Friday, April 21, 2006

Hard Rain Gonna Fall?

Well, not yet, anyway. Despite a nearly stationary front lurking in the vicinity and juicy dewpoints for the season in the mid to upper 50s, rain showers have been slow to penetrate the drought-dogged DC metro area. I encountered a brief shower in the Shady Grove area of Rockville/Gaithersburg early this afternoon, but it was barely enough for a few swipes of the windshield wipers. National Airport reported less than half an hour of light rain in the 2-3pm hour; the total amount was a trace, and Dulles received the same amount. Radar at mid afternoon showed some showers generally eastward from near Charlottesville across the Northern Neck and up and down most of the Eastern Shore.

Live radar loop above, courtesy WJLA. Refresh page to update.

Temperatures are holding in the mid 60s under easterly winds, although National was 2 degrees higher at noon with 67.

Mr. Model, the PM edition, (or at least the first one out of the gate) is still insisting on getting some rain onto the ground by 8pm tonight, but from the looks of things right now, the best chance for some drought-denting, if not drought-busting, rain in the next 36 hours looks like the period from late morning Saturday through Saturday evening. The heaviest amounts, however, are predicted to the northwest of the District. The graphic to the right shows the model forecast of the 12-hr precipitation ending at 8pm Saturday. The amounts in blue range up to 1.25"

Tonight and Tomorrow

Lows tonight under overcast skies will be in the mid to upper 50s. The chance of showers will increase from 60% through this evening to near 100% by tomorrow morning. The best chance of showers this evening is southeast of the Beltway. Showers and possibly thunderstorms are likely tomorrow with highs in the mid 60s.

Which Way the Wind Blows

Regular readers may recall that we remarked last year on the fact that Bob Dylan's music is heavily influenced by weather imagery. Yesterday's WaPo Reliable Source column revealed that Dylan's debut as a disc jockey on DC-based XM Satellite Radio May 3 will feature an hour of weather-related music. Some of the tunes, according to the Reliable Sourceresses, include: Muddy Waters's "Blow Wind Blow," "Just Walkin' in the Rain" by the Prisonaires and "Place in the Sun" by Stevie Wonder. The XM press release gives some more details, including the fact the Stevie Wonder tune is sung in Italian. Track lists will be posted on a special Bob Dylan web page on the XM site.

Thursday, April 20, 2006

No-protest Weather Running Out

There was nothing to protest about the weather for the Chinese president's visit to the Nation's Capital today. The string of exceptionally fine spring days was extended with temperatures at or above 80 by mid afternoon throughout the metro area.

As Josh explains below, however, our luck will be running out starting tomorrow. A low pressure area moving northeastward from the Tennessee Valley will bring clouds and the threat of showers by mid-day tomorrow, along with significantly cooler temperatures.

Photo of brilliant blue sky over Georgetown yesterday by photographer, Kevin Ambrose.

Tonight and Tomorrow

Increasing high clouds tonight will keep low temperatures in the upper 50s city to the low 50s in the colder 'burbs. Skies should be overcast by tomorrow morning with showers arriving by early afternoon and continuing into tomorrow night. There is an 80% chance of showers and possibly thundershowers by evening; highs will be in the upper 60s.

Above-Average April

As Matt noted a couple of days ago, this month so far is another in a long series of warmer than normal months. The chart shows that only 5 of the daily highs and 4 of the daily lows out of 19 days have been below the long-term average.

We are now rapidly approaching the point in the year at which freezing temperatures have never been observed. This Sunday, with a record low of 33, is the earliest such date. On the high side, 95° seems to be some kind of cap for April. That reading has been reached on 4 different dates, including as early as the 17th, but never exceeded. chart from NWS data, photo © Kevin Ambrose

Tuesday, April 18, 2006

Not-too-taxing Weather (Unless You're a Plant)

Temperatures are at outstandingly pleasant seasonal levels in the Washington DC metro area this afternoon, mainly upper 60s by mid afternoon and a few 70s on the southern fringes of the region. As Matt indicated earlier, this fine spring weather is likely to continue for several more days.

Although heavier amounts fell to the south, the modest rainfall yesterday barely made a dent in the accumulated precipitation deficit. Dulles received only 0.25" vs. the 0.35" at National, and BWI had a mere 0.01". Here in the northern suburbs, about half the official amount fell at the local WeatherBug network station. chart from NWS data, photo © Kevin Ambrose

Tonight and Tomorrow

With clear skies and light winds, low temperatures tonight will be near 50 in the city, down to the lower 40s in the colder 'burbs. Tomorrow will look a lot like today, but a couple of degrees warmer, highs near 73.


Earth Day is approaching this Saturday, and PBS has climate change on the schedule for tonight. As PM Update previewed yesterday, NOVA is presenting "Dimming the Sun", based on a BBC program broadcast last year. Last night, posted a new entry noting that the NOVA version has been re-edited, hopefully to remove or put into better context some of the more extreme claims.

NOVA is immediately followed by "The State of the Planet's Wildlife", another program in the "Journey to Planet Earth" series. This program, narrated by Matt Damon, focuses on the effects of climate change on wildlife and the threat of widespread extinctions.

On Saturday, HBO is broadcasting the documentary "Too Hot Not to Handle", produced by Laurie David, wife of Larry David. All three shows are previewed in today's New York Times.

Monday, April 17, 2006

Today's Special: Dim Sun

Well, it worked! I took a cursory glance at radar and then watered the reseeded patch on the front lawn just before dinner last night. Sure enough, the first raindrops began within less than 2 hours. Showers were more numerous and intense south of the immediate Washington metro area overnight and this morning. By lunch time, radar was showing the northern edge of precipitation retreating south of the Beltway, although some showers near the mouth of the Potomac were moderate to heavy. At mid afternoon, sunshine was widespread here in MoCo north of the Beltway, but in southern portions of the region, clouds, drizzle and some light rain were persisting.

Surface weather and radar map at 2pm today from HPC/NCEP/NWS

Tonight and Tomorrow

Clouds should decrease throughout the area tonight with lows in the mid 40s in the District, lower 40s in the colder 'burbs. Tomorrow's highs will be in the mid 60s under scattered clouds.

Omnimedia: Something New Under the Sun?

PBS is broadcasting a new program in the NOVA science series, "Dimming the Sun", tomorrow night (8pm on WETA 26 in DC and WMPT 22 in MD, repeated Thursday at 1am, Friday at 2am and 4am on 26, Saturday at 10am on 22). The show is evidently based on a BBC Horizon program which aired in Britain about a year ago.

The theme of the presentation is that a reduction in the amount of solar radiation reaching the ground is actually reducing the observed effects of global warming. The appeal of this theory is that it can be used by both sides in the global warming policy debate. The supporters of action on global warming can say, "See, it's even worse than you think, because if it weren't for dimming, global warming would be even more intense." The opponents can say, "See, it's not a problem at all, because we can generate as much pollution as we want, and the greenhouse gas warming effects will be canceled out by the dimming."

Unfortunately for the ideologues, things in science are seldom as simple as the True Believers would like. At the time the original show was broadcast, the people at pointed out that too much certainty in the global warming debate can be just as dangerous as the attempt to create doubt by fake science sites. Whenever anyone boldly asserts, as the documentary does, that
Global dimming is a killer. It may have been behind the worst climatic disaster of recent times, responsible for famine and death on a biblical scale. And Global Dimming is poised to strike again.
it should raise a red flag.

Studies have shown that aerosols in the atmosphere, especially from volcanoes, can have a dramatic cooling effect on the atmosphere. Benjamin Franklin noted the largest lava eruption in historic time, in Iceland in 1783, as a likely cause of unusually cold weather in Europe. In 1815, Tambora volcano exploded in Indonesia. This was followed the next year by the notorious "year without a summer", in which New England observed frost in every month. RealClimate points out, however, that the claims for the current effects of global dimming simply do not match the observed data.

At a time when less than 20% of the public can be considered scientifically literate, it is important to beware of scientific arguments presented in excessively dramatic terms. By all means watch the program, but use your brain. RealClimate has posted two other analyses of the subject: "Global Dimming II" and "Global Dimming may have a brighter future"

Seasonal Outlook

Latest seasonal forecast: Click here.

Latest 3-month temperature outlook from Climate Prediction Center/NWS/NOAA.