Where Are the May Showers?

Southwesterly flow ahead of a cold front in the Ohio Valley is sending balmy temperatures all the way up the Atlantic Coast into northern New England this afternoon. Locally, temperatures reached typical early June levels with readings of 80° or above by 3pm at all Washington DC metro area locations except for river-breezed Quantico.

As Josh explained earlier, needed precipitation will be quite scarce over the next several days; this morning's GFS model has the DC area on the northern edge of minimal precipitation at best for at least the next 48 hours. The afternoon NAM model is only a little less stingy; it comes up with less than 0.10" through Saturday.

Temperature chart at 3pm today from Unisys

Tonight and Tomorrow

Under mainly cloudy skies later tonight, low temperatures will have a hard time breaking below 60 in the District and mid 50s in the 'burbs. Friday will feature considerable cloudiness for much of the day but only a 30% chance of showers. Highs should be able to reach the mid 70s, closer to 80 if there is more afternoon sun.

April Showers Drying Up

Mid April's rain took a bite out of the 2006 precipitation deficit, but we're likely to be once again over 30% below average in the next few days. April showers are supposed to bring May flowers, but in the most recent 30-year climatological reference period, April is the driest month in Washington, with an average of only 2.77" vs. 3.82" for May. (February is lower in absolute terms, but of course it has 2 fewer days, on average.) The daily average increases over 50% from a low of 0.08" on April 15 to 0.13" by May 12. So far this year, we're going directly against that trend.

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

D.C.'s Dryness Continues

Some scattered showers in the region this morning fell apart before reaching the Washington metro area, although Hagerstown did manage to squeeze out a trace of rain, and Charlottesville had 0.01". The persistent clouds kept temperatures from rebounding quickly above the summer-like overnight lows in the low 60s, but more sunshine later pushed most readings into the mid 70s by mid afternoon.

Tonight and Tomorrow

Broken clouds this evening will give way to clearing skies by morning, with lows in the mid 50s in the city and upper 40s in the colder 'burbs. Tomorrow will be sunny and dry with highs around 79.

"Another Nail in the Coffin"

Today's WaPo has an article, "Study Reconciles Data in Measuring Climate Change", which describes a government report resolving the previously reported discrepancies between surface temperature measurements and those reported by satellites. This is described as "really a major step forward" and "the nail in the coffin of [the skeptics'] argument" against global warming. Courtesy of MIT's Knight Science Journalism Tracker, here are some more links to the study report:

• New York Times: Federal Study Finds Accord on Warming
  
• Associated Press: Global Warming Differences Resolved
  
• NOAA Press Release: Report Reconciles Atmospheric Temperature Trends

The entire report is available for download in PDF format. The usual suspects don't seem to have found a way to attack the report yet, but they will undoubtedly come up with something.

Squeeze Play Sends Fine Weather Into Extra Innings

An atmospheric squeeze play is extending the fine spring weather from April into May in the Washington DC metro area. A ridge of high pressure extending along the entire east coast of North America is being squeezed from two directions by "cut off" low pressure areas over the upper Midwest and near Bermuda. While the ridge holds in place, the sunny, dry weather will continue over the Mid Atlantic area as Jason describes below, but the unusual northwestward motion of the eastern low will bring the threat of some clouds and rain to New England.

Surface pressure (solid lines) and 500 mb height (colors) at 8am today from Unisys

At mid afternoon today, 68° was the lowest reported reading around the region; most places were 70° or higher. The bright sun was accompanied by delightfully dry dewpoints of 45° or less. The nearest showers were over the lower Ohio Valley and eastern New England.

Tonight and Tomorrow

Mostly clear skies should continue through tomorrow afternoon, with only a few clouds late in the day. Lows tonight under light winds should again be in the mid to upper 40s city to near 40 in the colder 'burbs. Highs tomorrow will be near 72.

Capitol Climate

The American Meteorological Society has posted more details on the next Capitol Hill Environmental Science Seminar this week:

• Topic: Changes in Cold Places: A Look at the Greenland Ice Sheet, Arctic Sea Ice and the Antarctic Ice Sheet
  
• Date: Wednesday, May 3, 2006
  
• Time: 12:00 Noon - 2:00 pm
  
• Location: Russell Senate Office Building, Room 428

The public is invited; no pre-registration required.

The questions to be addressed are:

Are parts or all of the Greenland and Antarctic Ice Sheets undergoing a net melting? What is the nature of the observational evidence of melting? How far back in time do these observations extend? Are the melting and rates of melting consistent with model simulations and projections of melting? What are the factors deemed responsible for the melting? Is Arctic Sea Ice thinning? If so, by how much and over what period of time? What is the nature of the observational evidence for this thinning? Are the thinning and rates of thinning consistent with model simulations and projections of thinning? What factors are deemed responsible for the thinning of Arctic Sea Ice? Are there implications with respect to sea level rise? Is there any evidence of a fundamental change in the rate at which the Greenland ice sheet is changing and the manifestation of those changes? If so, why? How well do model simulations capture the dynamics of ice sheets and sea ice relative to observations? How well are these ice sheet models poised to project future changes in ice sheets, sea ice and sea level?

Photo, via AMS, is also the cover picture for the April 2006 Weather Magazine of the Royal Meteorological Society (Special Issue: Climate Change in high latitudes 2). It shows surface melt water entering a moulin in the Greenland Ice Sheet.