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Cherry blossom peak bloom forecast from Capital Weather Gang: April 9

The sun’s setting light casts a soft glow on the cherry blossoms April 9, 2013. (Kevin Ambrose)

Snow is still on the ground, but some milder weather is just around the corner and – before we know it- the cherry blossoms will be blooming.  But given the cold start to  March and more possible arctic chill in the pipeline, some patience is required for blossom admirers in the short run. We’re predicting a later than average peak bloom this year – most likely between April 7 and April 11, centered on April 9.

Our forecast is very similar to the National Park Service’s forecast of an April 8-12 peak bloom period.  Both of our forecasts favor peak bloom at end of the National Cherry Blossom Festival, which runs from March 20 to April 13.

Blossom peak bloom date records have been maintained by the National Park Service since 1921.  The earliest bloom date on record was March 15, 1990, and latest was April 18, 1958.  The average peak bloom date is April 4.

How did we come up with our forecast?

March temperatures are the best predictor for cherry blossom bloom dates.  The strong relationship between temperature and bloom dates is apparent on the chart below.

This March, we expect colder than normal temperatures and that’s the general basis for our bloom prediction.

Through Wednesday, the average temperature in March was running about 10 degrees colder than average in Washington.  Some milder than normal air will reduce that difference from normal early next week, but another round of much colder than normal air could return 8-14 days from now.

Beyond that, long-range models favor near normal to slightly below normal temperatures – but confidence that far out is low.

Capital Weather Gang’s Matt Rogers – a specialist in long-range prediction – projects the month to finish about 2.5 degrees colder than average. In past years when March temperatures were 2 to 3 degrees colder than average, the peak bloom occurred between April 5 and April 12.

“While this March has started much colder than last year, sufficient volatility in the jet stream pattern in the next few weeks will include a few brief warm-ups that should average out the month close to maybe slightly less cold overall vs. last year,” Rogers said. “However, there are no signs of any extended warm periods that would significantly accelerate the blooms.”

Last year, in which March was  slightly colder (3 degrees below average) than we expect this year to be, the peak bloom occurred on April 9.  The bloom might have been even later but a major warm spell pushed temperatures into the 70s and 80s April 7-9.  Sunny, warm days in late March and early April can really accelerate bud bursting (whereas cool cloudy days and cold nights can slow them down).  There’s no way for us to know if we’ll get such a warm spell this year.  We tend to think such a warm push is less likely compared to last year – as this year’s warm weather episodes have tended to be very short-lived, while cold snaps have had more staying power.

Overall, considering we expect this March to be slightly milder than last March, but with less potential for sustained warmth late in the month into early April, we’re predicting the peak bloom to occur around the same time. If we’re wrong about the peak bloom period, we think it’s more likely to occur later than earlier than our predicted range.

Here’s our bloom forecast in probabilities:

Peak bloom April 7-11: 50 percent chance (most likely)
Peak bloom April 12-16: 30 percent chance
Peak bloom April 2-6: 15 percent chance
Peak bloom outside of the above ranges (April 2-16): 5 percent chance

How have our forecasts done historically?

This is the third year we’ve issued a cherry blossom peak bloom forecast.  The last two years we’ve gotten off to a reasonably good start.

Last year, we predicted an April 5 peak bloom date (April 3-7 period) and it occurred April 9.  Our forecast was a bit closer than the National Park Service’s prediction of March 26-30 (at the time we issued our forecast), which it later revised to April 3-6.

In the very warm 2012, we predicted a peak bloom date of March 20, the same day it actually occurred. The National Park Service was forecasting a peak bloom of March 24-28 at the time.

This year we’re on the same page with the National Park Service. We think its April 8-12 projection is a good forecast.

Related links

DC blooms: Where to find cherry blossoms in your neighborhood.

2013 cherry blossom coverage

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)