Musings and forecasts of Andalusian weather and climate, from a veteran meteorologist.
By: esteban9, 7:08 AM GMT on September 26, 2010
Well, it appears that the weak disturbances forming near the Canary Islands and moving over Spain are much weaker than anticipated earlier. So for the coming week, they may bring periods of clouds but no precipitation. Therefore, enjoy the pleasant cooler weather without getting wet!
By: esteban9, 11:17 AM GMT on September 23, 2010
A patch of moderate rain is just clearing the Málaga area. Though most of the heavier showers have been near the Straits, the upper trough is approaching Portugal and is already triggering more widespread coverage of precipitation in the west. Expect this invasion of showers to increase this afternoon and evening.
By: esteban9, 7:23 AM GMT on September 23, 2010
Well, a well-developed "warm conveyor belt" of cloudy air has covered all of Iberia. This cloud band extends well to the west of the Canary Islands and is producing some light showers across Andalucía this morning. By and large, the computer models failed to predict this precipitation.
Nevertheless, this rain should remain on the light side during the day today, in spite of substantial moisture in the atmosphere. Significant rains await the approach of a weak upper-level wave, which will occur during the overnight hours. Although again the models are advertising light precipitation amounts, given the moisture already in place ahead of the wave, there could be some scattered areas of heavier rains. The models are also downplaying instability that would support thunderstorms tonight, but their poor accuracy regarding today's rain means that we should beware the possibility of such storms.
The good news for those who prefer benign sunny weather is that the wave is moving quickly and skies should clear behind it tomorrow late morning. This fair weather will be short-lived, as another weak disturbance arrives early Sunday. In fact, the upper air pattern has shifted to one that favors weak low pressure systems at our southerly latitude, so extended periods of uninterrupted sunshine don't appear on the horizon for at least a week.
By: esteban9, 10:47 AM GMT on September 22, 2010
A cold front approaches Spain from the north, with its arrival anticipated on Friday. While the rain associated with this front should be light and showery in Andalucía (late Thursday and Friday), the main change will be substantially cooler temperatures, ushered in by northerly winds. Sunshine should return on Saturday but highs will be reduced 5-7 degrees.
It appears that high temperatures in excess of 35 degrees are gone for the season, even in the usually warmest inland areas.
By: esteban9, 7:51 AM GMT on September 18, 2010
Well, the thunderstorms that built in the early afternoon yesterday dissipated as quickly as they formed, not leaving much impact on the area. The storms moved quickly away toward northeast Spain after about 5 PM, where they hammered the Barcelona area.
Today and tomorrow will be characterized by much more settled weather, with mostly sunny skies but mild temperatures (highs in the upper 20s). Very pleasant for outdoor activities!
As alluded previously, the next rain is headed our way early Monday. This will be brought to the area courtesy of a weak upper disturbance from the southwest. Again, while precipitation amounts should be light, there will be the threat of thunderstorms on Monday afternoon.
For now, it looks like there'll be no return to the heat that existed prior to the recent storms.
By: esteban9, 12:08 PM GMT on September 17, 2010
Most of Andalucía is covered with convective clouds at present, and several lines of thunderstorms have developed in the west, center and east. Looks like a wild and wooly afternoon coming. Stay away from exposed and open territory, where you are vulnerable to lightning.
By: esteban9, 7:14 AM GMT on September 17, 2010
While well outside Andalucía, the city of Cáceres experienced downpours, hail, and flash flooding late last night (around 2200 hours; see story here). This resulted in numerous cars being washed down the street and damages to property, but no injuries. The cluster of thunderstorms responsible was the one I cited near the Portuguese border yesterday afternoon. The severe storms corresponded well with the coldest pocket of air at mid-atmospheric levels.
Again, today should be the peak precipitation day for Andalucía. While the greatest coverage or rain should shift to the central part, the aforementioned cold pocket will still be to our northwest, so the threat of thunderstorms will remain across all areas. Fortunately, upper flow is strong so the storms will not park themselves over one area; nevertheless, there is a lot of moisture in the atmosphere so localized flooding is still a threat. As usual, the various sierras will be at greatest risk for thunderstorm development. AEMET has issued an important (orange) risk of rain rates up to 30 mm per hour. Even though the upper disturbance is weakening, the event in Cáceres last night indicates that vigilance is warranted, particularly in the afternoon and early evening.
By: esteban9, 4:30 PM GMT on September 16, 2010
There's a line of thunderstorms on the border, with one storm west of Aracena looking intense on the Portugal radar. Will monitor this evening.
By: esteban9, 7:32 AM GMT on September 16, 2010
The cloud band described yesterday is now draped across most of Spain, which will cut down on sunshine and usher in much cooler conditions area-wide. The Gibraltar sounding, which shows substantial dry air below 3 km, combined with a weakening upper disturbance, should mean that the risk of severe thunderstorms will be greatly weakened today. There will be some rain, especially in the afternoon through evening, but torrential downpours will be unlikely. AEMET seems to have caught on with this idea, as they have no alerts in all Spain today. Most of the thunderstorms that do occur will be in the southwest (Huelva, Cadiz areas) overnight, but since instability there won't be aided by daytime heating, I don't expect these to be severe either.
It still appears that tomorrow will see the heaviest and most widespread rain (including scattered thunderstorms)but, as the day progresses, this rain will shift gradually away from Andalucía toward the northern and eastern part of Spain, where a cold front will lie. By Saturday, the region should be dry, partly cloudy and much cooler (highs mainly in the upper 20s). So the weekend will be very pleasant for those who are looking for some sun, but also relief from the recent hot weather.
Another weak upper disturbance looks to follow up the current one, Monday and Tuesday. I don't anticipate much significant rain with that one.
By: esteban9, 9:54 AM GMT on September 15, 2010
By the way, regarding my last entry about the gota fría...The article to which I linked at the bottom explains that the term is outdated and no longer used in meteorological circles, partly because it is confusing and ambiguous. While I agree with the reasoning, once a term becomes ensconced in the public's mind, one has to use a crowbar to remove it. I'm too new to the scene to take sides at this date, but in the future...who knows?
Updated: 9:55 AM GMT on September 15, 2010
By: esteban9, 7:36 AM GMT on September 15, 2010
Satellite pictures reveal a rapidly developing "warm conveyor belt" of cloudiness ahead of the storm now strengthening to the west of Iberia, with the leading edge of cloudiness entering Portugal and Galicia now. The computer models are falling into alignment, indicating that the onset of precipitation will be early in the morning tomorrow in the latter areas. Significant showers and thunderstorms in Andalucía should commence tomorrow afternoon, and develop into widespread coverage on Friday.
A big question will be the intensity and coverage of severe thunderstorms, with torrential rains and hail. With a strong flow of warm moist air from the south ahead of the storm, there will likely be some of this severe weather. A pocket of cold air aloft, which dramatically increases atmospheric instability, does not appear to be as well developed as in the 16-17 August Córdoba province event.
The upper level pattern of that storm resembled a gota fría ("cold drop"), which is a cold pocket of air associated with a slow-moving, isolated low aloft. The gota fría commonly occurs in September and October and produces violent thunderstorms, flooding, and damaging winds, particularly in the Levante (east coast). The reason for this geographic and temporal preference is the existence of very warm waters in the western Mediterranean that, similar to hurricanes, provides greater instability. These types of upper storms also occur in California, producing the few thunderstorms experienced in the southern half of that state. The waters off California, in contrast to the Mediterranean however, are cold...greatly decreasing the intensity of the convective storms.
The disturbance aloft approaching the peninsula now is forecast to be an "open wave," rather than a closed or "cut-off" low of the gota fría type. Therefore, I expect most of the thunderstorms to occur in western Iberia (including the western half Andalucía) and to be less vigorous than with a gota fría. Nevertheless, I will watch the satellite, radar and rawinsonde (weather balloon) data closely for changes.
For more reading on the gota fría, see this technical analysis from a meteorologist friend at AEMET (in Spanish). That's all for today's lesson as it applies to this week's storms!
Updated: 7:40 AM GMT on September 15, 2010
By: esteban9, 1:54 PM GMT on September 13, 2010
If you read my thoughts and analyses of the Córdoba event (the last entry was 27 August), you may wish to look at the following blog and comments. There is a lot of interesting insight, opinion and critique therein, in Spanish.
By: esteban9, 12:35 PM GMT on September 13, 2010
As we near the autumnal equinox on 23 September, the atmosphere appears poised to bring fall-like conditions on cue. The first widespread rains in several months will fall beginning Thursday night and ending on Sunday. So for those planning outdoor activities late week and on the weekend, be prepared for some rain showers and possibly thunderstorms.
The instigator for this unsettled weather is weak low pressure entering Iberia from the southwest. The heaviest and most widespread coverage of precipitation will likely be during the day on Friday. The threat of rain will diminish from Saturday through Sunday, but there will still be showers about, accompanied by breezy winds and considerably cooler temperatures (highs in the upper 20s).
The lack of upper level support for this low pressure system will preclude heavy rain amounts, although we'll have to watch the evolution of atmospheric instability to see if there will be isolated heavy downpours from thunderstorms.
Does this system spell the end of summer-like conditions (say, with highs over 35 degrees)? Too early to tell, but the possibility exists!
Updated: 12:36 PM GMT on September 13, 2010