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U.S. heat wave blamed for 22 deaths; Bret and Cindy no threat

By: Dr. Jeff Masters , 3:07 PM GMT on July 21, 2011

The dangerous U.S. heat wave of July 2011 will continue to bring another day of exceptionally humid heat to over 100 million Americans today, with 33 states plus the District of Columbia currently under heat advisories. The heat index--how hot the air feels when factoring in both the temperature and the humidity--exceeded 100° in twenty states in the Central and Eastern U.S. on Wednesday, peaking at 123° in Council Bluffs, Iowa. At least 22 deaths are being blamed on the heat in the Midwest. The extreme humidity that has accompanied this heat has made it a very dangerous one, since the body is much less able to cool itself when the humidity is high. The high humidities are due, in great part, to the record rains and flooding in the Midwest over the past few months that have saturated soils and left farmlands flooded. Accompanying the heat has been high levels of air pollution, which also contributes to mortality. Air pollution is expected exceed federal standards and reach code orange, "Unhealthy for Sensitive Groups", in at least 22 states today, according to the latest forecasts from EPA.

The extreme heat peaked in Chicago yesterday, where the temperature hit 100° at Midway Airport and the Chicago Lakefront station. Rockford, Illinois hit 100°, the first time in 22 years that city had seen 100° temperatures. Detroit is expected to hit 100° for the first time in sixteen years today, and I think I'm going to skip the Ann Arbor Art Fair! New York City and the mid-Atlantic states are expected to be near 100° on Friday. The forecast high of 103° in Washington D.C. for Friday is just 3° below the hottest temperature ever recorded in the city, 106°. The heat will continue in the mid-Atlantic states through Sunday, then ease on Monday when a cold front is expected to pass through. Wunderground's climate change blogger Dr. Ricky Rood has some good insights on the current heat wave in his latest post. A few notable highlights from this week:

Omaha, Nebraska has been above 80° for a four-day period beginning on July 17. This is the 2nd longest such stretch on record, next to the 8-day period that ended July 25, 1934. Multi-day periods when the low temperatures do not cool off below 75° are associated with high heat wave death rates.

Amarillo, Texas recorded its 26th day of 100° temperatures yesterday, tying the city's record for most 100° days in a year, last set in 1953. Record keeping in the city goes back to 1892.

Minneapolis, Minnesota, recorded its highest dew point ever, 82°, on Tuesday. The heat index hit a remarkable 118° in the city, which tied July 11, 1966 for the highest heat index on record in the city. Minnesota's all-time highest dew point temperature of 86° was tied on Sunday, in Madison. The previous record was in St. James and Pipestone in July of 2005.

The latest National Weather Service storm summary has a list of cities where the heat index exceeded 100° yesterday.

Figure 1. On Wednesday, heat advisories for this dangerous heat wave covered portions of 33 states plus the District of Columbia, an area with 141 million people--about half the population of the U.S.

Tropical Storm Bret no threat
Tropical Storm Bret continues to struggle with high wind shear of 20 - 30 knots, and high shear is expected to affect the storm the remainder of the week. The combination of high wind shear and dry air nearby should act to destroy Bret by Sunday, and the storm is not a threat to any land areas.

Tropical Storm Cindy forms
Tropical Storm Cindy formed yesterday 600 miles to the east of Bermuda. Cindy's formation was 24 days ahead of the usual formation date for the third named storm of the Atlantic hurricane season, which is August 13. This year has the most early season activity since 2008, when Hurricane Dolly got named on July 20. Wind shear is a moderate 10 - 20 knots, and is expected to remain moderate for several days. However, Cindy has moved over cool ocean waters of 25°C this morning, and this temperature is 1.5°C below the threshold of 26.5°C that tropical storms typically need in order to maintain their strength. With Cindy predicted to move over waters of just 21°C by Friday morning, the storm doesn't have long to live. Cindy is not a threat to any land areas.

An African wave worth watching
An African wave near 12N 50W, 700 miles east of the Lesser Antilles Islands, is moving west to west-northwest at about 15 mph, and is generating a limited amount of heavy thunderstorms due to the presence of a large amount of dust and dry air from the Sahara. This wave will spread heavy rain showers and strong gusty winds to the northern Lesser Antilles beginning on Saturday. The wave has a modest degree of spin to it, and is under low wind shear, 5 - 10 knots. Once it finds a moister environment near the Bahama Islands early next week, it could develop. Of the latest 00Z and 06Z runs of the four reliable models for predicting formation of a tropical depression, only the NOGAPS model shows development of the wave. The NOGAPS predicts the wave could attain tropical depression status on Wednesday, just off the coast of South Carolina. The other models generally depict too much wind shear over the Bahamas for the wave to develop. The eventual track of the wave once it reaches the Bahamas early next week is uncertain; there will be a trough of low pressure located off the U.S. East Coast that will be capable of turning the wave to the north, along the East Coast. However, it is also quite possible that the wave would be too weak and to far south to feel the influence of this trough, and instead would enter the Gulf of Mexico.

Figure 2. Morning satellite image of Hurricane Dora.

Hurricane Dora in the Eastern Pacific close to Category 5
Hurricane Dora in the Eastern Pacific put on an impressive burst of intensification over the past 24 hours, and is now a very impressive Category 4 storm with 155 mph winds, just 1 mph short of Category 5 status. Dora is expected to move parallel to the coast of Mexico, and should not cause any major trouble in that country. Dora is the second major hurricane in the East Pacific this year; Hurricane Adrian topped out as a Category 4 storm with 140 mph winds in early June.

Think cold. Way cold!
Those of us sweltering in today's heat would do well to consider that on this date in 1983, Vostok, Antarctica shivered at -128°F--the coldest temperature ever measured on Earth. The low tonight in Vostok is expected to be a relatively balmy -80°F.

Jeff Masters

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Member Since: November 6, 2010 Posts: 14 Comments: 9150
I wonder what Cindy and Bret will do to our friends in Europe..
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OK, now I need to go to Google Maps to find the name of the poor little island out there about to get nuked. Never knew it was there!
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Quoting floodzonenc:

Welcome! Was that last paragraph from your local NWS office? If so, LOL @ the use of the term "ballistic".

Some years ago, one of the lesser football teams here in Scotland beat the biggest team in the land 2-0 in a cup match. Inverness Caledonias Thistle vs Celtic. ICT are known simply as 'Caley' to their fans.

The next day, the newspaper headline was -

Super Caley Go Ballistic, Celtic Are Atrocious

I thought that was brilliant.
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Note to Webmaster:

Current page layout for wxunderground.com goes kaflooey in Opera Webrowser, but looks fine as ever in Firefox.
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Quoting sunlinepr:

Tradewinds in the Caribbean move heat waves away... We can cool off easily cause we're 100 x 35 surrounded by water...

Yeah, and in fact, I have seen it hotter here in Fairbanks, Alaska at 65N latitude than Puerto Rico on a few days this summer.
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Cleared out her eye on the last 2 frames, migh get cat 5!
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Quoting alfabob:

Monsoon trough was elongated from mid-Africa to mid-tropical atlantic, which is where it originated from. Aided in early development since monsoon winds are more productive than ITCZ winds, thus monsoonal-wave. Obviously there's no monsoon trough by it now, but looks reasonably organized for the size.
This wave originated awhile ago way back over eastern Africa. Looking at a hovmoller diagram, I'd say it originated around July 7/8 around 35E

Granite, the monsoon trough which was elongated across the eastern Atlantic at one point, did aid the tropical wave. However, the wave did not originate there.
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Member Since: July 15, 2006 Posts: 195 Comments: 61068
Similar eyes

Isabel, N RD& PR
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Quoting 47n91w:

A cold front moved through last night across Lake Superior and has brought drier air and cooler temps to the region. 82 degrees for a high today after 97 degrees yesterday and a heat index of 113. I was under a Excessive Heat Warning for the last five days. My local NWS office uses this criteria for issuing excessive heat warnings:

issued for a 24-hour period where the heat index exceeds 110 for 3 hours or more during daytime and statys at or above 80 at night

I know some offices tweak their guidelines for things like windchill and winter storm criteria. I wonder if the criteria for heat is the same?

Amazing that we were next to the big lake and STILL had that happen!
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Member Since: July 15, 2006 Posts: 195 Comments: 61068
Quoting WeatherNerdPR:

OK, HOW is it possible for it to be hotter in MICHIGAN than in Puerto Rico?

Tradewinds in the Caribbean move heat waves away... We can cool off easily cause we're 100 x 35 surrounded by water...
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hello all, i am a long time lurker who has been stirred into action as the atlantic basin starts to twitch. i wish everyone a active but safe season. I appreciate all your comments, since i don't have a very big chance of seeing a hurricane up here in CT, i live vicariously though you.

we haven't got a lot of rain up here in CT this year but the latest forecast out of Albany has me excited for some relief form the heat..97.2 at 4:00pm. just to let you know, that is very very hot for here.

...Convective cloud cover noted in mountains on
satellite imagery...and terrain can also be a focus for convective
initiation. Any thunderstorms could go ballistic...as stated
earlier...due to the respectable instability and relatively strong
wind fields through the boundary layer.
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Damn is it hot outside.It's a sweltering 104 on my themomoeter and it feels like 119 outside.I only went outside for five minutes and already started to sweat beads of sweat like a sinner in church.
Member Since: August 14, 2010 Posts: 12 Comments: 20703
Quoting OCF:
A question that's almost local for me in Southern California: when Dora collapses over colder water (as it will), which way will its mid-level moisture and instability go? Northeastward across Mexico any maybe even into Texas? NNE to enhance the AZ/NM summer monsoon flow? Staying over water? Or maybe even N to NW to give coastal Southern California an unusual chance for summer showers?
Right now, that looks unlikely. Models are in strong agreement that Dora will be steered NW by the ridge over North America. This will keep Dora well offshore from Baja and allow it to fizzle out at sea over the cool waters (and resulting dry, stable air mass).

A few ensemble members, and even the CMC operational run, try to take the storm NNW, allowing it to traverse the Baja peninsula. This solution would bring the remnant moisture and vorticity up to our neck of the woods, allowing rare thunderstorms to form over the coastal regions of Southern California.

Unfortunately (for those looking for Dora to make it to SoCal...I realize this is fortunate for Baja), this solution is very unlikely as the models are in strong agreement that the ridge currently centered over central US will build westward. In the process, Dora will be unable to take a northerly track toward Baja/Southern California, and will instead head NW. However, although Dora herself will head way out to sea, she will pull deep tropical moisture northward which will further enhance monsoonal flow over the SW US. Additionally, it should also be noted that as the ridge builds westward, flow over Baja and Southern California will turn more South Easterly, allowing monsoonal moisture to head our way. This will increase moisture in the mid levels of the atmosphere, which may allow for some afternoon thunderstorms over the mountains around early next week.
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Observed at: Toronto Pearson Int'l Airport
Date: 4:00 PM EDT Thursday 21 July 2011
Condition: Partly Cloudy
Pressure: 29.65 inches
Tendency: rising
Visibility: 15 miles
Air Quality Health Index: 4

Temperature: 99.3°F
Dewpoint: 74.7°F
Humidity: 46 %
Wind: W 20 gust 31 mph
Humidex: 119
Member Since: July 15, 2006 Posts: 195 Comments: 61068
Ummm...Hello...This is Alice. Am I in wonderland or wunderground, or both?
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400. DFWjc
Quoting prcane4you:

Who cares about Cindy?

The people in the Iceland or the British Isles
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Even though Florida is HOT today in the 90's with hunidity at near 100% and dewpoints in the 70 and 80's because it has oceans on both sides albeit the oceans are relatively warm the sea breeze does help control our tempuratures. We have afternoon t-storms usually on one side of the state on any given day because of the sea breeze. Temps after and sometimes before a t-storm drop very sharply sometimes into the 70's. It is very dynamical weather in So Fla especially. I will miss this when I leave here. I think....
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Member Since: November 6, 2010 Posts: 14 Comments: 9150
Quoting PalmBeachWeatherBoy:
quick-curious question about the "heat wave": Why are their never any heat advisories in florida? is it because temperatures this high (it is currently 94 degrees with 104 degree heat index in west palm beach)are not far from normal?

also in the winter, florida receives similar "cold weather advisories" when wind chills reach the 30's but northern states do not.

Tallahassee NWS did issue heat advisories a few weeks ago when we had a string of several really hot days here and D. M mentioned it in one his blogs; our Airport had a record 105 reading on that particular afternoon.................The typical advisory then talks about hydration and outside activities in the early morning/late evening, etc....
Member Since: August 8, 2006 Posts: 0 Comments: 11976
Quoting P451:
As the huge stubborn high continues to bake the US in heat....

Sheesh, this sounds like we've got an after-school special "When Weather, Gone Wild"
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Quoting DestinJeff:
378 ...

yeah forgot about that. Or is STAY SAFE? I never can remember.
Depends on the weather, and if there are cashews involved...
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Member Since: November 6, 2010 Posts: 14 Comments: 9150
Baltimore, Inner Harbor
Lat: 39.28 Lon: -76.61 Elev: 19
Last Update on Jul 21, 2:54 pm EDT


103 °F
(39 °C) Humidity: 41 %
Wind Speed: Calm
Barometer: 29.80" (1009.1 mb)
Dewpoint: 75 °F (24 °C)
Heat Index: 117 °F (47 °C)
Visibility: 0.00 mi.
More Local Wx: 3 Day History:

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Cindy has been sporting an eye all morning, as such if it was closer to land it would probably be a hurricane.
Member Since: July 8, 2005 Posts: 259 Comments: 25342
Quoting yonzabam:

I live in a very cool part of the world, but I know heat advisories are mainly aimed at people not acclimatised to extreme heat. Those are the ones most likely to die.

So, Michigan may issue heat advisories even though expected temps there are below those expected in Florida or Texas.

A cold front moved through last night across Lake Superior and has brought drier air and cooler temps to the region. 82 degrees for a high today after 97 degrees yesterday and a heat index of 113. I was under a Excessive Heat Warning for the last five days. My local NWS office uses this criteria for issuing excessive heat warnings:

issued for a 24-hour period where the heat index exceeds 110 for 3 hours or more during daytime and statys at or above 80 at night

I know some offices tweak their guidelines for things like windchill and winter storm criteria. I wonder if the criteria for heat is the same?
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-80 sounds pretty good right now. These popcorn storms like bret and Cindy make me nervous cause later in the season they will move west, not east.
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Be back later...
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Baltimore WeatherSave This Location Updated: Jul 21, 2011, 3:25pm EDTUPDATE DATANearby TruPoint Locations: Baltimore-Washington I... | Mt. Royal Cultural Cen...

Partly Cloudy
Extreme heat index. Outdoor exposure should be limited.
Clear Mostly Sunny Isolated T-Storms
Feels Like: 118°

Oy, I know this is what Baltimore feels like in the summer, but this is crazy. And August isn't even here yet!

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Quoting DestinJeff:
Somebody alert the Storm Whisperer (ike)! We may need his skills in about a week or so.
We all need to BE SAFE!
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My forecast for the 5 pm update:
40 mph
1006 MB
NE to ENE at 11 mph

65 Mph
995 MB
NNE at 30 mph
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HPC Sea Level Pressures and Fronts.3-7 day forecast

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Dr. Jeff Masters' WunderBlog


Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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Afternoon clouds over Southwest Puerto Rico
Storm clouds gathering over Half Dome
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snowman at Yosemite Falls