Unstable weather to persist for another 8 days – Spring with winter tones until May 4-5

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Unstable weather in the next few days with two depressions, the first which already affected us this Friday and continues this Saturday, the 27th, and the Second which will affect us later in early May

This second depression could condition the weather for around 3 days, between the 1st and 3rd of May, with rain, more snow in the mountains, the possibility of thunderstorms and some wind

We thus predict cold weather for April, occasional rain (and snow, at varying altitudes, but which can temporarily reach 1100-1200m), some occasional thunderstorms on some days, particularly in the afternoon, not expected to be severe – at least for already

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This first depression begins to affect France this Saturday, and will generate circulation favorable to an episode of violent rains – lasting 4 to 5 days – which could cause very serious flooding. However, she was not nominated by Météo-France, despite the expected effects

All this will be accompanied by some wind, which accentuates the thermal sensation – mainly on Saturday, the 27th, and again with the second depression predicted, for the end of the month and the first 2 days of May

On the part of the ECMWF model, we leave, from now on, the animated forecast (GIF) of pressure and geopotential that shows us exactly what will happen – the passage of several disturbances, in a scenario more typical of Winter than exactly the middle of Spring!

UNSTABLE WEATHER – RAIN, COLD, THUNDERSTORMS – SUMMARY UNTIL MAY 3

For this prediction we used a combination of several models, including some “traditional” models and new “machine learning” models. The truth is that they all present somewhat similar predictions, so the prediction is even a little more reliable!

The depressions that will affect us should not be named, as, at the date of the forecast, they do not meet criteria for nomination by any responsible agency. Even so, after affecting Portugal tThey also affect the North of Spain and France, with some intensity, so it is not completely impossible for one of these agencies to name one of the depressions, and this would not alter the forecast in any way.

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In summary, we foresee the following conditions for Portugal

SATURDAY APRIL 27

On Saturday we will have intermittent precipitation, with a special incidence in the afternoonwith showers and possible localized thunderstorms (DO NOT SEVERE), some hail and snow, in the early hours of the morning it could fall to 900m in the North region, something unusual at this time of year, and perhaps 1100 or 1200m in the Center region, rising to 1200 to 1400m in the afternoon
The highest mountains in these 2 days can accumulate up to 5 to 10cm of new snow – very good for this time of year. Fortunately, snow does not fall in the lower lands, nor do we expect frosts these days – unfortunately they may appear in the following days…
We wait for the increase in the intensity of the wind, which starts to blow strongly during the day on Saturday, sometimes with gusts of up to 70km/h on the coast and 80km/h in the highlands, especially in the early morning, and again in the afternoon
The sea may have waves up to 56m on the West Coast

SUNDAY APRIL 28 AND MONDAY APRIL 29

These days we wait open, and maximum temperatures rise slightly
On the other hand the lows drop a little
So it is likely that there will be frosts located in the North and Center Interior, unfortunately
Despite the open, especially on Sunday, in the afternoon, showers are likely, and even thunderstormshail, with snow in the highest points of the mountains (Above 14001500m)
It should be noted that These thunderstorms should not have the same severity as the thunderstorms we had around April 20th, as we have much less energy in the atmosphere – yet the unpredictable dynamics require careful monitoring
Some wind, nothing very relevant, but making the thermal sensation even lower
O sea with some agitation, but calming down a little, waves up to 23m

TUESDAY, APRIL 30 AND WEDNESDAYTHURSDAY, MAY 123

Uncertainty in evolution, but According to most models, we should see the passage of a front on Tuesday, April 30th (rain more consistent in the North and Center, less in the South) followed by showers and thunderstorms on May 1st, with a relatively intense frontal aftermath according to most models

Snow is likely to fall again in the highest mountains

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On the 2nd of May, it is very likely that there will be a new front, with a further increase in the intensity of rain, and a further increase in wind, as well as some sea agitation, which should be followed by a period of showers that will continue until the 3rd. of May, maybe even May 45

To illustrate the prediction we leave the map of total rainfall accumulated for these days using the ECMWF model, and what a beautiful irrigation in the North and Center, especially on the coast, and, despite being a little further south, it is good for maintaining moisture in the soil!

We also leave the snowpack forecast by SnowForecast for the next 3 days

SNOW UNTIL APRIL 30 – FORECAST

SnowForecast Map – snow forecast in more detail for the following days, if necessary, will be updated

Unstable weather to persist for another 8 days - Spring with winter tones until May 4-5

WHAT IS THE ORIGIN OF THIS SITUATION? WHY IS THE WEATHER SO UNCERTAIN?

This air mass originates in Greenland, then descends in a NorthwestSoutheast flow, due to the rise of the Azores anticyclone to the North

You Blocking to the north, which is what we will experience in the coming days, is common when we have a disturbed, weak jet stream. We are still feeling the effects of the sudden warming of the stratosphere in March, which ended up greatly affecting the polar vortex, and we are also feeling the effects of the final warming of the stratosphere, before the summer. Together with the end of El Niño and the transition of seasons make this time of year particularly unstablewith sudden changes (effectively accentuated by climate change) and with extreme

It’s true that we are predicting cold and rain, but that doesn’t mean it will be like this the entire month of May

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We don’t have a forecast yet, so just an example, still without any reliability, but despite the snow now nothing prevents it from being very hot after 5 or 6 days, perhaps close to the record values of the season – this is what we have seen all over the world, sudden and extreme variations, and it is likely to happen here too – but the forecast for May will only be in a few days when there is more certainty!

For now, the graph below should help you understand why this is the case, Always remember that anticyclones rotate clockwise, and depressions the opposite (in the Northern Hemisphere) with H representing high pressure, and L low pressure!

Unstable weather to persist for another 8 days - Spring with winter tones until May 4-5

IS FROSTS VERY LIKELY TO OCCUR?

Unfortunately according to the most reliable model we have, yes, it is likely (ECMWF)

The type of flow promotes humidity, and the temperature appears to be low enough for frost to form on drier days

If we were at our limit a few days ago, this ended up being limited because the soils were hot, and the nights only cooled down later. This is not the case now, we actually have weather that resembles winter

Like this especially on the 28th and 29th, frost is very likely to occur, and then, on other days, depending on whether precipitation occurs or not, it may also occur

In the days 28 and 29 is more likely simply because we predict clearer skies in some places in the Interior and drier weather at night, with night temperatures below those indicated by the AEMET model (Below 5ºC in practically all regions of the Interior, locally even reach close to 0ºC, can even reach negative values in places marked in white)

Unstable weather to persist for another 8 days - Spring with winter tones until May 4-5

AFTER THIS INSTABILITY, WHEN WILL SEASONAL TIME RETURN?

As we have already reported We still don’t have a concrete forecast. The most reliable models indicate a progressive rise in temperature from the 3rd/4th of May, with the installation of the anticyclone, but unstable – that is, probability of thunderstorms, or even the continuation of the passage of more fronts, and variability

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For now seems a credible probability, and it is likely, or even very likely, that around the second week of May we will already have some heat, but we also do not rule out dust, and thunderstorms – the anticyclone is not able to establish itself yet, especially as the blockage in northern latitudes

So the May weather, unstable and hot, is likely to appear – the cold leaves us, the instability not so

However It is necessary to monitor and understand how the anticyclone recovers after this instability – everything still seems to be possible, from a scenario of low temperatures persisting, to a scenario of more intense heat

O The most likely scenario is the one mentioned, hotter, somewhat unstable, and with dust – something that is no stranger to us in recent times

The forecast The GEFS model average does indicate a rise in temperature and instability, but we can see the ensemble lines “in a mess”, which indicates uncertainty. You should wait for the May monthly forecast coming soon for more details, and follow our daily forecasts day by day HERE

Thank you very much for your trust and preference!

Ensemble GFS next few days

FINAL NOTES AND SOURCES USED FOR INFORMATION

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