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Old 12-01-2009, 04:21 PM
 
Location: Just outside of Portland
4,828 posts, read 7,430,496 times
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Due to hit the west coast by the weekend!
Batten down the hatches!
Head for the bunker!
We may be in for some interesting wet weather!
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Old 12-01-2009, 09:07 PM
 
Location: Portland, OR
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Sorry,

I tried to Wikipedia your Madden-Julian Oscillation, and I cannot make heads or tails of it. It reads like this is some sort of Monsoon rain storm that hits Northern California and southern Oregon.

I checked NOAA web forecasts, and couldn't find any reference to a MJO event comming up in the next 3 days or so. When does you sources predict the event making landfall?

Phil
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Old 12-02-2009, 07:52 AM
 
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I guess making my first post on this topic might show my true colors as a nerd. I normally lurk around here. Although I don't currently live in Portland, I'm always keeping my eyes open for jobs out there since I love the area. I thought I'd try to give a quick explanation of the Madden-Julian Oscillation (MJO) (qualifications: Master's degree in atmospheric science, currently a meteorology research scientist with NASA).

The MJO is more than a particular storm, and in fact, in weather forecasts that you read about, you will probably never see reference to an MJO event. The MJO is a set of related patterns that develop over the Western Pacific Ocean, characterized by regions alternating, abnormally high and low pressure areas that start of Africa. This area of high/low pressure moves eastward across the Pacific Ocean and b/c of the structure of the atmosphere associated with this MJO event, thunderstorms are typically abundant in the tropical Pacific.

During the winter time, these MJO events are often associate with heavy rains for the Pac NW. As the thunderstorms move east across the Pacific ocean, the jet stream (the winds high in the atmosphere that steer weather systems) often draw moisture from these areas of thunderstorms up towards the Pac NW. This moist, unstable air, combined with areas of low pressure moving across the region set up a situation for heavy rain and storms. So, it's not an MJO event that "causes" the storm, but the presence of an MJO event (which happens along the equator in the Pacific) can provide some of the necessary ingredients for a storm to occur.

Sorry for the long winded post as my first:-) Looking forward to hanging around more often.

Matt
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Old 12-02-2009, 09:14 AM
 
Location: Portland, OR
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Matt:

Welcome! and thanks for the explanation.

but two questions for clarifications:
-- The Pac Ocean MJO that is out there now, does (or, will) the MJO actually make landfall along South America's West Coast?

-- Since the storms we will see in the PNW are in fact 'derivative' storm fronts (from the MJO event in the Pacific tropical zone), wouldn't the ocean currents be more likely drive these 'derivative' storm fronts into the California Coast rather than Oregon and Washington states? (Yes, the jet stream, I understand; but doesn't the currents also help drive the Jet Stream?)

Last edited by philwithbeard; 12-02-2009 at 09:17 AM.. Reason: forgot to link my question: currents to jetstream
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Old 12-02-2009, 01:29 PM
 
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Phil,

Thanks for the welcome. Hopefully I'll be around more. I think I'll actually be getting to head out to pdx in February for a conference. But to try to answer your questions:

1. There currently is an MJO "event" nearing the coast of South America. I say "event" because MJO's aren't always easy to "see" on a weather map in terms of clouds/rain/actual weather. Often times, it can be as subtle as an area of low (or high) pressure that isn't easily noticeable. Obviously, those are weaker events, though, and not as likely to influence weather in pdx as much.

2. This is a tough question to answer. If I could answer it completely, they'd pay me a lot more than they do:-) Moisture transfer between ocean and atmosphere is important, but in addition, these MJO events alter the way the jet stream is moving. The moisture from the ocean plays a huge role in weather, but as it evaporates into the air, the weather systems that affect us are moved basically completely by the currents of air high above the earth's surface.

In general (although it's a tough problem! That's why I have a job--there are lots of weather mysteries left to be solved!), periods with strong MJO events moving across the Pacific will be associated with storm systems in the Pacific northwest. In less active periods, you often get high pressure over the northwest and rainier weather in the central US. Again, just generalizations and each situation is different, but hopefully you've learned at least a little:-)

Any recommendations on what I should do when I'm out there in February? I'm looking forward to exploring the city and it's always nice to have some inside info.

Matt
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