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.

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 CapitalWeather.com 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.


CapitalWeather.com chart from NWS data, photo © Kevin Ambrose

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.

CapitalWeather.com 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.

See CC TV

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, RealClimate.org 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.

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 RealClimate.org 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"

Drought Eggstended Another Day

Today's weather is a good lesson in insolation. No, not the stuff you put in your attic. Thanks to the inclination of the Earth's axis, the incoming solar radiation today, 24 days after the Equinox, is roughly the same as it was on August 28. (So don't forget the sunscreen, boys and girls!) With the persistent cloud cover over the region, however, temperatures have been slow to climb, even with a brisk southwesterly wind gusting over 20 mph. On the other hand, by mid afternoon, breaks in the clouds were allowing temperatures to reach the mid 70s.

Sprinkles associated with the clouds were mighty few and far between. Among the major local airports, BWI was the winner of the rainfall derby by far, with 0.01" eclipsing the trace at Dulles and zero at National. At mid afternoon, radar showed a band of showers from southeastern Pennsylvania to just north of Baltimore and another area southwestward from Charlottesville. Although some more showers could pop up through this evening, mainly dry conditions will prevail in the metro area.

To the west, temperatures soared under high pressure through the central part of the country. The Weather Channel reported that over 40 temperature records were set in the Midwest yesterday.

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

Tonight and Tomorrow

Temperatures tonight will have a hard time getting below 60 in the city under broken clouds while the 'burbs should see temps in the mid to upper 50s. Tomorrow, fewer clouds in the afternoon should have June-like conditions busting out all over with highs around 80, although there is a chance of showers, at least in the morning and possibly again late in the afternoon.

Smithsonian Plays it Cool

Two new exhibits on climate change open at the Smithsonian Natural History Museum today. They were previewed by Joel Achenbach ("Hot Air and Glacial Change: A Case Study") with his inimitable style in the WaPo on Wednesday. (CAUTION: Achenbach's columns contain over 100% of the Recommended Daily Allowance of irony; they have been known to generate severe knee-jerk reactions.) Achenbach concludes, "It's all rather low-key." It's so low-key that the exhibits didn't even appear on the museum web site until the last day or two. The exhibits are: "Arctic: A Friend Acting Strangely" and "Change is in the Air". They are both scheduled to run through November.

Picture of the atmosphere from space by NASA, via Smithsonian National Museum of Natural History

It Ain't Over Til Momma Nature Says it's Over

Just when you thought the hurricane season of 2005 had gone into the history books with a record 27 storms, the National Hurricane Center has announced that reanalysis shows a low near the Azores on October 4-5 was an unnamed subtropical storm, making a total of 28 storms for the season. There are 48 days until the official start of this year's hurricane season.

DC: Deficit Capital

A very weak frontal boundary moving through early this afternoon touched off some thunderstorms in the southern portion of the Washington DC region. Moving southeastward from Fauquier and Prince William Counties in Virginia, the storms crossed the Potomac into Charles County, where they prompted a severe thunderstorm warning, which was cancelled shortly after 3pm. Site visitor PC reported nickel-sized hail in eastern Prince William.

At post time, radar showed some scattered light activity south of the District, but the earlier area had intensified over the lower Chesapeake Bay, just south of the mouth of the Potomac. For the rest of the afternoon and evening, a few more isolated storms could pop up, but conditions will be mainly dry. See Josh's post below for the chances of receiving some much-needed rain over the weekend.

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

Tonight and Tomorrow

Lows tonight will remain quite mild for the season, mid to upper 50s, under partly cloudy skies. Today's models are showing an unusually wide range of temperatures for tomorrow, but a consensus target somewhere in the mid 70s looks reasonable, with sun through broken to overcast skies. The chance of showers, especially in the afternoon, is 40%.

Deficits Matter

The Nation's Capital has been the home of "Red Ink Run Amok" for quite some time, but it is also recently experiencing a deepening precipitation deficit. The chart shows the accumulated precipitation this year as a percentage surplus or deficit relative to the long-term average. Following a January which was almost exactly "normal", early February was quite wet, but the surplus was more than wiped out by the record-breaking dry March, and the rain so far in April has barely maintained the status-quo. Although a holiday weekend is coming up, that sound you hear is from the lawns and shrubs throughout the region crying out for more moisture.

CapitalWeather.com chart from NWS data, photo © Kevin Ambrose

A Beautiful Day in the Neighborhood

"It's a beautiful day in this neighborhood", with even the Anomalous Airport reaching 70° by early afternoon. Many other locations in the Washington DC metro area were in the mid or upper 70s at mid afternoon. Here at Afternoon Blog Central, it's up to an unofficial 78&deg.

It's also still very dry, although not as much as Ft. Belvoir's continuing bogus 11% relative humidity. My first lawn mowing of the season today was probably as late as any in the last 16 seasons at this address. That's probably due to the record-breaking dryness of March, since temperatures have not been particularly cold. Thanks to the rain last week and over the weekend, we're still about a third of an inch above normal for April, but that excess is likely to be dissipated within the next couple of days.

Tonight and Tomorrow

Tonight will be mostly clear with lows around 50. Tomorrow, clouds will increase, especially in the afternoon, with highs in the low 70s.

Space Weather

In the nearby Solar System neighborhood, the European Space Agency Venus Express mission was successfully inserted early this morning into orbit around Earth's evil twin. Venus' atmosphere is an example of the greenhouse effect on steroids. The nearly 100% CO2 atmosphere has about 90 times the density of our own atmosphere. This results in a surface temperature of about 470° C, even higher than the surface of Mercury and hot enough to melt lead. Unlike an earlier mission whose main purpose was to map the surface of the planet, Venus Express is designed to study the atmosphere. For some interesting background information, see the latest post at RealClimate.org.

Graphic from European Space Agency