Phoenix near record for 110 degree days.

[BillyBaroo]

I guess it's been kind of hot up in Phoenix this summer. Tucson has been very nice as we have had a good monsoon this year. I've seen it said that there is about a five degree difference between the two, but after living in both cities, I think Tucson is a lot cooler in the summer. Most of that is because it cools off at night more down here.

New Record Set, 8/29
The Valley of the Sun lived up to its name Wednesday, as locals sweltered through a record-setting 29th day of 110-plus degree heat. Sky Harbor International Airport reported 112 degrees at 3:45 this afternoon.

According to the National Weather Service, highs around 107 degrees are expected through the rest of the week.

azcentral.com members

[Magnum Mike]

Originally Posted by BillyBaroo

I'm very curious to find out if the urban heat island has an effect on thunderstorms in the summer. The heat helps generate the storms, but it seems like extreme heat somehow makes them collapse when they roll into the valley. Anybody notice there's more dust storms and less rain over the last ten years?

I lived in Phoenix from 1985 to 2000, then I moved to Tucson and I've lived here for the last seven years. Right away, I noticed a huge difference in the nighttime temperatures of the two cities. There's a lot more storms in the summer too. This year has been really wet. But I think that has more to do with being further south than anything else. Tucson does have a more natural desert environment though.

The urban heat island does contribute to the diminished amount of rain we've been seeing in the monsoon for the past few years. When a thunderstorm rolls in, areas outside of the Phoenix metro get plenty of rain, but when thunderstorms get over the urban heat island, depending on several factors in the weather system, most of the time they seem to weaken, or in some cases rain falls but it evaporates before it hits the ground. When the pressure from heat island is stronger than the pressure created by the storms, they get pushed away. You can see it sometimes, with blue skies above the valley, but all around it, storm clouds that seem to get pushed away. The only time we'll get rain is if the heat island pressure is weaker than the pressure of the system, and most of the time that happens at night, after the pressure from the heat island weakens, or in the morning before everything heats up. This also explains why we've had most monsoon storms in the middle of the night or early in the morning this year.

Besides the fact that Tucson has a lot of desert areas surrounding it, and I hope it stays that way, the city is also about 1500 feet higher in elevation than Phoenix, so temperatures are naturally cooler by an average of 5 to 8 degrees.

[BillyBaroo]

Just saw this story. Meanwhile, it's raining again in Tucson tonight. I hope you guys can get a little rain tonight too.

Nearly a month of 110 or more in Phoenix
By AMANDA LEE MYERS, Associated Press Writer

PHOENIX - People here expect it to be hot, but they sure wouldn't mind a cool spell. You know, maybe 107 or so.

Phoenix reached a shoe-melting, spirit-crushing milestone Wednesday: 29 days of temperatures 110 degrees or higher in a single year. The previous record of 28 days was set in 1970 and matched in 2002, according to the National Weather Service.

The streak is enough to vaporize any humor left in the phrase "It's a dry heat." The average number of days 110 or higher in a given year is 10.

"It's a dry heat because we're in a desert!" Ollie Lewis said as she walked to a bus stop in downtown Phoenix.

Austin Jamison, a forecaster with the National Weather Service in Phoenix, said an oven produces dry heat, too. "You can put your head in the oven, but that's not comfortable."

The temperature hit 113 degrees Wednesday afternoon, matching the record high for Aug. 29 set in 1948 and 1981, Jamison said. The weather service is forecasting temperatures of 105 degrees for the rest of the week.

The National Weather Service says urbanization and global climate change could be contributing factors to the heat, but Phoenix has not come close this year to its all-time high of 122 degrees, set in 1990. The hottest day of 2007 was July 4, when the mercury hit 116 degrees.

Still, the string of broiling days was tough to deal with, even for lifelong Phoenix residents like Martin Milner, a construction worker who took a break under a rare shade tree.

"People say you'll get used to it, but you never get used to it," said Milner, who wore a bandanna under his black hard hat to stop the sweat from running down his face. "Every year it gets harder and harder and harder. This year it's just skyrocketed."

Marcia Reid, who moved to Phoenix from New York City five months ago, said the heat doesn't bother her.

"I lived in New York for so long, I got tired of the cold," she said. "I like it here.

"It's a dry heat."

[BillyBaroo]

Originally Posted by Magnum Mike

The urban heat island does contribute to the diminished amount of rain we've been seeing in the monsoon for the past few years. When a thunderstorm rolls in, areas outside of the Phoenix metro get plenty of rain, but when thunderstorms get over the urban heat island, depending on several factors in the weather system, most of the time they seem to weaken, or in some cases rain falls but it evaporates before it hits the ground. When the pressure from heat island is stronger than the pressure created by the storms, they get pushed away. You can see it sometimes, with blue skies above the valley, but all around it, storm clouds that seem to get pushed away. The only time we'll get rain is if the heat island pressure is weaker than the pressure of the system, and most of the time that happens at night, after the pressure from the heat island weakens, or in the morning before everything heats up. This also explains why we've had most monsoon storms in the middle of the night or early in the morning this year.

I've noticed that a lot this year. When I look at the weather radar I'll see storms rolling into the valley and then they dry up when they hit the southeast edge around Chandler and Mesa. When you do get storms, you're getting them more at night and in the morning. It's different from when I lived up there and the storms used to come in the late afternoon.

I was up there last Saturday night for the Cardinal game and it was a nice evening. I think there was a lot of cloud cover coming from the remnants of Hurricane Dean.

[BSL63087]

I think there is something to the heat island effect. I have been researching the DFW area and I have seen several people say that the Fort Worth side of the area tends to get the worst part of storms and tornadoes while the eastern side on towards Dallas hasn't had a tornado in 50+ years from what I understand. It may just be coincidence but it makes sense to me.

[BillyBaroo]

Originally Posted by BSL63087

I think there is something to the heat island effect. I have been researching the DFW area and I have seen several people say that the Fort Worth side of the area tends to get the worst part of storms and tornadoes while the eastern side on towards Dallas hasn't had a tornado in 50+ years from what I understand. It may just be coincidence but it makes sense to me.

That's interesting the weather could change because of all the growth in Dallas over the last fifty years. Understanding climate and weather is tricky though because we get statistics from the last 150 years and then try to find patterns for the history of Earth using such a small sample. Just a few years ago a significant study of the monsoon was started and they've published some very interesting reports. It's called the North American Monsoon Experiment (NAME). If you put it in your search engine, a ton of stuff will come up.

Here's a story from last year about what NAME is.

EO News: Experiment on Monsoon Season Rainfall Lives Up to Its 'Name' - May 3, 2006 (http://earthobservatory.nasa.gov/Newsroom/NasaNews/2006/2006050322204.html - broken link)

And this is a link to a report that has a bunch of good information.

http://www.eol.ucar.edu/projects/nam...soon_sep04.doc

[Elmonellie]

Did anyone ever see the Twilight Zone episode with the woman left in NYC when everyone flees to Fla? It was a great show...I think of it a lot now that we are seeing so many over 100 days. Oh, and by the way, I love Phx. Just a thought.

[Bill-]

Here's a bit about a study that seems to suggest that urbanization and heat islands increase rainfall.

There's a change in rain around desert cities

[Ponderosa]

Several years ago I participated in a study attempting to document the urban heat island impact on summer thunderstorms near Phoenix. Study members flew around in heavily instrumented aircraft collecting data when storm conditions were ripe during July and August. I forget the exact outcome, but we clearly were able to observe elevated temps at low elevations above and around the PHX area, but were unable to demonstrate that it had any impact on thunderstorms. I was left with the impression that the heat island, while a factor in human comfort in the inner city areas, is simply too much of a microscale phenomenon to have much material effect on mesoscale thunderstorm complexes.