Precipitation type - newly added
We have just launched the "Precipitation type" overlay, displaying these types of precipitation:
Rain, Freezing rain, Mixed ice, Snow, Wet snow, Rain with snow, Ice pellets.
What does Ice pellets mean? Is it hail?
My guess is having lived in a northern part of the US in the past, we called it sleet. The difference is raindrops fall but freeze before hitting the ground. Hail bounces around up in the air adding layer and layers. Sleet is a cold weather issue and hail is a warm weather issue.
Smaller than hailstones. Less than 5 mm in diameter.
Also, sleet tends to be softer pellets where hail is frozen rock hard.
Ahh.. Ok, now I know.. in German. we say Graupel
Hi @Tomber42 , it's different. We don't actually have a "hail" icon nor a layer for it. Hail normally occurs in rainstorm or thunderstorm, and is the result of strong updrafts that repeatedly carry growing chunks of ice upwards into the clouds. Unlike freezing rain, graupel or ice pellets (that are softer and smaller in size), hail is hard as stones, bigger in size and causes extreme damage (dents in metal etc)... In general, hail is difficult to predict as there are quite a few ingoing influences and complicating factors that interfere with the course of the storm.
As @JimInSanDiego correctly summed it up: Hail is a warm weather issue, while freezing rain or ice pellets (sleet) are manifestations of cold weather.
Here is a quick tutorial to describe the differences between: hail, graupel (soft hail / snow pellets), ice pellets (sleet) and freezing rain. Wikipedia puts it this way:
HAIL is a form of solid precipitation. It is distinct from ice pellets (American sleet), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. [...] Unlike other forms of water ice such as graupel, which is made of rime, and ice pellets, which are smaller and translucent, hailstones usually measure between 5 millimetres (0.2 in) and 15 centimetres (6 in) in diameter.
In more detail: https://en.wikipedia.org/wiki/Hail
GRAUPEL (from German language), also called SOFT HAIL or SNOW PELLETS, is precipitation that forms when supercooled water droplets are collected and freeze on falling snowflakes, forming 2–5 mm (0.08–0.20 in) balls of rime. Graupel is distinct from hail, small hail and ice pellets: the World Meteorological Organization defines small hail as snow pellets encapsulated by ice, a precipitation halfway between graupel and hail.
In more detail: https://en.wikipedia.org/wiki/Graupel
ICE PELLETS (American: SLEET) are rain drops that have frozen before they hit the ground. When they hit the ground, they bounce. Ice pellets are also called sleet and can be accompanied by freezing rain. In winter, precipitation usually begins falling out of a cloud as ice particles.
In more detail: https://en.wikipedia.org/wiki/Ice_pellets
FREEZING RAIN is the name given to rain precipitation that freezes on contact on surfaces maintained at temperature below freezing by the ambient air mass. Unlike sleet, a mixture of rain and snow, ice pellets, or hail, freezing rain is made entirely of liquid droplets. The raindrops become supercooled while passing through a sub-freezing layer of air hundreds of meters above the ground, and then freeze upon impact with any surface they encounter...
In more detail: https://en.wikipedia.org/wiki/Freezing_rain
Marienka last edited by
Here I found some interesting link with illustrative pictures:
Will it [freezing] RAIN, SLEET or SNOW?
And what is wet snow? What's the difference between wet snow and rain with snow?
eshtewi last edited by
Dear All, Dear @Marienka
may I ask the algorithm behind this new overlay? I'd like to use the same algorithm to calculate the type of precipitation in my country. I'm running WRF model for my research activities at the Iskenderun Technical University. Thank you very much for your response in advance.
Happy new year to all.