and 0400 UTC with rainfall rates locally exceeding 60mm/hr. Another trough moved east during the early evening, and although the spell of rain was short-lived , rates exceeded 80mm/hr with several loud claps of thunder.

In the images above, widespread convective cloud tops are apparent over the sea and adjacent coasts from Marseilles to the Costa Brava, as well as the northern part of the Costa Blanca and across to Ibiza is apparent. Deep cold exists of the Moroccan coast with several cumulonimbus clouds over the relatively cool waters in this part of the Atlantic Ocean.

The Stabilisation
During the evening of the 14th, it became obvious from satellite images (see below) that the air was stabilising from the north as pressure built across western Europe. The short episode of unsettled weather was over but the rain it brought to Spain was much appreciated.

Statistics of the Event
Rainfall totals in the 24 hours up to 1800 UTC on the 14th were as follows: Valencia 27mm; Ibiza 28mm; Alicante 6mm; Almeria 1mm; Murcia 4mm; Granada Trace; Malaga Airport 29 mm; Malaga Beach 26 mm; Jerez 31mm; Cordoba 9 mm; Faro 2mm; and Gibraltar 33mm.

It can be seen from the rainfall values above that the heaviest rain was generally concentrated around the coasts, although the coast around Almeria unsurprisingly maintained its reputation as the gateway to the 'desert' of Europe. Granada Airport (567m above sea level) also had very little rain on the 14th, but the temperature in the evening fell to 5 Celsius (41F) in drizzle, and 11 mm on the following day was useful, and at higher levels around 5 cm of snow fell on the skiing areas in the Sierras. How long the snow lasts in the mountains remains to be seen, but for the coast of southern Spain, spring-like weather had returned by the 17th with temperatures climbing to 21 Celsius (70F) under clear blue skies.

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