Weather Wednesday

Those of you who know me well, know that when I was a young whipper-snapper, I originally went to college to study Meteorology.  Upon arriving at University, I discovered that the Atmospheric Science Department wanted me to take Calculus.   Thus ended my dream in a fiery blaze.

Of course I took as many weather courses as my general education credits would allow, one of my favorites was weather forecast models and analysis.  It was during that course that I learned how to do basic forecasting using computer model data.  But that isn’t the purpose of this post.

Weather Wednesday I’m hoping will be an opportunity for people to ask questions about the weather and get some sort of simple answer back.  The questions can be about anything from why does it rain to what was the jet structure of the March 1993 super-storm.  If you have a question send it to wr7681@albany.edu

To get us started this week, we will look at the difference between Hail and Sleet.

There are actually several forms of Ice which fall from the sky.  One everyone is at least aware of is Snow, but there is also, Sleet and Hail.

Hail is formed when water droplets are forced upward by violent updrafts in Thunderstorms.  These droplets are lifted above the freezing level, where they cool and crash into and join other water droplets.  Eventually these combined droplets become too heavy for the updraft to keep suspended and they fall towards earth.  The vast majority of hail, melts long before reaching the ground.  However, in the most violent of storms water droplets are forced to near the top of the troposphere if not a bit beyond and can grow quite large, up to the size of a grapefruit or softball.  No doubt some melting occurs on the way down, so these hail stones might have been even bigger in the storm!  Hail can only form in Thunderstorms.  Hail is typically found in warmer months (Which vary where you live), but can occur at anytime during the year in a Thunderstorm.

Sleet can be formed in two ways, one when snow falls it falls through a warm layer above the surface, melting the snow flake into a rain drop.  This rain drop then falls through a deep layer of below freezing temperatures and re-freeze but don’t have enough time to become snow.  Thus in winter storms you may hear the ping-ping-ping of sleet against your window.  Unlike hail, which is comprised of multiple droplets stuck together, sleet is simply a frozen rain drop.  It is clear and looks like a small pebble.  The second way sleet forms is very similar to the first, when there is lots of warm air aloft and rain then falls into a deep layer of below freezing temperatures and arrives at the surface.  Sleet can only  form from stratiform precipitation and also only occurs in colder months (wich vary depending on where you live).

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2 responses to “Weather Wednesday

  1. The vast majority of Hail melts before ever reaching the ground, a thunderstorm has to get going pretty good to even get pea sized hail to the surface. What is really amazing is when you get those reports of golf ball or larger sized hail. Since they no doubt experienced some melting on the way down, they must have even been larger when in the upper part of the storm!

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