Thursday, September 21, 2006

Summer Ending on a Crisp Note


Sunny, chilly. After morning lows of 50° at National and 43° at Dulles, temperatures have rebounded nicely, but they were still only in the upper 60s by mid afternoon. The Dulles low was only 1° above the record of 42° set in 1991. Today is the latest date in the year which has never seen a low below 40° there. Not only is the radar clear in all directions, but skies are virtually cloudless throughout the region south of the Mason-Dixon line.

Tonight and Tomorrow

Continued crisp. Lows tonight under clear skies will be chilly again, near 50° in the warmest urban areas to the low 40s in the coolest 'burbs. Get your excuses ready; tomorrow will be the perfect Friday for a "sick" day: Sunny, highs in the low 70s.

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

Pictured above: The map of surface pressure (solid lines) and 500 mb height (color shading) this morning from Unisys shows an unusually high amplitude pattern for late summer, with Helene moving around a high pressure area in the central Atlantic and our next weather maker, a strong low which brought substantial snow to portions of the central Rockies.

Tropical Topics

Hurricane Helene has turned north as expected well east of Bermuda, and a more easterly track is expected. Maximum winds are 80 mph.

The tropical wave west of the Cape Verde Islands hasn't become better organized yet, but gradual development is possible in the next couple of days as it continues moving westward.

Political Science

Today's NYT reports that, given the lack of action at the federal level, the state of California is suing the 6 largest auto makers over air pollution. The state Attorney General claims, "Global warming is causing significant harm to California's environment, economy, agriculture and public health." The suit is the first attempt to hold the companies liable for producing greenhouse gases. Articles on the lawsuit also appeared in the BoGlo (from the AP), LaTi, and UK Telegraph, among others. (Interestingly, the San Jose Mercury News has a story bylined from the WaPo, but a Google search of the online WaPo turns up only the AP and Reuters wire service reports.)

Wednesday, September 20, 2006

Feel of Fall


Breezy, cool. Northwesterly breezes gusting as high as 25 mph at times have brought a definite fall feel to the Washington DC metro area this afternoon. With the sun impeded by the clouds associated with the large upper-level trough which helped bring the cold front through the area yesterday, temperatures are having a hard time reaching 70°. The highest official hourly reading has been 69° at 2pm, after which scattered clouds gave way to a broken overcast and a temperature drop of 3°. The fall crispness is especially noticeable with the dewpoint readings in the low 40s, which are as much as 20° below the level of 24 hours ago. The composite radar image shows virtually no precipitation east of the Rockies, except for some showers enhanced by the eastern Great Lakes and some thunderstorms in southern Florida.

Tonight and Tomorrow

Cool. Winds will diminish somewhat after dark, but persistence of the cloud cover with the trough aloft will prevent low temperatures in many places from reaching the levels which could be implied from the low dewpoints. Lows should range from the low 50s downtown to the upper 40s outside the Beltway. Tomorrow will be partly cloudy, less windy, and cool with highs around 70°.

For the outlook through Friday and the weekend, scroll down to Dan's post below.

Tropical Topics

After giving a quick hit to the Azores, Tropical Storm Gordon has weakened, although it still maintained its tropical characteristics this morning; peak winds were 60 mph. It is becoming extratropical after a journey of almost 10 days through the Atlantic. Maximum winds are now 50 mph; the last tropical advisory was issued at 5pm.

Hurricane Helene weakened slightly to 105 mph this morning. The storm has begun a northward turn, moving northwest at 9 mph. It is still expected to remain east of longitude 60W. Its strength, large size, and persistence in the central Atlantic, however, have caused swells to increase along the East Coast.

Potentially the next tropical system is a large wave with strong showers and thunderstorms several hundred miles southwest of the Cape Verde Islands.

Tuesday, September 19, 2006

Falling Back to Autumn


Decreasing clouds, cooler. The official Washington temperature peaked at 80° just before a cold front passed through around 1pm today. Precipitation was extremely spotty, with only a trace at National and BWI, and nothing at Dulles. Despite a northwesterly breeze, cooler temperatures will be slow to filter into the area through the evening as clouds gradually decrease.

Tonight and Tomorrow

Cool, drier. Under clearing skies, low temperatures tonight will be near 60° downtown to the mid 50s in the cooler 'burbs with much lower humidity. Tomorrow will be sunny and dry with highs in the low 70s.

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

Tropical Topics

Hurricane Gordon is racing eastward at 33 mph with maximum winds of 85 mph toward the Azores, where a hurricane warning is in effect. The storm should have enough forward momentum to hit northern Portugal or Spain. If it retains its tropical characteristics in doing so, it would be only the second such tropical storm in history, after last year's Vince.

Helene remains a large hurricane with top winds of 115 mph this morning, down slightly to 110 mph at 5pm. It is currently moving west-northwest. Persistence on this track would take it toward the Bahamas and southern Florida, but the models are unanimous in steering the storm northward and then northeastward well east of longitude 60W.

Mediarology: She Blinded Me with Science

Somehow we don't think the audience will be tuning in for the science when The Weather Channel continues the rollout of its new show lineup. Abrams and Bettes: Beyond the Forecast, premiering next Monday night at 8, will be a one-hour Monday-Friday program covering "topical weather stories by going behind-the-scenes of high-profile weather events live and on-location, in an off-the-cuff irreverent style." Co-host Stephanie Abrams and her "breezy style" were recently profiled in the Palm Beach Post. For an even more "breezy and irreverent" take on the subject, see

The following Sunday, October 1, is the premiere of The Climate Code, which was previewed recently in PM Update.

Photo of Stephanie Abrams from Palm Beach Post

Monday, September 18, 2006

Summery Summary


Summery. After nearly a week in which temperatures barely made it into the 70s, the Washington metro area has been enjoying much more summer-like conditions since yesterday. Yesterday's official high of 81° was matched by 2pm today, and readings around the region are mostly in the mid 80s. There is no rain east of the mountains, but a vigorous cold front pushing eastward from the Ohio Valley is bringing showers and thunderstorms from southern Canada all the way to the Gulf States.

Tonight and Tomorrow

Increasing clouds, chance of showers. Clouds will increase overnight toward morning with lows in the mid to upper 60s. Tomorrow will be mostly cloudy with a 50% chance of showers or thunderstorms in the afternoon and highs from 75° to 78°

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

Tropical Topics

Helene strengthened this morning to 125 mph (strong Category 3) based on satellite observations but was lowered to 115 mph in the 5pm advisory after a NOAA research plane made some measurements. After moving north-northwestward for a while, it is now turning more westward. A continued westerly track could have the potential to threaten land, but Dr. Jeff Masters points out in his blog that of the 16 hurricanes in history which have passed within 300 miles of Helene's position, the only one to make landfall in the U.S. was Isabel (2003). Furthermore, Isabel started out more southerly than Helene. None of the latest models brings the storm even as far as longitude 60W (about the eastern tip of Nova Scotia). The official forecast track, which had been further west than any of the models, has now been shifted east of 60W.

Gordon has intensified to 90 mph as it continues moving eastward in the open Atlantic toward the Azores. A tropical storm watch is now in effect for the Azores.

Historical hurricane track map from

Climate Corner

Dr. Barrie Pittock's talk at Busboys and Poets is tomorrow evening. Details are in Friday's PM Update.

Seasonal Outlook

Latest seasonal forecast: Click here.

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