Last week, for several days I had been noticing that Fort Payne had been having hotter daytime temperatures than I would expect. For example, Fort Payne might have a temperature of 98 degrees and Tuscaloosa might only be at 94. That seemed a bit odd to me since Tuscaloosa is a good bit further south than Gadsden. Additionally I noticed that Fort Payne was several degrees warmer than a weather station on Sand Mountain several miles to the west. That made sense since the weather station at the airfield in Fort Payne is in the Big Wills valley and the other station was several hundred feet higher in elevation on top of Sand Mountain.

After wondering for a while why Fort Payne would be hotter than Tuscaloosa several days consecutively, I consulted Jason Simpson. It didn't take long for us to come up with a theory. It could be possible that the reason why Fort Payne was several degrees hotter than Tuscaloosa is because Fort Payne was under the influence of adiabatic heating because of its location in a valley, and Tuscaloosa was not. Now, this is just a theory, and other factors could have been involved, but this particular factor definitely could have contributed to the situation.

So how exactly could adiabatic heating effect this situation? Well, to begin with, adiabatic processes occur without a heat transfer between a system (such as a parcel of air) and its surrounding environment. The parcel of air can warm and cool adiabatically by changing the atmospheric pressure on the parcel. This is done by changing the altitude of the parcel. When a parcel of air rises, the pressure decreases, and the air expands and cools. When a parcel descends, the pressure increases, the air is compressed, and the parcel heats up. Both of these processes are common near mountain slopes.

So, it could be possible that the weather station at Isbell Field in Fort Payne recorded a higher temperature than the station in Tuscaloosa, because air moving down from Sand Mountain into the valley was compressed enough to raise the temperature by a few degrees. Unsaturated air has a lapse rate of about 5.5 degrees per 1000 feet, which means that a parcel that descends 1000 feet will have a 5.5 degree rise in temperature. So, it is probable that Fort Payne, at several hundred feet lower elevation than the station on Sand Mountain, definitely experienced higher temperatures because of adiabatically heated air. Tuscaloosa, on the other hand, has no change in elevation of that magnitude anywhere close, so adiabatic heating induced by topography would not be a factor.

So, that may be the reason why Fort Payne was a little bit hotter than Tuscaloosa for several days last week.

Drew McCombs
ABC 33/40 Weather Intern
abc3340wx2@gmail.com

Scattered showers persist over Extreme SE Alabama this evening and there was a cluster of strong thunderstorms from near Tuskegee over to near Auburn and Opelika.

Moving toward the ENE

The rest of the state (the vast majority) was free of showers at 8'oclock this evening.

The 33/40 Skywatcher for Childersburg reported 2.46 inches of rain this afternoon bringing the three-day total to almost four inches (3.96)

Anniston Airport reports 1.43 inches of rain today.

The hottest temperatures were over on the west side of the state. The high was 93 in Tuscaloosa and 95 in Muscle Shoals.

Almost the entire NW half of Alabama no showers late this afternoon.
At 5:50 pm, the strongest storms were over Tallapoosa, Elmore and North Autauga County. Movement generally NE.

Scattered showers and thunderstorms were more numerous over the Extreme South

MT CHEAHA
Only 73 degrees atop the mountain just before 6 pm and they got 1.32 inches of rain this afternoon.

(NOTES FROM TROUBLE SPOTS)

NEW YORK CITY
Major power outages persist, but it was a pleasant 79 degrees late this afternoon.

ST LOUIS
Thousands still without power mainly from a huge storm at the middle of last week. Heated up a bit today after a comfortable weekend. The 5 pm temperature was 89 but the dew point only 56...so the humidity is still low.

PHOENIX
Low this morning of 95 was within one degrees of the hottest overnight low ever. Sunday's high of 114 was a record for the date. These temperatures late this afternoon:

112 in Phoenix
115 at Gila Bend, Ariz. (pronounced Hela Bend)
118 at Needles, Calif.

We absolutely could not do without computers in the world of weather. But, sometimes they throw us a curve.

Blog reader, Dana, reported that an automated computerrised weather station on the north part of Hilton Head Island, S.C., reported a low and high today of 150 degrees. The heat index was 195.

Around mid-day, the automated weather equipment at Gadsden Airport reported a wind gust of 92 mph. It was a faulty report.

The strongest thunderstorms were over two areas:

* Extreme SE Talladega and SW Clay County in East Central Alabama. These will be moving eastward across Clay county toward Millersvill, Mellow Valley and Ashland. Lots of lightning and brief heavy rain.

* Over a good part of Chambers County. Slso moving east to NE.

Scattered thunderstorms a little more numerous over the southern 1/4 of state.

Earlier, a road was blocked by fallen trees or tree limbs in Wilsonville in Extreme Eash Shelby County.

MT CHEAHA
The 3340 Skycam site on Cheaha has already recorded 1.32 inches of rain so far today.

A severe thunderstorm has developed in extreme East Shelby County.

The NWS has issued a Severe Thunderstorm Warning for East-Central Shelby County and SW Talladega County. This includes Sylacauga and Childersburg as well as Wilsonville. The storm was located near Wilsonville or about 8 miles SW of Childersburg and moving east at 10.

May produce nickel-size hail and gusts over 60 mph and, of course, very dangerous lightning.

Otherwise, the more numerous showers and storms were over the southern 1/4 of the state.

All moving from SW to NE

LATE REPORT
At 3:43 pm, public reported tree limbs blocking road in Wilsonville.

***There will be no afternoon map discussion video today... in the process of making the major migration to the Mac OS X platform. I will have one ready bright and early tomorrow morning. This morning's video is still very valid:

http://www.jamesspann.com/

WOW: Our brand new SKYCAM is up and running at Gulf Shores. The view is stunning... and you can see it online here:

http://www.abc3340.com/static/skycams/skycamsgulfshores.html

Tropical squalls have been moving through the coastal waters this afternoon, and as you can see our site has recorded a peak wind gust to 51 mph. The rain total as I write this is 0.35" and rain is falling heavily. The SKYCAM site is at the Phoenix AllSuites, just east of the Gulf Shores pubic beach. Thanks to our friends at Brett-Robinson for making this happen; this will be quite a service to all Alabamians. And, of course, our partner in the entire project is Compass Bank. We thank them for their partnership. More SKYCAMs will be coming on line in the next two weeks.

TROPICAL TROUBLE: Sure looks like a new tropical depression is forming over the southwest Gulf of Mexico. Take a peek:

http://www.ssd.noaa.gov/goes/flt/t1/avn-l.jpg

Here is model output:

http://www.sfwmd.gov/org/omd/ops/weather/plots/storm_98.gif

Sure looks like a drought-buster for the Rio Grande Valley... and much of the Texas coastal plain. I will have to hit the rain harder for our affiliate radio stations in Texas... in McAllen and Eagle Pass.

THE ALABAMA STORY: Quite an impressive surge of moisture up through South Alabama into the eastern side of the state. A whopper of a storm is moving through Talladega County. We are watching it from the Mt. Cheaha SKYCAM... at Cheaha they have already picked up 1.31" of rain today from an earlier storm... this one has the potential to push their total to over two inches. Sure nice to see these big rain amounts... over three inches in Birmingham over the weekend and over two inches at Lake Purdy.

In coming days, the old front over the central part of Alabama will fizzle out, and an upper air high will slowly build overheaad. So, we will maintain a typical summertime forecast for this week and the coming weekend. Temperatures should be near normal for late July, with daily highs around 90 or slightly higher. Each day we will be dodging afternoon showers and storms, but they will be scattered. And, the determining factors for the coverage of the storms on daily basis is found only in the mesoscale, and is very hard to identify days in advance.

Sure enjoyed seeing the kids at the New Life Church summer program down in Tuscaloosa this morning... look for them on the KIDCAM today at 5:00 on ABC 33/40 News.

Again, we should be complete with the computer work and have the video back to the "two a day" schedule tomorrow.... J.B. will keep you updated on short term weather for the rest of this afternoon and this evening.

Small but noisy thunderstorm forming over Extreme east Jefferson County between trussville and Leeds.

Otherwise over in East Alabama the strongest storms were over Randolph County.

Everything moving east and NE.

Here is today's update from the Birmingham Water Works...

(we should note Lake Purdy received over two inches of rain this weekend, and water levels are rising)

DROUGHT WATCH!

For Sunday, July 23, 2006

Latest 24 hour Water System Delivery 110,081

Lake Purdy Capacity 75.18%

TODAY’S WATERING GUIDELINES

Monday July 24, 2006

Even-numbered addresses means the house address, box number or rural route ends with the numbers 0, 2, 4, 6, 8 or the letters A-M, or at locations with no address at the even-numbered side of the street. Post Office Box numbers are not included.

CONSERVATION TIP OF THE DAY:

Don’t allow sprinklers to water your street, driveway or sidewalk. Position them so water lands on the lawn and shrubs and not the paved areas.

Not much of Alabama getting rain at this hour, but a cluster of showers and probably some thunderstorms developed rather quickly over the east central part of the state. Just before 11:00 a.m., the heaviest showers were over NE Talladega County approaching the Anniston-Oxford area and mostly east of Lincoln. Other lighter showers extend up into Cherokee County. Still others were forming to the south in Coosa, Tallapoosa and Chambers Counties. They were all moving toward the NE.