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Posted at 01:24 PM ET, 03/15/2013

Cherry blossom peak bloom forecast from Capital Weather Gang: April 5


Cherry blossoms with the Washington Monument, March 19, 2012. (Kevin Ambrose)

What a difference a year makes. Last year’s record-warm March led to a tie for the third earliest cherry blossom peak on record on March 20. This year, cooler than average weather is likely to push the peak bloom back considerably. We project blossoms will peak between April 3 and April 7, or around April 5.

Our forecast date is near or slightly after the long-term average peak bloom date of April 4. The earliest bloom date on record was March 15, 1990, and latest was April 18, 1958.

Already, this year’s cherry blossoms are behind in bud development compared to last year. In 2012, green buds first appeared on February 29. That milestone wasn’t reached until March 11 this year.

Our April 5 forecast for 2013’s peak bloom departs from the official prediction of the National Park Service. It announced last week that the blossoms should peak between March 26-30.

Our delayed outlook results from an expectation that cooler than normal temperatures will dominate the second half of March.

Historically, there is strong relationship between March temperatures and the peak bloom date. I analyzed bloom date and March average temperature data and found:

* In years March is 0-2 degrees colder than average (around 47 degrees), the peak bloom date centers around April 4

* In years March is 2-4 degrees colder than average, the peak bloom date centers around April 8

* In years March is more than 4 degrees colder than average, the peak bloom date centers around April 12-13

Related: D.C.’s cherry blossoms have shifted 5 days earlier: what about global warming and the future?


Through the first half of March, the temperature in Washington, D.C. has been about half a degree below average. Long range models for the second half of March generally indicate temperatures should end up around 4 to 5 degrees below average.


Temperature difference from average for March 14 through 29 on the GFS model (ensemble mean) (WeatherBell.com)

Our assumption is that March will end somewhere in the neighborhood of 2 to 3 degrees below average - and that’s the primary rationale for our projected April 5 peak bloom date. Obviously, there is some uncertainty here and if our temperature forecast is off, so too will our bloom date prediction.

Historically, the date of the peak bloom accelerates forward when there is a stretch of unusually warm days and, especially, mild nights - when temperatures fail to drop below the 50s. We see little potential for any prolonged warm weather spells this month, although we can’t rule out a fleeting bout or two of spring fever.

For its part, NOAA’s Climate Prediction Center also forecasts a cold close to March over much of the eastern two-thirds of the country.


Temperature outlook 8-14 days from now (NOAA)

Last year, we correctly (on March 12) foresaw a prolonged period of unusually warm weather in mid-March and forecast a peak bloom date of March 18-22 (NPS was forecasting a peak bloom of March 24-28 at the time). The actual peak came on March 20.


GFS forecast for temperature difference from normal on March 15-22 in 2012 and 2013. (WeatherBell.com via Brad Panovich)

This year, the prevailing weather pattern in the mid-to-late March is essentially opposite last year. Whereas last year we had a huge ridge (or bump) in the jet stream over the eastern U.S., this year a big dip in the jet stream is forecast in the same locations. This dip in the jet stream, associated with a strongly negative phase of the Arctic Oscillation, is forecast to allow unseasonably chilly air to episodically flow southward out of Canada.

Links:

Ten days of cherry blossoms (PHOTOS, 2012)
Cherry blossoms bursting out (PHOTOS, 2012)
Cherry blossoms with an overcast sky (PHOTOS, 2011)
Washington’s cherry blossoms in the snow (PHOTOS, 2011)
A cherry blossom bird’s-eye view (PHOTOS, 2010)
Cherry Blossoms Wind Down as D.C. Greens Up (PHOTOS, 2009)
Cherry Blossom Morning (PHOTOS 2009)
Washington D.C.’s Cherry Blossom Bloom Begins (PHOTOS, 2009)
Photography: Falling Blossoms & Spring Scenes, Kevin Ambrose (2008)
Photography: A Blooming Good Time (2008)
Photography: Glorious Cherry Blossom Sunrise (2008)
Photography: Cherry Blossoms by Night (2008)
Photography: Flying High as Spring Blossoms (2008)

By  |  01:24 PM ET, 03/15/2013

Categories:  Capital Weather Gang, Cherry Blossoms, Latest, Local Climate

 
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