14 July 2011
Yes, The Heat is Bad, But It’s Going to Get Worse
Posted by Dan Satterfield
The torrid heat is going to get worse next week.
Much of the Plains is suffering through the hottest summer since 1980 and Texas is enduring a drought that is now called exceptional. In the Southeast the heat index hit 115° (46C) in Greenville, MS. on Wed. and Poplar Bluff in Mo. beat that with 118° on Monday. The heat is being made much worse in the Eastern U.S. by the unusually high amount of atmospheric water vapor. Dewpoint temps. reached 80° as far north as Kentucky on Tuesday, and Richmond, Va. broke it’s all time record high low with 81 degrees (27.2C) on Wednesday morning (records go well back into the 1800’s there).
Instead of a break from the heat, it now looks like it will get considerably worse, with the high temperatures spreading from the Rockies, to the East Coast and into Canada. The NOAA-GFS model is indicating temps. over 40°C (104°F) in Manitoba early next week, and the very high humidity( from wet ground) in the Southeast will mean heat indexes near 115 or higher again.
In the far north, the atmosphere is breaking records as well with the 500 millibar height record at the Pole (using the NCEP reanalysis) was likely broken last week with a height of 5877 meters. The warmer the atmosphere, the higher you have to climb to reach a pressure of 500 millibars, and this is a good indicator of just how warm the troposphere was over the North Pole.(Hat tip to my friend Stu Ostro at the Weather Channel for the image and the heads up.)
If you think this is not nearly as serious as a tornado outbreak or a hurricane, then think again. Heat is likely the number one weather killer worldwide. The urban heat island effect keeps night-time temperatures in cities even warmer and there is evidence that this is an important factor in heat related fatalities. This warmth of cities was first noted by Luke Howard (He invented the classification system for clouds) in a paper published in 1818.
The image below is the forecast of the 500 mb heights, and how far above and below the average they are for the date. The heights are forecasted to be 200 meters above normal across southern Canada by the middle of next week. Almost all the numerical weather prediction models are indicating the same thing from the Canadian GEM, to the European ECMWF, and this increases the forecast confidence considerably.
The incredible Arctic warmth is certainly seeming to have an effect on the Arctic sea ice as well. 2007 saw the biggest melt of arctic sea ice on record, and it is beginning to look like this year may bring a new record low.
I’ve seen heat index charts before where on one vertex they have the humidity and then on the other actual temperature and in the middle what temperature it feels like to humans. I was wondering if you understand what I’m talking about and know where I can find it on the internet. I’ve done searches and get the formula but not the chart. I find it is so much easier to look at that chart than it is to do all those calculations.
With the high temperatures and humidity we’ve been having I’ve been curious as to what the heat index has been in our area.
Just Google heat index chart and you should find plenty. One caveat is that the heat index, nor the wind chill is “what it feels like”. They are just indexes that measure heat loss or lack of same. 40C feels like 40C no matter what the humidity but it is far more uncomfortable to the body when the amount of water vapor in the air is high.