Goodbye Triple R, Hello Pineapple Express

January 29, 2016
Pineapple Express
NASA

Ever heard of the Pineapple ExpressCalifornia collects weather patterns with odd names.

Does it have a drought? Blame the Ridiculously Resilient Ridge (Triple R). Did it just get super heavy rainfall? That's the fault of the Pineapple Express. Fortunately for the drought stricken state, the Triple R has faded and it has huge, wet Pineapples in its future.

Triple R: the high pressure area that blocked California rainfall for two years.

The Ridiculously Resilient Ridge was the name weathermen, starting with Daniel Swain of The California Weather Blog, gave to an obnoxious high atmospheric pressure pattern that formed off the West Coast. (A “ridge” is another name for an area of high pressure.) High pressure patterns block rainfall; think “High and Dry”. Storms veer around the high pressure areas. Normally a “High” parks off the West Coast in summer and California has a dry season. Then it drifts away and the West Coast has a rainy winter.

In 2013 and through most of 2014, the “High” refused to leave. It blocked rainfall and California had a record-breaking drought. Storm after storm was turned away by a ridge that resisted movement. It stayed put for a ridiculous length of time, earning its Triple R name.

This November, the ridge finally left. There is nothing blocking the rainfall. Yeah!

Here comes an atmospheric river to pour rain on the West Coast

Enter the Pineapple Express!

Occasionally a long stream of tropical moisture gets steered away from the tropics. These are called atmospheric rivers. Typically these “rivers” are huge bands of water vapor, 250 to 350 miles-wide that carry as much as 300,000 tons of water. This is 7 to 15 times as much as the mouth of the Mississippi River. On any given day, these bands of water vapor account for more than 90% of the movement of tropical moisture north and south.

The ones that usually hit the West Coast pass through Hawaii first, earning the name “Pineapple Express”. They are especially heavy when the Pacific is experiencing El Niño style warmth, like it is right now. In the past couple of years, the Triple R blocked these rivers of rain. Now, there is nothing in the way.

The Pineapple Express is bringing abundant rain to thirsty California.

So congratulations, California. Nothing is blocking that desperately needed rainfall. So grab your umbrella and watch out for pineapples!

 

About This Blog

The column, “Weather Whispers,” is authored by James Garriss and Evelyn Browning Garriss, historical climatologists and weather addicts!  Whether you enjoy the science of weather or the fascinating folklore or just fun weather phenomena, it’s probably covered by these weather watchers!

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