I remember this day 5 years ago quite well. The obvious forecast was for a hot day, but I don't think anyone in their right mind saw what was coming. After all, who forecasts an all-time record high temperature? Some of you know we have the ability to communicate with the NWS through a chat room. It's main use is in times of severe thunderstorms, but I thought I would log in as the heat was getting out of hand. Former NWS meteorologist John Robinson was also logged in at his NWS desk. He kept giving a temperature update every few minutes. For temperatures to get up to 114 degrees, the dew point value must not be elevated. To start the day, those dew point values were crazy high, but started to slowly come down throughout the day most likely due to a process called "mixing". Drier air was mixing down to the surface causing the dew point value to drop significantly. In the chart below, you can see that happening. As the dew point dropped, the temperature soared. I remember seeing John type: 110 degrees, 111 degrees, 112 degrees. I thought we were done and we maxed out, but he kept typing as the temperature rose to an astounding 114 degrees just before 3 PM.
With the temperature that high, moisture started to build once again and the heat index sky rocketed up to 120 degrees.
Here's all the data below. Notice the early morning temperatures were already in the mid 80s!
|Hourly temperatures August 11th, 2011. The 114 degrees was recorded shortly before 3PM. Look at the dew point/humidity drop as the temperature rose. Then the moisture levels jumped and the heat index did as well.|
|August 2011 temperatures. After 8 straight days of triple digit heat, it finally broke on the 9th.|