Thursday, August 9, 2007

Relief On the Way, But With an Asterisk


Hot, humid, scattered thunderstorms. Relief is arriving for the Washington area's record-breaking heat, but it comes with an asterisk; the temperature drop is likely to be short-lived, and there is little prospect for serious improvement in the deepening drought conditions.

A large complex of thunderstorms extending from north of Harrisburg through the Baltimore metro area to the northern DC suburbs early this afternoon helped reduce temperatures, but precipitation was mainly limited to north of the Beltway. BWI received almost half an inch (0.43") , but National got a mere 0.02" and Dulles had only a trace with some thunder . Despite the fierce appearance of the storms on radar, damage reports were relatively sparse. Temperatures were well into the 90s by 1pm, but they retreated to the 70s in areas with rain, where they have now rebounded to the low and mid 80s.

Another area of storms now in southwestern Pennsylvania is likely to take a similar track toward the northern portions of the region in the next couple of hours.

Tonight and Tomorrow

Hot, humid, scattered thunderstorms possible. There is still a 40% chance of thunderstorms through this evening, especially in northern areas. Lows will be in the upper 70s in the city to the mid 70s in the 'burbs with uncomfortable humidity. Tomorrow will be hot and humid with highs 90-95° and a 30% chance of showers or thunderstorms.

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

Tropical Topics

The Climate Prediction Center and National Hurricane Center today released an updated hurricane season outlook. It continues to call for an above-normal season, with an 85% chance of greater than average tropical cyclone activity. The forecast includes a range of 13-16 named storms, 7-9 hurricanes, and 3-5 major hurricanes.

Climate Corner

The August issue of Scientific American has an excellent non-technical article on "The Physical Science behind Climate Change". The authors were all members of Working Group I of the 2007 IPCC assessment. Besides reviewing the scientific evidence for global warming, the article also discusses the remaining uncertainties. The key concepts are summarized by the editors in the box to the right.

Humor Dept.: "There Once Was Some Wind Off Nantucket . . . "

The Daily Show's "Jason Jones 180" recently produced a hard-hitting investigation of Big Wind's shameless attempt to exploit the hapless natives of Nantucket.

Wednesday, August 8, 2007

Swinging for the Record Books: Heat on Steroids

**Heat Advisory in Effect Until 8 PM This Evening **


Sunny, record heat, humid. Unhindered by the clouds of yesterday and helped by a drying westerly breeze, the sun went to bat today chasing a long-standing temperature record. The temperature rose several degrees an hour through the morning, as much as 5° between 9 and 10 am, and by 1:03, the National Airport temperature hit 102°, breaking the record for the date set in 1930. After retreating several degrees temporarily, the temperature was back up to 101° at 4pm. Except for the 97° at 2pm, the reading at National has been at or above 100° for 5 consecutive hours.

Records were also set at both of the other major airports: at least 100° at Dulles and 102° at BWI. Several records were set or tied elsewhere in Virginia as well: Richmond 102°, Danville 100° (tied), Blacksburg 91° (tied).

Humidity is also quite high, although the 8 hours of greater than 75° dewpoints overnight were replaced by readings near or below 70° this afternoon. When combined with the hot temperatures, however, the heat index reached at least 108°. Scattered locally severe thunderstorms fired up in the early afternoon between Pittsburgh and Morgantown WV, but these have so far remained over and west of the mountains. chart from NWS data, photo © Kevin Ambrose

Tonight and Tomorrow

Hot, humid, scattered thunderstorms possible. Very warm and humid conditions will continue overnight with only a slight chance of scattered thunderstorms through this evening. Lows will be mainly in the upper 70s to near 80° in town and some mid 70s in the 'burbosphere. Tomorrow will be mostly sunny and not quite as hot with highs 93-97° and only a 20% chance of afternoon or evening thunderstorms.

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

Climate Corner

While today's WaPo featured the current heat wave on the front page, inside the A section was an article, "Across Globe, Extremes of Heat and Rain", about a just-released World Meteorological Organization report on recent extreme weather events throughout the globe. Although any individual weather event cannot be directly tied to climate change, widespread extremes are certainly consistent with such a scenario.

Also on today's WaPo front page was an article, "Warming Draws Evangelicals Into Environmentalist Fold", about the developing collaboration between evangelical groups and the environmental movement.

Tuesday, August 7, 2007

High Summer

**Heat Advisory in Effect Until 8 PM This Evening, 1 PM to 8 PM Wednesday **


Hazy, hot, humid. High summer had many residents of the Washington metro area feeling "down, low down" today, but the most hyped extremes of heat failed to materialize as the core of the heat wave remained to the south and west of the region. At mid afternoon, Culpeper had the lone triple-digit temperature, but the 104° heat index there was exceeded by the 109° reading at Fredericksburg resulting from a 97° temperature/75° dewpoint.

In the immediate vicinity of the Beltway, temperatures at post time are generally in the mid 90s. Thunderstorms on radar are mainly limited to Pennsylvania, although a scattered and weakening line extends through eastern West Virginia.

Very hot temperatures and uncomfortable humidity will continue through at least tomorrow, with one major model predicting a high of 103°.

Tonight and Tomorrow

Hot, humid, scattered thunderstorms possible. There is a very slight chance of an isolated thunderstorm through this evening; otherwise, it will be another warm and sticky night with lows dipping into the upper 70s downtown and the lower 70s in the 'burbs. Tomorrow will be continued hot and humid with highs 96-101° and heat indices as high as 105-107°. There is only a slight chance of an afternoon or evening thunderstorm.

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

Tropical Topics

Although several typhoons have been active in the Pacific recently, the tropical Atlantic remains quiet.

The Miami Herald and the Palm Beach Post both reported today on the news we posted yesterday regarding the suggestion that ousted National Hurricane Center Director Proenza return to his old job in Texas.

Mediaorology: "Sultry 24/7"

Yesterday's New York Daily News TV section featured a review of The Weather Channel's female talent (Alexandra Steele, Heather Tesch, Stephanie Abrams, Nicole Mitchell).

Alexandra Steele photo from The Weather Channel

Monday, August 6, 2007

DC: Dewpoints Climbing

** Heat Advisory in effect noon to 8pm Tuesday **


Hazy, hot, humid. Yesterday's showers varied widely in amount across the region, from zero in parts of Northern Virginia to over an inch in some eastern locations. (The green areas through much of Prince George's County range from 0.5" to as high as 1.5", while the blues through much of the District and Montgomery County are less than 0.5", and most of Fairfax County is less than 0.1".)

The additional moisture, however, has helped lift dewpoints into the sultry low 70s, a level which pushes the heat index up about 7 or 8 degrees from the temperatures in the low 90s. Both Ft. Belvoir and Manassas were sporting heat indices of 100° by 2pm, and Ft. Belvoir was the hot spot at 4pm with an index of 103°. By mid afternoon, however, radar showed only a few isolated showers, mostly southward along I-95.

Hot temperatures and uncomfortable humidity are likely to continue through the middle of the week.

Chart of 24-hr. precipitation through 8am this morning from NWS Southern Region.

Tonight and Tomorrow

Hot, humid, scattered thunderstorms possible. There is still a slight chance of an isolated thunderstorm through this evening; otherwise, it will be a warm and sticky night with lows barely getting into the upper 70s downtown and the lower 70s in the 'burbs. Tomorrow will be continued hot and humid with highs 95-99° and heat indices approaching 105°. There is only a slight chance of an afternoon or evening thunderstorm.

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

Tropical Topics

The tropical wave which tracked westward through the Caribbean late last week has pushed onward into Central America without developing.

As the Proenza affair at the National Hurricane Center continues to unfold, the House Committee on Science and Technology announced today that the chairmen of 2 subcommittees have sent a letter to NOAA Administrator Lautenbacher requesting that Proenza be returned as Director of the NWS Southern Region if he is permanently removed from his post at the NHC. According to the letter, NOAA had planned to assign Proenza as training chief of the Office of Climate, Water and Weather Services, a "drastic demotion", before the NHC assessment team had even been formed. An article in Friday's Miami Herald reviews Proenza's campaign to get his job back.

The paper by Holland and Webster on "Heightened Tropical Cyclone Activity in the North Atlantic" which PM Update posted on last Monday has been referenced in the Science Notebook of today's WaPo, but without the crucial caveat that this issue is far from settled because of the limitations of the available data.

Seasonal Outlook

Latest seasonal forecast: Click here.

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