Saturday, July 18, 2009

A cool July weekend... and a commentary on climate record-keeping

UPDATED:
The italicized portion of the post below was written in error and is inaccurate. That portion of the blog is retracted. The rest of the blog stands.

Original Post:
Wow, what a "bonus weekend" we are in the midst of here in the Mid-South! A strong cold front passed through the region and settled down to the Gulf Coast yesterday and on its heels Canadian high pressure has settled in. This has brought us some nice relief from typical July weather which would have us seeing lower 90s for highs and above 70 for lows with a fair amount of humidity.

This morning's low at Memphis International was 64 degrees, which was 2 degrees off the record of 62. Here in Bartlett, WXLIVE! bottomed out at 59 degrees this morning. I'm forecasting similar conditions for tonight, perhaps a degree or two cooler - 63 in Memphis (which would be one degree shy of the record) and 57-58 in the suburbs. Should be a very nice way to wake up Sunday morning! One record that still may go down is the coolest maximum temperature for today at Memphis. The previous record was 82 set way back in 1934 - so far the airport has topped out at 81. We should at least tie, if not break, that 75-year-old record!

Speaking of daily weather records, I learned this week of an oddity in the way climate records are kept during Daylight Savings Time. According to a National Weather Service directive (10-1004, dated September 4, 2008), daily climate records (temperature, precipitation, etc.), as recorded in the CF6 climate record, are computed based on the "Standard Time" clock. So, during DST, the "day" for climate record keeping purposes runs from 1:00am to 1:00am, not midnight to midnight. This directive caused an interesting side-effect on June 28, 2009. The daily low (midnight to midnight) for the day was 81 degrees, which would have set a new maximum low temperature for the day. However, between 12:00-1:00am on the 29th, the temperature dropped to 78, thus the old record of 80 was NOT broken. Personally, I think this is stupid (there, I said it). A DAILY record should not include a part of another day. If you want to look at the directive for yourself, click here and look on page 17, section 4.3.3b. The old record stands; I'm still miffed.

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3 comments:

Cookeville Weather Guy said...

Hey Bro~
We only made it to 73° today and our record low maximum for July 18th is 78°...by the way, you all should count yours as a record, too!

WILLIAM BRANTLEY said...

I totally agree with you Erik.
However You and me do not control the rules with the N.W.S. I wish we could. Maybe someday they will change it. Recently they did change their Tornado Wind Chart. An F5 Tornado now startes at 200 m.p.h.+
If this chart had been good a few years ago I do not remember the exact year right now. The Tornado that hit south Jackson would have been rated an F5 now. Not an F4 back then.

MWN/Erik said...

Thanks for the comments Michael and William! Obviously, I agree with you both.

Michael, we set a daily minimum high yesterday as well - 81. Not quite going to make it today (+2 on record low and over the min high by +2 right now too). Doesn't mean I won't take the weather though!

William, you're right on the Enhanced Fujita scale. That went into effect in 2007.