Icestorms: Carolina stats 1950-99 & Carolina-ATL compari

[LarryWx]

The Carolina portion of this analysis is based strictly on the document that can be found at the following URL that was posted by Mr. Bob at WWBB:

http://www.americanlifelinesalliance.or ... maries.pdf

- For the 50 years 1950-99, there were 32 Carolina ice storms or an average of 0.64 per winter.

- 23 of the 50 winters (46%) had one or more ice storms.

- 5 of the 50 winters (10%) had exactly two ('63-'64, '71-'72, '81-'82, '89-'90, '95-'96).

- 2 of the 50 winters (4%) had exactly three ('59-'60, '78-'79).

- Largest # of winters in a row without one: 4 ('55-'56 through '58-'59).

- Using my own criteria for Atlanta, which I believe to be pretty similar to this Carolina document, as well as my own Atlanta ice storm records, there were about ten times as many ice storms that affected some portion of the Carolinas vs. at least a significant portion of the Atlanta area (32 vs. only 3) for the period 1950-1999. Two of the three Atlanta storms were also listed as Carolina ones.

- However, Atlanta interestingly enough had TEN ice storms for the period 1900-49 (about 1 every 5 years) based on my own research vs. the THREE for 1950-99 (only about 1 every 17 years)! So, it appears that Atlanta may have been in an ice storm drought for some reason during 1950-99. I would have liked to have been able to see the 1900-49 Carolina stats to compare to Atlanta. Another interesting observation: the new 50 year period of 2000-49 already has seen TWO Atlanta ice storms! (both during 1/00)

- Per the Carolina document for what it is worth for GA statistics, I counted 11 Georgia ice events for the period 1950-99 if I add the 3/2-3/3/1960 storm to the GA list being that it produced QPF of 1" in the Atlanta and other areas of north GA. We already know there were more than 11 since the historical 1/73 Atlanta ice storm was excluded (I assume because it didn't have a great Carolina impact). So, there were at the very least 12. I counted at least 7 of these 12 that appeared to have had their greatest GA impact in either or both of NE and east central GA.

1950-99 Carolina ice storm breakdown by dates:

11/16-11/30: 1
12/1-12/15: 3
12/16-12/31: 5
1/1-1/15: 6
1/16-1/31: 4
2/1-2/14: 5.5
2/15-2/29: 4.5
3/1-3/15: 2
3/16-3/31: 1

If a storm straddled two date categories, I counted it as one half for both cat.'s.

Larry

[Stormsfury]

Larry, as always, great research and thanks for that information ...

SF

[QCWx]

Great job on the research Larry.

[HeartofNC]

So Larry,

With those stats, does it look like the Carolina's will be seeing an ice storm or two this year?

[LarryWx]

SF/QC, thanks/you're welcome.

[LarryWx]

So Larry,

With those stats, does it look like the Carolina's will be seeing an ice storm or two this year?

HeartofNC,
Of course, these stats don't tell me whether the Carolinas have a better or worse than average chance for one or more ice storms. They just tell me what that average chance actually is based on 50 years of data, a nice amount of data. As far as this year's chances, that is up to each individual seasonal forecaster to determine. Statistically/climatologically, it is pretty close to a toss-up.

Now looking at the averages, the stats tell me these things:

1) About 1 of every 2 winters sees an ice storm that meets the specified criteria at least somewhere in the Carolinas based on the stat that says that 23 of 50 winters (46%) had one or more. Note that the stat refers to SOMEWHERE in the Carolinas NOT EVERYWHERE. Unlike Atlanta, I didn't present any stats for any one city. That is one reason Atlanta's stats are so much lower than the Carolinas a a whole. I'm comparing the geographical area of one city with that for two states. Obviously this factor alone has to skew the results of the comparison. I probably should have mentioned this in the original post.

2) IF this winter does have at least one, there is about a 1 in 3 chance that it will have a total of either two or three per the stats.

3) During any one winter, here are the chances for AT LEAST one Carolina icestorm having occurred by a certain date based on the 1950-99 stats:

11/30: 2%
12/15: 6%
12/31: 16%
1/15: 26%
1/31: 30%
2/14: 37%
2/29: 44%
3/15: 46%
3/31: 46%

So, the bulk of them occur from 12/16 through 2/29. Actually, 84% of the 32 ice storms of 1950-1999 occurred during the interval 12/16-2/29. So, we'll still be VERY early in the ice storm season even a week from now.