Weather forcast advice

Here 10 advices by Luca Mercalli, the most famous weather forecaster in Italy!

1. WEATHER FORECASTS ARE NOT A CERTAINTY

The weather forecast are not a certainty, otherwise they would not call like that. Instead of this, meteorology  has made progress in last decades and now is a mature and international science, which every day test itself to a very widespread public.

2. A RELIABLE FORECAST DOESN’T GO BEYOND 3-5 DAYS

A reliable forecast doesn’t go beyond 3-5 days; but the mathematical models work information until about 10 days, with no sufficient reliability  to the need of everyday life. Not trust in sources that spread detail forecasts beyond a week. Beyond 2 days it can be expected a general idea of the situation  but it’s good to control gradually more recent forecasts, in order not to be condicionated by one in the meantime changed. The weather forecast is like milk: expires soon!

3. THE PROBABILITY OF SUCCESS OF A WEATHER FORECAST REACHES 90%

Now the probability of success of a 24hours-weatherforecast about raining presence – absence reaches 90%, a high value, but it means that in a year there are at least 36 days of wrong forecast: and if they happen during weekend, they be more noticed. For the second day the probability of success is lower, around 80% and decreases beyond the third day. Foresee good weather for several days during a wide anticyclone (high pressure) is more reliable than to foresee phenomenon in a cyclonic situation (low pressure).

4. IT IS PRATICALLY IMPOSSIBLE TO FORESEE STORMS DURING SUMMER

Just the favorable situation for their development can be foresee, but not their exact place and intensity. During winter the level of the snow is the most uncertain element: it can be vary about a hundred meters from the expected altitude.

5. THE SUCCESS OF A FORECAST DEPENDS ON THE NEED OF THE USER

It’s one thing if the expected weather is meant in a like a big city for all day, but it’s another thing if we mean the weather in a birthday party in the garden at 3 pm. Generally it is easy to foresee the good or worse weather, in another hand the effects of weak disturbances are more uncertain.

6. NOT EVERY FORECATS ARE RELIABLE

Regional and national services, paid by our taxes, commercial or amateur web sites having different aims insted of weather information, like advertising.

7. IN ITALY LOCAL WEATHER FORECAST SERVICE ARE AUTHORITATIVE

In Italy, beyond Aeronautica Militare, local weather forecast service are authoritative and they know better the climatology of territory, but they are shattered at regional level. The weather forecast services of all around the world are coordinated by Word Wide Weather Forecast Organization, agency of ONU with seat in Ginevra: www.wmo.ch

8. THE WEATHER FORECASTS “WITH ICONS” ARE PRODUCTED BY MATHEMATICAL MODELS

These are producted by mathematical models, without the operation of the forecaster, and so almost never exhaustive: a variable day can not be summed by “icons”, clear in the morning, clouds in the afternoon and  occational storm on mountain in the evening. Would you let make your medical diagnosis by “icons”? The weather forecast by icons are valid only if interpreted by forecaster  and detailed long daily time. The textual reports are long to read  but they help to delineate a more correct idea of local tones  and they describe also the reason of the expected weather, where the disturbances come from, which is the nature of air masses at stake.

9. THE WEATHER FORECAST SAVE HUMAN LIFES IN CASE OF EXTREME CONDITIONS

The forecast don’t provide just for the day on the beach or the trip on mountain, but they can save human lifes in case of extreme events and they help to make the air, maritime and land transport work, power plant, construction industry, agriculture. This is an invitation not to trivialize them and to have respect of them, like any other product  of human work. And keep in mind, as the british  general Robert Baden-Powell, founder of Scout: “good or worse weather doesn’t exist, just good or worse equippment”

10. THE PRESENCE OF DROPS AND CLOUDS DOESN’T MEAN TO GIVE UP

The presence of drops and clouds in the weather icons doesn’t necessary mean  to give up holidays or trips, sometimes proper clothes or a good plan of itineraries are  sufficient to enjoy open spaces even without clear sky. This is valid for mountain, where the weather can change quickly. During winter is fundamental consult  avalanches and snow reports (www.aineva.it) before a trip on mountain.
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