The cold drop (Spanish: gota fría) is a weather phenomenon often occurring in the Spanish autumn. It is experienced particularly along the western Mediterranean and as such, most frequently affects the east coast of Spain. It is a closed upper-level low which has become completely displaced (cut off) from basic westerly current, and moves independently of that current. Cutoff lows may remain nearly stationary for days, or on occasion may move westward opposite to the prevailing flow aloft (i.e., retrogression). The term is also used to describe the meteorological phenomenon associated. In Spain, it appears when a front of very cold polar air, a jet stream, advances slowly over Western Europe, at high altitude (normally 5–9 km or 3–5.5 mi).
If a sudden cut off in the stream takes place, caused by various reasons, like the effect of the high pressures, a pocket of cold air detaches from the main jet stream, penetrating to the south over the Pyrenees into the warm air in Spain, causing its most dramatic effects in the Southeast of Spain, particularly along the Spanish Mediterranean coast, especially in the Valencian Community.
This phenomenon is associated with extremely violent downpours and storms, with speeds of 100–200 km (60–120 mi)/hour, but not always accompanied by significant rainfall. For this it is necessary that the high atmospheric torrential rain instability in the lower air layers to combine with a significant amount of water vapors. Such a combination causes the masses of cold air to rapidly discharge up to 500 liters per square meter in extremely rapid rain episodes. This phenomenon usually lasts a very short time, (from a few hours to a maximum of four days) as it exhausts its water reserves without receiving a new supply.
The clouds are formed in the Atlantic Ocean. The more extreme the difference in temperature, the more water is stored in the clouds. The Cold Drop can produce snow or hail.
This way a great mass of cold air rotates and floats like a drop over a warm area.
- "NOAA's National Weather Service - Glossary". Forecast.weather.gov. Retrieved 2014-03-25.
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