12 August 2016

Brutal Heat For the Eastern Seaboard This Weekend.

Posted by Dan Satterfield

Heat warnings cover the Eastern Seaboard for the weekend.

Heat warnings cover the Eastern Seaboard for the weekend.

Dew points above 70 cover the entire eastern U.S. and have even edged into Canada. This is extremely muggy air.

Dew points above 70 cover the entire eastern U.S. and have even edged into Canada. This is extremely muggy air.

A weekend of brutal heat is on the way, from here on Delmarva, to DC, and all the way to New York, with heat index values well above 100. Extreme humidity covers much of the Eastern half of the U.S. this Friday evening, and the high moisture content of the air is pushing heat index values into the danger range. The levels of water vapor in the atmosphere are also keeping the nights exceptionally warm, and this increases the risk of heat illness, since those with no air conditioning get no relief at night.

The weekend will bring more of the same with model guidance this afternoon indicating heat index values near 110 from the Delmarva area, all the way to Long Island, and into Connecticut.

The images (below) show the predicted heat index based on the NOAA 4 km resolution WRF model. This model does a good job of predicting these values, and I’m quite confident that this is about what we will see.

hires_hindex_maryland_26

hires_hindex_nj_49

Even Sunday looks brutal, with extreme heat and humidity into NY and CT.

 

 
The long range guidance shows the storm-track (500 hPa wind flow) easing into an almost early fall like pattern, which should bring the heat down, and the rain chances up, over the NE third of the U.S. The image below is an average of several different model runs. It shows the upper level high weakening and moving into the Atlantic.

gfs_z500a_us_25

This is the wind flow at around 6 km above the surface. Winds follow the black height lines. 588= 5880 meters to reach the 500 millibar level.