Tuesday, June 28, 2011

Summer BEFORE July 4th?

Summer officially started June 21st. But here in the Pacific Northwest, residents often live by the creed, "Summer actually starts on the 5th of July". It has been a decent start to the Summer here in Portland. A 80 degree day here or there. But even better news is showing up on the weather maps! Let's take a look.

Our first bit of evidence is the 500mb map. This is halfway up the atmosphere and shows us overall ridge (good) and trough (bad) patterns.

Here is the 500mb map valid last night for July 4th around 11 a.m. Look at the ridge that covers most of the West and extends all the way into northern Canada! This is a great set up for a nice stretch of warm, sunny conditions! Other maps re-enforce this fact.

The map above is our 850mb map. We use this map to locate areas of warm air and areas of cold air. We can track their movement with this map. The red contours on the map are isotherms, lines of constant temperature, in degrees Celsius. Temperatures at the 850mb level loosely translate to specific temperatures at the surface. This map, again valid last night (June 27th) shows the conditions for late morning on the 4th. The 15-degree isotherm is just to our east. If we estimate the 850 temp to be about 14 degrees Celsius above Portland, that would translate to an 80-degree day! Plenty of time for it to change, one way or another, but the warm temperature fits the above 500mb map we looked at!
Here is your surface map for the Fourth of July! Looks awesome! Precipitation is nowhere to be seen. Also not the high pressure system out off the southern Oregon coast. That helps send any sort of wet systems well to our north! Any time we see surface pressure around 1020, that means good things. The 1020 isobar (lines of constant pressure) is right in our neighborhood. Average surface pressure is right around 1013. The higher the pressure, the better the conditions!

We have concluded our investigative work! Weather forecasting works like an investigation. Start with one map, and try to find validations on all the others. In our 4th of July case, things are lining up in a good way! Maybe this year, Summer in the NW starts early!

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