Temperature Rollercoaster

 Amusement parks are a popular attraction during the summer, and the rollercoaster is still sought by many.  This summer we're in a bit of a temperature rollercoaster.  And that's probably a good thing.  Everyone gets a few days of what they like.  To show what I mean, here's the temperature graph for Spokane Airport.  The dark blue bars represent the daily temperature.  The top of the bar is the high temperature, the bottom is the low.  The warm ups are gradual until they reach the 90s, and then they come crashing back down to around 80 for a couple of days before the next warm up begins.

The reason for this rollercoaster is the jet stream.  We talked about this in our last blog.  The heat has been in the southern states this summer.  The high pressure over the desert Southwest wants to amplify into our area, and does every so often, only to get pushed east and beaten down by a cool low pressure system from the Gulf of Alaska.

Here's the weather map from Thursday morning.  Notice the ridge axis (dashed line) is right over the Inland NW, with the High pressure over the Southwest and Low pressure in the Gulf of Alaska.  This is a hot weather pattern for us.

But by early next week, the jet stream will move that Low into our area for much cooler temperatures.  The high temperatures of the mid 90s this weekend will be replaced by lower 80s on Tuesday and Wednesday.  This will be another dry front, with a few sprinkle showers possible Tuesday morning.  Expect breezy winds on Monday and Tuesday, with little if any morning dew during this time period.  

Our return to hot weather will be a bit delayed this time.  Rather than the cool Low moving east, part of it gets left behind over us.  This will keep our daytime highs in the 80s next week. Wednesday through Friday will have lows in the mid-40s; bundle up.

This pattern change will help the desert Southwest cool off a bit, and start up the Southwest Monsoon (more about that in a minute).  The heat instead will get pushed into the Midwest.  Expect the news stories of Kansas City reaching triple digits during the middle of next week.

But the pattern will eventually reset for more hot weather in the Inland NW.  Here's the weather forecast map for the first of August.  Doesn't that look familiar?  But again, the axis of the hot ridge (dashed line) is to the east of us.  This should keep us from getting really hot, and possibly allow the next Gulf of Alaska low to move our way.

We were speaking about the hot weather over the southern states this summer.  Here's a map showing how cities across the lower 48 rank for July so far.  A red "1" means it's the hottest ever for that location; a red "2" means it's the second hottest ever; a blue "6" means it's the 6th coldest ever.

Clearly the heat has been around the edges, but most notably the Gulf Coast, Florida, Texas and the desert Southwest.  Meanwhile the upper Midwest has had a cool July so far.  As we said, though, all of that is about to flip next week.

We mentioned the Southwest monsoon.  This is an annual weather pattern that brings rain to the desert Southwest each summer.  Moisture from the Gulf of California moves into Arizona and New Mexico, causing wet thunderstorms on most days in the summer.  After a very dry spring, the monsoon rains make July and August the wettest months of the year.

In addition to rain, the cloudiness makes the heat a little more bearable.  But this year, the monsoon is late.  As we said earlier, then weather pattern change that is coming will allow the monsoon pattern to get started.  This will be a welcome relief for folks who live in the Southwest.

We've all heard how hot it has been in Phoenix this summer so far.  And you may think "yeah, isn't it always hot there in the summer?"  Yes, but this has been extra hot.  One way to show this is the consecutive number of days with a high temperature of 110F or higher.  Phoenix broke that all-time record earlier this week, and they just keep adding to it.  The forecast calls for this to continue for the next 9 days.  In other words, they're going to shatter the record from 1974.  You'll also notice that most of the previous heat waves were in June or early July, prior to the start of the monsoon.  In many years, June is the hottest month of the summer in Phoenix.

One more thing to consider.  On Wednesday, the low temperature in Phoenix was only 97F.  And yes, that was an all-time record as well.  Meanwhile, Death Valley remained in triple digits for 92 consecutive hours.