Friday, March 24, 2006

Wind-ing Down

At least there's no wind with the chill. Late March sun through a high overcast in the Washington DC metro area is pushing temperatures this afternoon a degree or 2 higher than yesterday's below-average high of 51. Clouds and a chance of showers are likely through much of the weekend as weak disturbances rotate southeastward around a persistent upper-level low now centered over the Great Lakes. Meanwhile, a surface low lurking off the Carolina coast is modeled to deepen vigorously by Sunday afternoon. As it remains well off the coast, however, its effects on the local area are expected to be limited to reinforcing the flow of cold air with its counterclockwise circulation.

North American 500 mb height (colors) and surface pressure (solid lines) this morning from Unisys

Tonight and Tomorrow

Under cloudy skies tonight, lows will range from near 40 city to upper 30s 'burbs. Clouds will continue tomorrow with highs in the upper 40s, a couple of degrees warmer if more sun breaks through. There is a 30% chance of light showers tonight, 50% tomorrow.

March Winds

The month so far has lived up to March's reputation as the windiest month, but the overall average of 11.5 mph is only slightly higher than the long-term average of 11.1. The peak gust of 45 mph on the 15th is less than the 52 mph recorded in 2002. The maximum 2-minute wind of 36 mph (not shown) was also exceeded in 2002.

CapitalClimate chart from NWS data, photo © Kevin Ambrose

Thursday, March 23, 2006

Happy WMD!

Have you thanked a meteorologist today? It's World Meteorological Day, the anniversary of the founding of the World Meteorological Organization in 1950. This year's theme is "Preventing and Mitigating Natural Hazards". The WMO Secretary-General's message notes that 90% of natural disasters involve weather, climate and water. During the 10 years ending in 2001, natural disasters were linked to 622,000 deaths worldwide; the damage from hydrometeorological disasters was estimated at $446 billion.

Chilly but dry conditions continue across the metro Washington DC region this afternoon with temperatures near or a little above 50. The near-term outlook is well covered in Josh's earlier post, so let's take a longer-range view (about 130,000 years).

Hot off the Press Release

Earlier this afternoon, the National Center for Atmospheric Research (NCAR) in Boulder announced the publication of 2 papers by NCAR scientist Bette Otto-Bliesner and University of Arizona Environmental Studies Laboratory Director Jonathan Overpeck in tomorrow's issue of the journal Science. While not a smoking gun, the new studies help build a picture of the potentially catastrophic consequences of global warming. Combining paleoclimate records (such as ancient coral reefs and ice cores) with output from the NCAR Community Climate System Model (CCSM), the researchers found that a 5-8° F warming of Arctic temperatures by the end of this century from increased greenhouse gases would produce conditions as warm as those of 130,000 years ago. That was the period between the last great ice age and the previous one, when sea level was 20 feet (6 meters) higher than today. This is a much faster rate of sea-level rise than has previously been assumed.

The notion of abrupt climate change was unfortunately distorted out of all recognition by the recent movie, "The Day After Tomorrow", but it has been receiving much more serious attention in the last decade. The graph, from a National Academy of Sciences report, "Abrupt Climate Change", shows a very rapid warming from the so-called "Younger Dryas" period about 12,000 years ago. At that time, the temperature increased by 8° C in only a decade.

Dr. Overpeck presented an excellent overview of the abrupt climate change theory in a lecture at the American Geophysical Union (AGU) annual meeting in 2002. For some other intriguing speculation on modes of climate shift, check out the Charney lecture by MIT Prof. Kerry Emanuel (of hurricane intensity fame) from 2001. The AGU lecture archives, which I just discovered yesterday, are a treasure trove of interesting material from AGU meetings back to 1999. The two which I have sampled so far should be quite accessible to a general audience.

Tuesday, March 21, 2006

Spring of Our Discontent

After such an underachieving winter, what was already featured as a low-potential system created some excitement among the snow-lovers as it approached the Washington DC metro area today. Unfortunately for the flake fanatics, the extreme dryness at the surface won out over all of the other factors. Actually, no matter where you were in the metro area, you were probably no more than a mile or so from some moderate snow. The only catch is that it was straight up, and most of it evaporated before reaching ground level.

Around noon, radar truthfully showed snow falling nearly everywhere within about a 30-mile radius of the Washington Monument. The radar image above from shows snow across most of the area around noon. The surface map to the right from College of DuPage around the same time shows light snow falling in Washington, but a large area of 20° and lower dewpoints from the Mid-Atlantic region across the Northeast and back into the Great Lakes. After 2 hours of light snow, National was able to eke out 0.01" of precipitation at temperatures of 33-34°.

Remember, we told you yesterday that the devil was in the details. Ultimately, the models were just a little bit too strong on the moisture. Having said that, the models are still hinting at a little more light snow or flurries tonight, especially in the mountains, as the upper-level energy now over the Midwest and Ohio Valley moves eastward and out to sea.

The big story here is the fact that we have now had only about 1% of average precipitation in the last month and only about 10% in the last 6 weeks, with a mere 0.04" so far in March. If we don't get some soon, we will be looking at serious drought conditions going into the warmer part of the year.

Tonight and Tomorrow

For tonight, there is a slight chance of some light snow showers or flurries. Clouds will decrease toward morning with lows near 29. Tomorrow will be sunny with highs in the upper 40s.

Tropical Topics

With a little over 10 weeks before the official start, it's not too soon to start thinking about hurricane season. The Southern Hemisphere season is in full swing now. The AP graphic via BBC shows Cyclone Larry, a Category 5 storm, slamming ashore in Northern Queensland, Australia on Monday, local time. Fortunately, there were no reported deaths despite the severe damage from winds up to 180 mph. A second storm, Cyclone Wati, is now approaching the coast as a Category 3. It is forecast to intensify but remain offshore.

Closer to home, AccuWeather is going for the hype by touting the likelihood of a hit on the East Coast. In his typical low-key style, Joe Bastardi is quoted saying, "The Northeast is staring down the barrel of a gun."

PM Update will be taking off tomorrow to work on a global warming story so hot it is embargoed for release until 2pm on Thursday.

Seasonal Outlook

Latest seasonal forecast: Click here.

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