Thursday, May 17, 2007

Back to the Sixties


Partly sunny, cool. Following yesterday's cold frontal passage, northerly breezes and some persistent clouds from a weak trough in the Ohio Valley have kept temperatures about 15° cooler this afternoon; most places are maxing out in the upper 60s.

Strengthening of the upper-level trough is likely to keep cooler temperatures and the possibility of showers in the area into at least part of the weekend.

Map of yesterday's rainfall from the NWS experimental precipitation analysis shows some amounts over half an inch (shades of green) mainly south of the District. Through much of Northern Virginia and the northern suburbs, however, amounts were below 0.25" (lighter shades of blue).

Tonight and Tomorrow

Mostly cloudy, cool, chance of showers. Low temperatures under mostly cloudy skies will be in the low to mid 50s tonight. Tomorrow will be mainly overcast with a 60% chance of showers, especially to the south and east of the metro area, and highs only 59-63°.

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

Climate Corner: Seeing the Forest or the Trees?

Thanks to an extensive cold spell in April, some people (including some professional meteorologists who should know better), have been implying that global warming is not a concern because "everything averages out." It's true that about 1200 daily low temperature records were set in the U.S. during the record cold outbreak of April 4-10. However, climate is not a subjective interpretation of extremes, and global climate is not determined only by what happens where most people (or even most meteorologists) live.

NOAA reported yesterday that, despite the extremes, April was near average for the U.S. overall. Globally, surface temperatures were the third warmest on record, and for the January-April period they were the warmest ever observed. Looking only at land locations, April temperatures were also the warmest on record. Nearly all of Europe averaged above average, with large portions of France, Switzerland, Germany, and Austria 9°F or more above average. Extensive warmth was also seen in Argentina and Brazil.

Wednesday, May 16, 2007

Showers, Storms, Some Severe?


** Severe Thunderstorm Watch in effect until 8 PM **

Showers and possible thunderstorms. Clouds increased this afternoon as showers and thunderstorms approached ahead of a cold front through the upper Ohio Valley. The rainfall promises a chance of at least some relief to areas running at least 50% below average for precipitation in the last 30 days.

Temperatures reached the low 80s in most places before the clouds moved in, with a high of 83° at both National and Dulles by 2pm. With the onset of rain, temperatures quickly dropped to the low 70s at Dulles. Following the frontal passage, much cooler temperatures will prevail for the next couple of days.

NWS experimental precipitation analysis shows most of the DC region at less than 50% of normal precipitation (orange) for the 30 days through this morning. Some areas, particularly in Northern Virginia, are less than 25% of normal (red).

Tonight and Tomorrow

Showers and thunderstorms ending, cooler. The heaviest activity has now moved east of the District, but some showers and isolated thunderstorms could still persist through 7-8pm, followed by some clearing by morning. Lows will be in the low to mid 50s. Tomorrow will be mostly sunny with lower humidity and highs 68-72°

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

Tropical Topics

Eastern Pacific hurricane season officially began yesterday.

Science Daily reported yesterday on some new research from NASA's Goddard Space Flight Center in Greenbelt on the role of air flow in a hurricane's eye for storm intensification. The results, which appear in the June issue of the American Meteorological Society's Journal of the Atmospheric Sciences, indicate that interaction between the eye and the eyewall, previously considered insignificant, plays a crucial role in the operation of the hurricane's heat engine.

Tuesday, May 15, 2007

Hot, Then Not
Showers and t'storms possible for tomorrow PM


Sunny, breezy, warm. A southerly breeze gusting over 25 mph at times has helped push temperatures well into the 80s in the Washington metro area this afternoon, at least 10° warmer than yesterday. This brings the first half of the month to about 2.5° above average. By mid afternoon, the hot spots in the region were Leesburg and Winchester, both at 88°. Dewpoints are still quite comfortable, mainly in the upper 50s. Regional radar is clear in all directions.

An approaching cold front will bring a chance of showers or thunderstorms late tomorrow and much cooler temperatures for Thursday. chart from NWS data, photo © Kevin Ambrose

Tonight and Tomorrow

Mainly clear, warm, then chance of showers and t'storms. Under mostly clear skies, lows tonight will be in the summery 60s: mid and upper in the city and lower in the 'burbs. Tomorrow morning will be mostly sunny, but clouds will increase in the afternoon, and there is a 50% chance of showers and possible thunderstorms by late afternoon or evening. The Storm Prediction Center has indicated a slight risk of severe weather. Highs will be 78-82°.

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

Climate Clues

NASA announced today that large areas of Antarctica, roughly the size of California, were observed to melt in January 2005. Melting was observed in multiple regions as far as 560 miles inland, within 310 miles of the South Pole, and at elevations above 6600 feet. Konrad Steffen, director of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado, Boulder, one of the leaders of the team of scientists, said
"Antarctica has shown little to no warming in the recent past with the exception of the Antarctic Peninsula, but now large regions are showing the first signs of the impacts of warming as interpreted by this satellite analysis. Increases in snowmelt, such as this in 2005, definitely could have an impact on larger scale melting of Antarctica's ice sheets if they were severe or sustained over time."

Law of Unintended Consequences

The rural electric coal subsidy story we linked to yesterday gets a more complete treatment on the bunny trail.

Monday, May 14, 2007

Maybe May, Maybe Not


Mostly sunny. The May temperature rollercoaster continues. After chilly lows of 49° at National and 40° at Dulles, temperatures have rebounded nicely to more nearly average May levels this afternoon, despite some high clouds drifting in from the northwest. Mid afternoon readings are mostly in the low 70s. Radar is generally dry; a small area of showers across the eastern WV panhandle has apparently dissipated. Westerly flow will bring in warmer air tomorrow from the Midwest, where readings were well into the 80s today, with upper 80s reaching as far north as central Minnesota.

Temperature chart at 4pm today from Unisys

Tonight and Tomorrow

Partly cloudy, becoming much warmer. Under partly cloudy skies, lows tonight will be in the mid to upper 50s in urban areas and lower 50s to near 50° in the cooler 'burbs. Tomorrow will be sunny and warmer with highs in the low to mid 80s.

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

Law of Unintended Consequences

The lead A1 article, "Federal Loans for Coal Plants Clash With Carbon Cuts", in today's WaPo describes how a Depression-era subsidy intended to bring electricity to rural areas is now subsidizing coal plants at the expense of CO2-reducing energy alternatives. By providing the additional energy needed for new ethanol production, these coal plants are even undermining the effectiveness of biofuels in reducing CO2 emissions.

Seasonal Outlook

Latest seasonal forecast: Click here.

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