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East Coast heat: Capital Weather Gang forecast

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Matt Rogers
Meteorologist, Capital Weather Gang
Tuesday, July 6, 2010; 2:00 PM

"Our brutal broiling heat wave is forecast to continue today and tomorrow as big high pressure delivers a pressure-cooker pattern to the area. Humidity levels will not be severe, but they are slowly increasing each day. If there is any good news to be found, it looks as though that super hot upper level high pressure area could start breaking down sooner than expected, meaning that Thursday and Friday could see about a ten degree pull back on high temperatures along with increased chances for thunderstorms," writes Matt Rogers, meteorologist with the Capital Weather Gang.

Rogers was online Tuesday, July 6, at 2 p.m. ET to discuss the blistering heat blanketing much of the East Coast, including heat advisories, air quality and the latest forecast for the week.

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Matt Rogers: Good afternoon and thanks for joining in.

We've been monitoring our current super hot weather pattern and so far here at midday, the latest weather models still want to give us a break by Thursday and Friday. Now a "break" means temperatures in the lower 90s instead of lower 100s along with thunderstorm chances. But I think we'll be wanting to take that sort of break after today and tomorrow.

Please send me any questions you have.

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Bowie, Md.: As I write this, at National it is 100 at noon, and has gone up 15 degrees in the last three hours. The temp. seems to be exploding today, moving much higher then forecast. It seems that 103 will be reached easily. What is the overall record. Why is this happening today.

Matt Rogers: The record for today is 103F from 1999, but the all-time July and summer record is 106F from 1930, so we probably won't hit that one today.

Why today? Well, we are seeing a combined

Matt Rogers: The record for today is 103F from 1999, but the all-time July and summer record is 106F from 1930, so we probably won't hit that one today.

Why today? Well, we are seeing a combined impact from a strong hot ridging pattern in the upper levels and fairly dry surface soil moisture conditions. That is giving us this dry heat situation. Like a desert atmosphere, drier weather can heat up faster and stronger than air with more humidity.

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Washington, D.C.: How dangerous is the high heat for children? Is it safe for my two-year-old toddler's day care to do activities (such as soccer) outside as long as there is plenty of water to drink? Or is this heat and humidity so severe that it is best to stay indoors?

Matt Rogers: Hi, yes, high heat like this can definitely be dangerous for children and the elderly, particularly if strenuous activities are involved. I would definitely consider limiting or postponing the daytime playtime and keeping out of the hot July sun. And you're right, no matter what, stay hydrated.

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Matt Rogers: New 2pm observations: 104F(!) at BWI, 96F at Dulles, and back to 100F again at Washington Reagan National.

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Baltimore, Md.: I was surprised while watching Early Today to see that we are about 10 degrees hotter today than Atlanta. Also, while the heat is baking, the humidity is staying fairly low. This is a weird weather pattern, so I was wondering what accounts for it. Thanks.

Matt Rogers: Yes, we are fortunate that the humidity has stayed lower for the time being. Unfortunately it will be inching up in the coming days.

The current jet stream pattern is such that it is pushing the stronger heat (compared to normal) north and east into the eastern Midwest and East Coast. This big hot "ridge" of high pressure has lots of sinking air, which warms and dries the atmosphere. Down in Atlanta, they are away from this big high pressure and are seeing more clouds and cooling as a result. Right now, Atlanta is mostly cloudy and ONLY 86 degrees!

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Washington, D.C.: Is this extreme heat a result of Global Warming?

Matt Rogers: The record highest temperature for July in DC was 106F set in 1930. The record highest temperature for August was 106F set in 1918. The theory on global warming is that heat waves should become more frequent (see Andrew Freedman's post today on our blog), but as a meteorologist, I know that we see more heat waves on the East Coast when a La Nina is developing in the Pacific as it is doing this particular year.

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Dumfries, Va. -- a/k/a The Surface of the Sun: So that Charlie Sheen movie where there aliens were burning gas in the jungle to raise golbal temperatures was true, eh? I've lived in D.C. my whole 50 years and this is by far the most messed up weather year I can recall. Tons of snow, then blazing hot with no rain. What's next? Locust and plague?

Matt Rogers: Yes, this has been quite a year. One of the major drivers of our big seasonal patterns is right in the middle of the Tropical Pacific. The warm waters that were there this past winter gave us the very snowy situation. And now the waters have cooled dramatically (about .6C below normal as of last week) and that gives us hotter summers here in the East. Hence, the weather yo-yo.

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Arlington, Va. : Love your blog. What does the long range forecast look like for the upcoming fall into winter?

washingtonpost.com: Capital Weather Gang

Matt Rogers: Great question. Right now, it looks like September and October should continue in this warm pattern. Although a more active hurricane season this year could bring us more tropical moisture at times (we'll need it by that point).

The winter is looking quite different than last year with maybe above normal temperatures and below normal precipitation. This winter is looking like it could shape it closer to the 2007-08 winter. We saw some volatility in temperatures, but ultimately it was warmer and (much) less snowy than last year.

Of course, long term outlooks have very low confidence and skill, so we'll have to watch it closely.

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Heat Islands: How much of a difference does the lack of vegitation make on temps? Why don't our idiot planners get the idea to leave trees in place when the build stuff? Just look at the hot lane (no pun intended) project on the Beltway near Tysons. They clear cut every tree for miles and its roasting...we just seem to be dead set on killing this planet.

Matt Rogers: In the early history of city, this area was much more clear-cut than it is now actually. I think the real culprit there is the concrete jungle that is our urban landscape. We've noticed that the biggest impact from heat islands appears to be on low temperatures when the ground can radiate heat out and away overnight, but the concrete tends to retain it longer and stronger. You'll typically see the biggest urban to rural temperature gradients on those overnight low temperatures.

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Washington, D.C.: My dog Skip is really short. If it is 104 outside, will it be hotter close to the ground? Will he melt if I talk him out for a walk?

Matt Rogers: Wow, my Jack Russell is also named Skip! The biggest problem for the poor four-legged folk seems to be the really hot pavement in the late afternoon. It can really retain this heat, so keep your Skip on the grass if you can!

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Washington, D.C.: Love CWG :) Are there any increased chances of a hurricane hitting the DC area with all this extreme weather?

Matt Rogers: Oh wow, you are indeed a glutton for punishment. Record snow, record heat, and a hurricane all in one year? That reminds me of 2003 when we had that big Feb blizzard, record summer rainfall, and then Isabel I believe in September.

The expected enhanced activity in the Atlantic Tropics does increase our risk this year to a higher-than-normal level, but climatology argues that is extremely difficult to get a DC-area hit. My guess is that there may be some coastal close-calls and we may see some tropical leftovers with any Southeast landfalls especially in September or into October.

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Arlington, Va.: I know we have had several hot days this year, but I haven't heard about that many air quality alerts which typically come with the high heat. Have I been missing the alerts or have there been fewer this year?

Matt Rogers: You are correct. There have been fewer. This is mainly due to the drier status of the heat so far this year. When you have more humidity in the air, pollutants are more easily trapped. Also, we've been lucky enough to keep a breeze going during this heat. Stalled air stagnates. Now I do worry that we'll see higher humidity and stagnant air in August though...

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Washington, D.C.: Someone asked if today's heat is because of global warming and you pointed out that the all-time record high for D.C. was set in July 1930. You know, if the 1930s came back now, there wouldn't be room on the newspapers' front pages for the global warming headlines. (Of course, there were some pretty cold winters in there, too.) I'm no GW skeptic but we do need to keep climate variability in perspective.

Thanks for what you all do.

Matt Rogers: Thanks. That was what I was getting at. And even Andrew points out today in his blog that he can't blame this heat wave on that. We've seen very extreme temperatures and drought before, certainly.

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Rainfall -- or lack thereof: How far below average are we this year? June seemed really dry, but did that erase the gains from all the snows?

Matt Rogers: Great question. Washington National is running just over 6" drier than normal right now since January 1st. So unfortunately we have erased all the snow gains and could really use a good soaker around here. The pattern should get a little wetter later this week and weekend. But more hot spells this summer will continue to challenge our water tables.

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Sun Going SuperNova?: Isn't this all really the result of the sun about to explode? Stars grow in diameter right before going supernova so that would explain why its so hot. What should we do?

Matt Rogers: Haha, well...not too long ago, the Washington Post had a great story on the opposite problem...a sun that has been too quiet lately:

http://www.washingtonpost.com/wp-dyn/content/article/2010/06/21/AR2010062104114.html

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Washington, D.C.: Snow prediction?

Matt Rogers: I'd have to say below normal at this point. The big thing to watch this autumn is the La Nina. If we see it fade/weaken toward a "weak" status, then we could have a shot at a higher season (like 1995-96). But right now, it looks like a moderate to strong event with a drier winter for us.

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Washington, D.C.: I lived in Champaign-Urbana, Ill., as an underpaid graduate teaching assistant for six years. For all six years, I lived in houses and apartments without air conditioning. For those of you who have never been to the Great Plains in summer, the type of weather we're getting right now in Washington, D.C. is ROUTINE summer weather. We could go for six weeks or more with temperatures hitting over 100 degrees and staying over 80 at night. And yes, the humidity is the same in Illinois as it is here. Nonetheless, we still attended sporting events, went jogging, worked outside, etc., etc., without considerably less self-pity than most Washingtonians (although, granted, nobody in Champaign-Urbana had to ride the Metro). It's possible to live like this quite nicely, folks, and many, many people do.

Matt Rogers: Thanks for the pep talk (right?). Did you attend school there in the 1930s? There has been nothing comparable there to six-week strings of 100+ temperatures in recent decades.

I do believe the East Coast typically sees higher humidity levels in the summer compared to central Illinois due to the effects of the Bermuda High.

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El Nino or La Nina?: So this past winter and the current hot spell are related to the pacific ocean temps right? What exactly is the difference between each one and what do you think all this means for next winter? My neighbors were all useless and wouldn't shovel their sidewalks so we were forced to walk in the streets on the way to/from school. Should I invest in a snow blower?

Matt Rogers: Yes, the warm waters from last winter were the El Niņo. It was actually a unique El Niņo known as the Modoki version. That meant that the warmest water temperatures were near the International Dateline. Like 02-03, that gives us more snow due to the warm water's impact on the Pacific jet stream pattern.

The transition in the spring and summer to cooler waters (La Niņa) inversely is tied to finding us with hotter Central to Eastern U.S. summer patterns.

And as long as this La Niņa keeps strengthening, I wouldn't worry about the snow blower just yet.

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Matt Rogers: The 2pm observation of 104F at BWI easily blew past the 101F record from 1999. Otherwise, we have not yet broken/matched records at National and Dulles.

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The Desert, Alexandria, Va.: I can live with the heat, really, but it has been 5 weeks since we had rain at my house in Alexandria, except that one storm last Monday, I think, which was brief and the rain just ran off the dry soil. This is horrible. My garden is dying, despite watering, because the plants are not the type one gets for a garden in Arizona. We really need a week of solid, steady rain. A few thunderstorms are not going to do it. I can only imagine what farmers are going through.

Matt Rogers: You are correct and from what I can see, I do not yet see any of those long-term rain prospects. Saturday is looking wetter on the midday models with frequent showers and storms possible, but we wouldn't be able to offset this deficit with that.

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Water Shortage - Hurricane?: So if we're way below normal for the year and no real changes in the pattern, what gets us back on track? A tropical storm or hurricane that comes up the middle or the bay?

Matt Rogers: Yes, that has been good for us in other dry years. Even if we get the remnants of one.

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Matt Rogers: Well, the 3pm observations are in and DC is at 101F, Dulles is at 99F, and BWI is hanging strong at 104F!

Look for this heat to continue tomorrow with maybe slightly more humidity (sorry), but we should start tearing this down by Thu and Fri along with more thunderstorm chances.

So hang in there, stay cool, and thanks for joining the chat today!

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