Saturday, July 4, 2015

Long Range Lookout: Cooler Than Normal July Ahead

This post is dedicated to the servicemen and women who are serving our country, who have served our country, and those who have made the ultimate sacrifice for our country.

It appears that a cooler than normal July is on the way for the nation.

We'll begin by looking over shorter-range indicators; in this case, the Typhoon Rule.

Tropical Tidbits
The above image shows forecasted 500 millibar anomalies over the West Pacific. Here, blues indicate negative height anomalies, symbolizing a trough or storm system in the area. Oranges and reds correlate to positive height anomalies, indicative of warmer and quieter weather.
This forecast is valid for July 14th, and we see a system just southeast of Japan, making its way north and east. This system was previously a typhoon, which looks to develop in coming days further to the south. As the typhoon approaches Japan, it will curve and head out to sea. Using the Typhoon Rule, we can expect a cooler bout of weather about 6-10 days after this happens. Recognizing that this forecast is for July 14th, we can extrapolate that to forecast a cool-down around July 20th to 24th, probably spilling over those dates a bit.

However, it's also likely that the entire month will end up cooler than normal for many in the country, due to what is happening in the Central Pacific.

A quick overview of the columns, going from left to right: The date for the data, the daily barometric pressure reading in Tahiti, the daily barometric pressure reading in Darwin, the daily value of the Southern Oscillation Index (SOI), the 30 day averaged SOI, and the 90 day averaged SOI.
In a nutshell, when the SOI is negative, El Nino conditions are favored in the United States in the following couple of weeks. We see that the SOI has been consistently negative since June 19th, and it's no coincidence that the United States has been predominantly cool since late June.
You can see how El Nino conditions, which are signaled by a negative SOI, make for a cooler than normal summer in the composite chart below:

Typical temperature anomalies during an El Nino summer
Since we remain in a negative SOI state this 4th of July, I'm expecting the rest of the month to end up cooler than normal for much of the country. Those in the Southeast and East could see slightly warmer conditions, however.

To summarize:

- A cooler than normal month of July is expected for much of the United States.



Anonymous said...

You have no idea how much you've been missed!

jack gondela said...

It is worth having a cool July to have you back, Andrew. We've missed you.

Anonymous said...

welcome back Andrew!

Anonymous said...

I hope you really do know how much you have been missed by those of us who love Winter weather. I am personally really interested in how the expected El Nino will effect the Northern California area. Have miss your expertise so much Andrew!

Anonymous said...

Hi Andrew and welcome back! What do you see happening with the El Nino-will it bring rain and snow back to California? I have so missed your deep analysis. Come and speak to us when you can and I hope you had a nice 4th. Was watching a very old movie on the 4th of July. It is called appropriately 1776. It is a musical and there are some songs in it but, it is actually factual too. Shows how hard those inspired men in congress of 1776 had to work to get an up vote from all in to get the Delaration of Independence from Britain for our United States- They worked forever to get it passed by all and watching this you have to be amazed that they did manage to get it through. They were brilliant men and I doubt we see the likes of them in our lifetime. Great, great movie. July 4th would not exist without them!

Ridley said...


Anonymous said...

Nice to see you back, Andrew