Thursday, October 11, 2007

Hot and Humid to Cool and Crisp


Variable cloudiness, much cooler. Today's WaPo front page and garden section point out that the 27th consecutive day without measurable precipitation may not be good for water supplies, but abundant sunshine should be helpful for the kickoff tomorrow of the Solar Decathlon on the Mall. Go Terps and 'Tute!

After some popup showers, mainly to the north, accompanying a second cold frontal passage last night, northwesterly winds gusting as high as 25 mph at times have helped keep temperatures generally in the mid 60s this afternoon. After reaching 66° earlier (the same as yesterday's low), National was back down to 63° at 4pm; Dulles and BWI were 62°. The air is also quite dry; dewpoints are as low as the mid 30s. chart from NWS data, photo © Kevin Ambrose

Tonight and Tomorrow

Partly cloudy, cool. Under decreasing clouds, lows tonight will be in the upper 40s to near 50° in the city and the mid 40s in the 'burbs. Tomorrow will be mostly sunny and breezy with highs 65-68°.

For the outlook through the weekend and beyond with Larson's Long-Range, scroll on down to Josh's post below.

El Niño Update

The latest El Niño/Southern Oscillation Discussion, released today, indicates that "La Niña will likely continue into early 2008." La Niña conditions strengthened last month in all of the Niño regions with negative sea surface temperatures expanding westward in the equatorial Pacific. Expected impacts of a weak-to-moderate La Niña in the next several months include above average precipitation in the Pacific Northwest and continued below average precipitation in the Southwest. The next update is scheduled for November 8.


Bob Ryan, a former President of the American Meteorological Society, is the co-author of an important guest editorial in the August Bulletin of the AMS on the subject of climate change and the public. It says, in part,
Increasing numbers of broadcast meteorologists, to whom the public looks for information and guidance on climate change and global warming, are not offering scientific information but rather, all too often, nonscientific personal opinions . . . We strongly believe that, above all, if we are to professionally, fairly, and objectively communicate scientific information (as opposed to a personal or political opinion), we should use our scientific training to stay as informed as possible . . .

Wednesday, October 10, 2007

DC Hits the Drifecta


Sunny, cooler, less humid. A few spots in the region, especially well to the north and east of the Beltway (NWS map out for maintenance) got some welcome showers last evening, but all 3 major airports saw only a trace, and National is now approaching the end of its fourth consecutive week without measurable precipitation. At this point, it would take at least 2" of rain the rest of the month to keep this September-October from being one of the top 10 driest such periods in 137 years of records. The driest, shown in the chart, was 1930 with 1.04"; this year's total so far is 0.60".

After yesterday's trifecta of temperature records and high humidity, the cooler temperatures and much drier dewpoints are a relief, but temperatures are still a good 10° or more above seasonal averages. By mid afternoon, most locations were in the low 80s, while dewpoints had dropped into the very comfy upper 40s. A reinforcing shot of cool air will accelerate the downward temperature trend tomorrow. chart from NWS data, photo © Kevin Ambrose

Tonight and Tomorrow

Mostly clear, then some clouds and much cooler. Lows tonight under clear skies will range from the upper 50s downtown to the low 50s in the 'burbosphere. Tomorrow will be much more Octobery: partly to mostly sunny and breezy with highs 65-69°. There is a slight chance of a passing shower in the afternoon.

For the outlook through the rest of the week and into the weekend, scroll on down to Jason's post below.


The second episode of the new PBS Wired Science series tonight is scheduled to feature a segment on the effect of global warming on gardening and also on where rubber duckies go to die. Showtime is 8pm on WETA 26 and WMPT 22 (your cable system may vary).

Planetary Weather

The NYTi reports today that NASA's New Horizons spacecraft, while getting a slingshot boost by Jupiter earlier this year on its way to Pluto, discovered lightning in Jupiter's atmosphere at both poles, the first time this has been observed beyond Earth. The spacecraft was designed and built, and is operated by, the Johns Hopkins University Applied Physics Lab in Laurel.

Tuesday, October 9, 2007

Historic Heat Halting


Mostly sunny, record heat, humid. The Mid Atlantic region's historic October heat wave is being squeezed out from both the northeast and the west this afternoon, but not before new daily records were set at all 3 major airports. By 4pm, all local reporting locations had reached 90° or above. Although dewpoints are a little lower than yesterday, the humidity is still noticeable.

Unlike many recent days, regional radar shows some activity east of the mountains, but at mid afternoon it was limited to the Eastern Shore west of Ocean City, near the heads of the Chesapeake and Delaware Bays, and over the Blue Ridge south of I-66. At post time, a more extensive line of storms extends from central Pennsylvania southwestward across extreme western Maryland and into West Virginia.

Temperature chart at 3pm today from Unisys

Tonight and Tomorrow

Very warm, humid, chance of showers, then cooler. Warm and humid conditions will last through this evening with a 30% chance of showers or thunderstorms. Cooler and drier air will arrive by morning with lows in the low to mid 60s and some upper 50s to the west. Any remaining clouds tomorrow morning will give way to a mostly sunny day with decreasing humidity and highs 79-83°.

For the outlook through the rest of the week and into the weekend, scroll on down to Dan's post below.

Tropical Topics

The area of interest in the western Caribbean has not become any more organized today, and the tentatively scheduled reconnaissance flight was canceled.

Political Science

Chairman Edward J. Markey of the Select Committee on Energy Independence and Global Warming issued a statement in reaction to Sunday's WaPo op-ed piece by Bjorn Lomborg (see yesterday's update). For more background on Lomborg, see "Bjorn Lomborg feels a chill" (log in or watch the Visa ad) and a special edition of Grist Magazine at the time of his first book's publication. SourceWatch also provides an abundance of additional history and links. SciAm did an extensive critique by four specialists in 2002.

Monday, October 8, 2007

DC: Dehydration City


Mostly sunny, hot, humid. Weather news hasn't taken a holiday for Columbus Day. The record heat was a factor in yesterday's Army Ten-Miler, although not as major as in Chicago, where the Marathon was shut down early.

In a repetition of a familiar pattern recently, however, this morning's haze and mist kept the noon temperature over 10° below yesterday's. On the other hand, by 4pm the 91° at Dulles had broken the record there by 6°, and several other regional reporting locations, including downtown Baltimore at 92°, had reached or exceeded 90° again. National had at least tied the record with 88°. At this point, we are only 3 days from the latest 90° ever recorded in Washington, on the 11th in 1919.

Tonight and Tomorrow

Very warm, humid. Tonight will again be warm and humid with lows in the upper 60s downtown to the low 60s in the 'burbs. Some morning clouds and fog will give way to mainly sunny skies in the afternoon tomorrow with highs near record levels at 86-91°. There is a very slight (20%) chance of afternoon showers or thunderstorms.

For the outlook through the rest of the week and into the weekend, scroll on down to Dan's post below.

Tropical Topics

The National Hurricane Center is watching an area of storminess in the northwestern Caribbean, but a reconnaissance flight was canceled today and tentatively rescheduled for tomorrow.

The WaPo science three-quarter page today features the experimental Aerosonde technology for investigating the lowest levels of a tropical storm more safely and more economically than by manned aircraft.

Image © Aerosonde Pty Ltd

Political Science

Yesterday's WaPo Outlook section gave the entire front page above-the-fold space to an op-ed by Bjorn Lomborg, "Chill Out", on the subject of climate change policy. "Who is Bjorn Lomborg?": The misinformation watchdog group Media Matters addressed this question when Lomborg was featured in the WaPo last spring. The scientific accuracy of Lomborg's recent book, "Cool It", was discussed in a WaPo review last month. For more analysis of Lomborg's credibility, including the filing of formal scientific dishonesty charges, see the critiques of climate scientists and a Danish biologist. Many of the (as of last count, 176) online comments to the piece are quite instructive, as well.

Seasonal Outlook

Latest seasonal forecast: Click here.

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