Beware the MJO! It will flood California with a “Pineapple Express” and leave most of the Midwest high and dry.
The MJO, Madden Julian Oscillation, is a harmless looking little pool of wind and water drifting in the Tropical Pacific. It doesn’t look like anything special. But look out! It can shape hurricanes and droughts, floods and blizzards.
Currently California is being blasted by storm after storm. A powerful jet stream is carrying the tropical moisture from Hawaii to the West Coast, thus the name Pineapple Express. The direction of the jet stream and the blast of moisture is no surprise, however. It occurs every time that the MJO shifts into position.
The Pineapple Express not only drowns the West Coast, it shapes weather further east.
The MJO has two patterns: wet and dry. The wet types are areas where tropical winds are unusually quiet and the ocean surface is still, soaking up sunshine. It becomes unusually warm and heats the air above it. Moist air holds more water and as the hot air rises, it creates heavy rainfall. Winds blow out from the equator to the poles so a wet pool of rain stretches out from the MJO. As it drifts to the east, the MJO finally is south of the Hawaiian Islands. The Pacific jetstream catches the plume of moisture and carries it northeast. When the hot, wet air hits the cooler land, the tropical moisture pours itself out in a series of flooding rains. In the mountains, the Pineapple Express creates blizzards and avalanches.
The Pineapple Express causes floods and blizzards in the Western US and Canada. SOURCE − Walter Siegmund
The results can create weather on the West Coast as damaging as a hurricane on the East Coast. It is like a high-pressure fire hose blasting the coast with water. Like a loose hose on your lawn, it whips around, now blasting Seattle, next hitting San Francisco.
However, the impact is not limited to the West Coast. There is a lot of pressure in that stream of moisture as it blasts eastward. The jet stream carries weather patterns northeast. Moisture blasts the Northern Rockies and Canada’s Prairies. Unfortunately, the moisture is blasted away from the Midwest. Most of our Northern Plains are left high and dry and the jetstream normally doesn’t re-enter the US until the Great Lakes.
The Pineapple Express not only drowns the West Coast, it shapes weather further east.
The good news is that the impact of these rains will linger. Western reservoirs will refill. The snowpack will build and, the springtime melt will feed rivers from the Sacramento to the Missouri.
The first blog I ever wrote for the Old Farmer’s Almanac was about the Pineapple Express, so I will end this blog as I did that one.
Have you ever “ridden” the Pineapple Express? Do we have any California fans? If you'd like to share your thoughts, I'd love to hear from you. (Just post comment below.)
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I am a citrus farmer in Central CA. We are always on the fringe: either the southern fringe of the northern storms, or the northern fringe of the southern storms. We had a very dry and very warm fall this year. We're still below historical averages for rainfall as of 12/10/12, but at least the weather has cooled off...hoping no major freezes for our citrus this winter! We're also hoping the Sierra Nevada's get a good snowpack - that's our summer water supply! Thank you for your blogs!
Good luck on the crop! I love California oranges. It looks like the Sierra Nevada has a fairly good chance of getting a good snow pack.
I've been living in California for almost 20 years (a NH transplant), in the San Francisco Bay Area. Our rainy seasons during that time was pretty consistent. However, just moving up to the Sierra foothills this past summer, we have been bombarded by rain over the past six weeks. The longest duration of the heaviest rain I have ever witnessed in my young 50 years, was about two weeks ago. A fairly dried up pond on our property, filled up to about 10 ft deep within a weekend of this rain. I fully support this pineapple express "business" but now, I would like a big dose of snow, please! Let's bring the temps down a bit Mother Nature!! :-D
Yes, there is less erosion and better river runs if the moisture is stored as snow pack in the mountains. (Not to mention, better skiing!)
I live in the west and during the first week of December it has been quite wet. I love the rain because late summer through fall we havent been in the way of rainfall. I'm not too crazy about the severe weather with the storms but the pineapple express gave us a GRREEAT soaking. Its what we needed in the thirsty western United States.
I have to admit, seeing the eastern US being so warm and dry is sad. I know how it feels to have winter cancelled. We didnt have one either last year. I hope old man winter will stay not only here, but in the eastern US as well. Im so sorry folks!! Dont give up on winter though, its still fall and winter is still a matter of 2 weeks away. You'd be amazed of how much things change between now and Christmas. I will check weather forecasts tomorrow, the US doesent need warm and dry. I've seen enough!
I'm going to be driving in the Midwest tomorrow. (Columbus, Ohio!) I want it to be warm, dry and boring for two more days, then let the blizzards roar!
Im very very very ticked off at this weather. I was out west in southern Oregon at my friends house last week, see they were being bombarded with storms like you said, caused by the Pineapple Express but back home in Indiana, we havent seen a drop of precip in i dont know how long. In the lower midwest and mid atlantic states there isnt any signs of snow. It stayed in MN, IL and farther north. Its supposed to get cold BUT temperatures will rebound back above normal. I live in a small rural town in southeastern Indiana , the weather seems to be the talk of most people. We're all sick of this warm weather. Its December, when is winter coming in for good? Im getting to the point where I may just give up on winter. Do you still expect this winter will be real? I just want winter back :'( is that too much to ask for?
Lol it looks like all of us want a winter on the Old Farmers Almanac!
I just read the latest science on the Arctic Oscillation and they were predicting a negative AO that would bring a frigid, stormy winter in the Midwest. Now if reality would just match the models.
Here in eastern Texas it has been quite a weather year. 2 years in a row Texas has been dying and roasting over the summers of 2011 & 2012. No matter how much it rains, it would be nice if the MJO could help all of us in the south. We need the rain very very badly, basically the whole US was under drought this year in 2012 but theres one benefit to this though, we in the United States have the urge to help one another in tough times. For instance, the derecho that hit the Mid Atlantic states like Maryland and Virginia, I actually saw people donate money to the tragedy there as they were suffering through a tough heat wave without power. During Sandy, seeing them lose everything they had, It brought me to tears to see it. It was heartbreaking, I've been through hurricanes, tornadoes.. Ive seen it all in my neck of the woods. Now that winter is here (almost) can we please give our fellow easterners the snow they want? I want to close out 2012 with a real winter as well. No more fake winters, mother nature ripped us off last year. However, I believe things will recover. 2013 is a new year, we can start it off right with snow in the east, rain in the Texas panhandle, storms in the west and the mighty Mississippi filling up with water
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