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> Graupel vs. Sleet, What is Graupel?
jdc123
post Feb 7 2008, 10:00 AM
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Got a precipitation question for all you gurus out there. Could you explain to an amateur what the difference between graupel and sleet is? Earlier this week in NE Pennsylvania we had about 1.5 inches of what I thought was sleet come down. I didn't measure the size of the pellets, but I could scoop it up in my hand like a handful of small chocolate chips. Any idea which it was?


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WeatherMatrix
post Feb 7 2008, 11:25 AM
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QUOTE(jdc123 @ Feb 7 2008, 10:00 AM) *
Got a precipitation question for all you gurus out there. Could you explain to an amateur what the difference between graupel and sleet is? Earlier this week in NE Pennsylvania we had about 1.5 inches of what I thought was sleet come down. I didn't measure the size of the pellets, but I could scoop it up in my hand like a handful of small chocolate chips. Any idea which it was?


Short answer - if it was during a thunderstorm, or the storm was convective in nature without thunder, it was probably hail, especially given the size you have quoted.

My understanding is that Graupel is the same thing as Snow Pellets (WikiPedia backs this up and says that their size is 2-5mm) There are also Snow Grains which WikiPedia says are very small (<1mm) and "don't bounce or breakup on impact" like Snow Pellets. All of those things, like snow and sleet (ice pellets), are produced by winter weather situations.

Hail is produced only by thunderstorms or at least convective clouds (meaning there are vertical circulations where the hail is carried up and falls down, accumulating another layer of ice around a nuclei).

Hail can be any size but, to my knowledge, Sleet is always BB-sized or smaller (WikiPedia says that Sleet is almost always smaller than Hail)

Both Hail and Sleet look like ice - they are not white in color - and I believe that Snow Grains and Snow Pellets (Graupel) are white.

I believe that Hail and sleet routinely accumulate to more than an inch, Snow Grains and Snow Pellets (Graupel) do not.

So, given all this, I would say that, providing it was clear in color, what you saw was probably hail, because it was too big to be sleet. But the only way to be sure would be to know whether or not it came from a convective cloud. In rare situations like we have had recently in the Northeast, it can be tough to tell the difference between sleet and hail, especially when it is small hail and it's convective, but yet cold enough for sleet to fall.

If you give me a specific date and time, I could look up Hail reports in your area, and this would confirm my assumption.


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jdc123
post Feb 7 2008, 05:09 PM
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Thanks for answering! I'm a fairly new member but I've already found that this is a great place to learn!

I believe the storm was on the 1st of February, and it "hailed" for most of the day. I've been wondering about it ever since. There was no thunder, yet I can't say if the storm was convective as you said it might be. Wish I had made observations throughout the day, or had a station that would keep track of the details for me.

Thanks for your time.


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BtownWxWatcher
post Nov 16 2008, 09:09 PM
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What Is Groupel?

Anyone know?


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I-95blizzard
post Nov 17 2008, 02:53 PM
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Sleet


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AnthonyS
post Nov 17 2008, 06:20 PM
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QUOTE(NickBlizzard @ Nov 16 2008, 10:09 PM) *
Anyone know?


Well, this belongs in the "weather question" forum, but I'll still answer it. smile.gif Graupel (AKA snow pellets) has a diameter between 1 and 5 mm. They are crunchy and break apart when squeezed. They usually fall during showers. They form via accretion of supercooled water droplets onto a snowflake.

Anthony


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AnthonyS
post Nov 17 2008, 06:24 PM
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QUOTE(I-95blizzard @ Nov 17 2008, 03:53 PM) *
Sleet


No. Sleet is a frozen raindrop. Graupel is different in that it is a snowflake that accretes layers of super cooled water droplets in a convective cloud, which rimes the snowflake until it is no longer identifiable.

Anthony


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bubbles
post Nov 18 2008, 08:58 AM
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laugh.gif man, we don't get any of that stuff here.
this is the first time I've even heard of grauple...
I think I have seen it hail twice in the 20 years I've lives in Phx. laugh.gif


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AnthonyS
post Nov 18 2008, 09:23 AM
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QUOTE(bubbles @ Nov 18 2008, 09:58 AM) *
laugh.gif man, we don't get any of that stuff here.
this is the first time I've even heard of grauple...
I think I have seen it hail twice in the 20 years I've lives in Phx. laugh.gif


That's the benefit (or downside) of living in a subtropical desert.

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jdc123
post Nov 18 2008, 07:35 PM
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QUOTE(AnthonyS @ Nov 17 2008, 07:24 PM) *
No. Sleet is a frozen raindrop. Graupel is different in that it is a snowflake that accretes layers of super cooled water droplets in a convective cloud, which rimes the snowflake until it is no longer identifiable.

Anthony


Yes, and if the graupel is bigger than 5mm, then it's classified as hail. Just to throw out another form of precipitation, what do you know about snow grains Anthony? I'm thinking that if it's under 1mm, then it's a snow grain (or snow granule wink.gif ), if it's 2-5mm, then it would be graupel. No?


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AnthonyS
post Nov 18 2008, 08:09 PM
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QUOTE(jdc123 @ Nov 18 2008, 08:35 PM) *
Yes, and if the graupel is bigger than 5mm, then it's classified as hail. Just to throw out another form of precipitation, what do you know about snow grains Anthony? I'm thinking that if it's under 1mm, then it's a snow grain (or snow granule wink.gif ), if it's 2-5mm, then it would be graupel. No?


Snow grains are the equivalent of drizzle, except the components are frozen. They can be crystalline, partially melted, resemble tiny, tiny ice balls, etc. You're correct when you say that snow grains have a diameter of less than 1mm, but incorrect when you compare them to graupel and hail. Snow grains develop via diffusional growth or the Bergeron process in stratus clouds. Hail and graupel materialize the same way, except they occur in convective clouds where updrafts needed for layers of ice accretion are present. Also, if the precipitation is between 1 and 5 mm, it can either be snow pellets or ice pellets, depending upon its level of "crunchiness."

Anthony


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jdc123
post Nov 18 2008, 08:13 PM
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QUOTE(AnthonyS @ Nov 18 2008, 09:09 PM) *
Snow grains are the equivalent of drizzle, except the components are frozen. They can be crystalline, partially melted, resemble tiny, tiny ice balls, etc. You're correct when you say that snow grains have a diameter of less than 1mm, but incorrect when you compare them to graupel and hail. Snow grains develop via diffusional growth or the Bergeron process in stratus clouds. Hail and graupel materialize the same way, except they occur in convective clouds where updrafts needed for layers of ice accretion are present. Also, if the precipitation is between 1 and 5 mm, it can either be snow pellets or ice pellets, depending upon its level of "crunchiness."

Anthony


Thanks for pointing that out. Still trying to sort out the "official" titles for these. Maybe I'll just stick to saying it's "precipitating" outside. tongue.gif


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