Sunday, January 05, 2014

The Anatomy Of an ARCTIC BLAST: 2014 vs Previous -15 Days

We don't reach -15 or below very often in northern Ohio--only 12 times in 140+ years of record keeping. Signs of arctic cold show themselves in the temperatures above the earth's surface away from surface influences such as concrete.

To be clear, not every instance of below zero nights or days is exactly alike. Several parameters need to be in place for this to occur in northern Ohio: COLD AIR ALOFT (850 mB level - 5000 ft), clear skies and snow cover.  How cold do the 850 mB temperatures have to get to reach, say -15 or lower?  Looking back at the 6 coldest readings in Cleveland history (I also threw in 2009 because that was the last time we fell to -10 or below), the west to east 850 mB temperature profile looked different each time

The 1/19/1994 record low event looked like this at 850 mB. Cold core was north of the Great Lakes.
850 mB temps fell to between -30 to -32
1/23 and 1/24/1963 was a two day event, -17 and -19 respectively. The 850 mB temp profile was this. NCAR reanalysis was used because the grADS site only goes back to 1979. The temperatures are in Kelvin. Cold core north of the Great Lakes.
850 mB temps fell to around -28 converted from Kelvin
1/20 and 1/21/1985 was another two day event, -18 and -17. Notice how the core of the 850 mB cold was centered in the midwest over Iowa, Illinois and northern Missouri before it moved east into Ohio. The 850 temps were some of the coldest on record. Here is the 24 hour breakdown from the grADS site:

850 mB temps fell well below -30
1/21/1984 was similar in surface temperature yet the 850 mB temps never fell below -25. Once again, cold core north of the Great Lakes.

Based on my checking, the coldest 850 mB temperatures EVER were during the 1/16,17/1982 event with a -38!

Yet the surface temperatures never fell below -13 and -17 over the two days.

850 mB temperature fell to a mind blowing -38 Celsius!
The 1977 two day cold blast...temperatures are in Kelvin. -28 was the coldest in northern Ohio.

Finally, 1/16/2009...850 mB fell to at least -23. Cold core was shallow.
 How about the cold on Tuesday? The 850 mB forecast temperature drops to -30. 

Each instance has a different west to east 850 mB profile with different resulting surface temperatures even though   the 850 mB temps might have been similar to past events.

In other words, the 850 mB temps are only part of the story when it comes to predicting arctic cold overnight lows.

Some cold tidbits for Cleveland:

The last time we fell below zero was in 2011
The last time we fell below -10 was in 2009 when we hit -13 (5 nights below zero)
High temperature at or below zero:  14 Times
The last time was 1994:  -3
The coldest high temperature EVER in CLE:   -5 in 1985
Below zero high temperature happened twice in 1982
Below zero high temperature happened 5 Times in 1899
Winter 1976-77 had 28 instances or below zero temperatures (days and nights)

1 comment:

Dennis Boylan said...

You talk about temps at the 850mb level. How does the lake factor into the temps? Does it being frozen or open have an impact on where the temp can go?