The rain has moved in for Thursday night into Friday morning. We can’t rule out a bit of thunder early Friday but not expected any severe storms. There could be a few folks with an inch in the rain bucket.
While the heaviest rains should end Friday AM, we could see spotty showers throughout the day.

Saturday may bring a few passing sprinkles as well.

Sunday looks wet!

At 11:37 am, a line of thundershowers was pushing into the northwest corner of Middle Tennessee. Henry and Stewart counties have dealt with heavy rain and gusty wind, as well as isolated pockets of small, non-severe hail. Places like Clarksville and Erin could see wet weather after midday into the early afternoon, including counties like Montgomery, Houston, Humphreys and Benton. Nashville and the rest of the mid-state should stay mainly dry the next couple of hours, although scattered t’showers could develop in our area before the afternoon commute.

I must have told a dozen people over the last month that the way the tropical systems have been getting “sheared” this year (not allowing them to develop fully), makes it seem like an El Nino year.

Well, low and behold, the National Oceanic and Atmospheric Administration has issued and unscheduled El Nino Advisory! They say that over the last two weeks, sea surface temperatures have increased remarkably over the equatorial Pacific Ocean. Jeff mentioned this on his blog and I’ll provide the link to read the whole advisory at the end of this blog entry.

So how sea surface temperatures in the Pacific affect tropical systems in the Atlantic, Caribbean, and Gulf of Mexico? Here’s the answer:

The warmer than normal difference in temperature of the El Nino waters in the equatorial Pacific compared to the cooler water just to the north, help create a “sub-tropical jet stream” during the winter that runs across Mexico and the southern United States into the Atlantic. During the summer, it’s not really a jet stream anymore, but these “westerly” wind currents are much farther south than normal, shearing the tropical systems as they try to form (in the easterlies), keeping many of them from fully developing.

You might say that in the low levels of the tropics an easterly flow prevails, while in the higher levels a westerly flow prevails, hence the shear.

Caution should be taken, though, since we still are in the peak of the hurricane season. It’s not like a major hurricane won’t form at all during an El Nino, but there are ususally fewer of them.

In winter, a strong El Nino causes the southern states to be warmer and wetter than normal. Thad doesn’t mean it won’t get cold at all. It just means that when Dec.-Feb. is averaged out at the end of the winter, the result is warmer and wetter, due to that sub-tropical jet stream.

To read the whole advisory click below:
http://www.noaanews.noaa.gov/stories2006/s2699.htm

Through 1:00 pm the Nashville Airport has received 0.33″ of rain. The rain guage on the roof at News 2 has seen double that with 0.61″. No shortage of clouds for the mid-state, but there are breaks in West Tennessee around the actual cold front. Isolated showers are trying to develop along the front, and if they come together they could reach our area late in the day or tonight. I think the clouds will stay stubborn for most of Middle Tennessee the rest of the afternoon. Temperatures around Memphis have jumped into the middle 80s with the peeks of sunshine. Areas west of I-65 might see some of that sun before 7:00 pm (around sunset). Expect a few passing showers through tonight and tomorrow morning, but it won’t be as steady as what we’ve seen this morning and this afternoon. There could be a few breaks of sun tomorrow behind the front, but most of the day will be cloudy as the low level moisture on the backside of this system hangs tough (an isolated shower isn’t out of the question). That will mean another day with highs in the 70s. The low clouds will clear the area by Thursday afternoon, with warmer weather expected by Friday and through the weekend.

Or is it off the wagon? At any rate, Storm Tracker is back on-line. As I type (10:19 am) the loop up top is in the process of rebuilding. You can click here for the latest Storm Tracker image.

Having a temporary issue with the Storm Tracker radar loop; in the meantime you can rely on the NWS Middle Tennessee radar. Love computers!

Everyone remembers where they were and what they were doing the morning of September 11th, 2001. I was a junior studying meteorology at Penn State. I had a mid-morning weather communications class on Tuesdays and Thursdays so I usually slept in until 8 or 9 o’clock. A friend in the dorm called me in tears after the first plane struck the World Trade Center.
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I was going to post this video after John Dwyer showed it to me, but Nashville Is Talking beat me to the punch. No further comments, as the video speaks for itself.

Speaking of records (see previous post) here’s a good piece of Tennessee weather trivia from the Nashville NWS:

On September 7, 1925…A late-summer heat wave brings the hottest temperature ever recorded in Middle Tennessee as Clarksville observes a reading of 112 degrees. The record high for the entire state of Tennessee is 113 in Perryville set on August 9th, 1940.

I’m surprised that the mid-state’s all time high temperature occured in September, just over two weeks before the start of fall (September 23rd). That’s a little more impressive since meteorologists view summer as June/July/August and consider September 1st the start of fall.

Seven of the last eight days have been at or below average in Nashville. The average high temperature (thirty year mean) takes a decent dip through the month of September, from 85 on the 1st of the month to 77 by September 30th. Late summer heat waves are still possible: on this date in 1925, we passed the 100 degree mark for the second consecutive day…in what turned out to be a four day streak of record-breaking heat. Luckily, there’s none of that in the forseeable future.