Friday, January 12, 2007



Showers, cool. Persistent light showers ahead of a very strong Arctic front from the Great Lakes to central Texas have put a damper on temperatures in the Washington metro area, keeping them below yesterday's optimistic projections. They were still mild enough to break the string of 2 consecutive 1°-below-average days, however. Highs were 49° at National, 47° at Dulles, and 50° at BWI.

Total precipitation so far has been only a few hundredths of an inch at each location. Increasing moisture on southwesterly flow ahead of the approaching front is likely to put a damper on most of the holiday weekend as well.

Temperature chart at 3pm today from Unisys

Tonight and Tomorrow

Chance of showers, cool. There is a 30% chance of showers overnight with lows in the low to mid 40s. Tomorrow will be cloudy with a 50% chance of light showers and highs in the upper 50s.

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

Canadian Climate Corner

Following the announcement this week that 2006 was the warmest in U.S. history, Environment Canada has announced that the year was within 0.1°C of the warmest in 60 years of official Canadian records.


Prof. Michael Mann, director of the Earth System Science Center and Associate Professor in the Dept. of Meteorology at Penn State, was interviewed Wednesday on NPR's All Things Considered. The bottom line:
"There's no way to explain the changes we've seen in terms of any of these natural factors. So in that context, when we talk about recent climate change, we are talking about humans."
Mann is also one of the founders of Running time of the streaming audio (no "free, free, free" trips to Atlantic City) is 5 minutes.

Thursday, January 11, 2007

Winter Tease, or Preview of the Real Deal?


Sunny, seasonably cold. South and southwesterly breezes arriving overnight have helped moderate temperatures in the Washington metro area. Except for the missing 0.2" of snow, it has been nearly an average mid-January day, rising from a low of 26° to a high of 42°. Warming temperatures and an increasing threat of rain are on tap heading into the holiday weekend.

Tonight and Tomorrow

Increasing clouds, milder, chance of showers. Clouds will increase overnight with lows near 34° downtown, 29° 'burbtown. Tomorrow will be mostly cloudy with a 30% chance of showers developing, more likely over and west of the mountains. Highs will be in the low 50s.

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

El Niño Update

NOAA's monthly El Niño Diagnostic Discussion was released today. It indicates that "There is an increased probability of observing El Niño-related effects over North America during January-March 2007." However, "Most of the statistical and coupled models, including the NCEP Climate Forecast System (CFS), indicate that SST [Sea Surface Temperature] anomalies are near their peak and that decreasing anomalies are likely during February-May 2007."

Latest SST anomaly chart from NOAA's El Niño Page

ISO Snow

In our continuing occasional series for unrequited snow lovers, here is a place to look in the next couple of days. (And don't forget Today in Weather History.)

Political Science

In the interest of diversity, we present, without comment, the views of the John Birch Society on the NOAA 2006 climate report.

Wednesday, January 10, 2007

First Snow!


Sunny, cold. As Dan noted in his forecast below, a northwesterly breeze with peak gusts over 35 mph has produced an unusually brisk day for this winter in the Washington metro area. Temperatures reached only the upper 30s in most places; the high of 38° at National was 4° below average, but with the low of 31° the day was exactly average. This cold shot will be quite short-lived, however, as persistent troughiness to the west keeps more cold air from reaching the East Coast through the weekend.

Last night's snow showers were very skimpy in most of the immediate metro area (none observed here in MoCo Update Central), but the photo from Steve Pittman shows the first snow of the season on the ground in the Blue Ridge.

Tonight and Tomorrow

Clear, cold, then becoming milder. Clear skies, low humidity, and diminishing winds near the center of high pressure overnight should allow for some frosty lows in the mid 20s downtown to the upper teens in 'burbia. A quick wind shift to the south and southwest will allow temperatures tomorrow to bounce back smartly to the mid 40s.

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

Climate Corner

The WaPo front page 2006 climate article Dan mentioned in his earlier post has indeed become a top story. At post time, Google reported at least 287 stories on the subject, although, of course, many were reprints of the WaPo, Associated Press, and other syndicated reports. The NYT article, "Agency Affirms Human Influence on Climate", was noteworthy for confirming what we had suspected here at PM Update, that
. . . until yesterday, it appeared that no news release on annual climate trends out of the National Oceanic and Atmospheric Administration under the Bush White House had said unequivocally that a buildup of greenhouse gases was helping warm the climate.
Closer to home, the Baltimore/Washington NWS office in Sterling has released a 2006 Climate Summary detailing some significant aspects of the local climate in the past year. For Washington's 135-year record,
  • 2006 was the 8th warmest year
  • 5 of the top 8 have occurred since 1990
  • January and December were each in the top 10 of their respective months
  • April was the 11th warmest
  • August was the 8th warmest and 22nd warmest of all months
  • Total precipitation was almost 8.5" above average, the 25th wettest year
  • There was 1 measurable snow event for the year, Feb 11-12.
Oh, yeah, more snow is expected in Seattle.

Tuesday, January 9, 2007

The Beat Goes On; Some Change in Tune


Cloudy, light showers. A sunny morning has given way to a mainly overcast afternoon and scattered light showers as a very weak "clipper" and its associated upper-level energy move through the Washington metro area. The showers are in the form of snow flurries over the mountains, but to the east, they are mainly of the liquid variety.

Temperatures have peaked in the mid 40s at most locations. Today's range of 47°/32° continues the above-average streak with a +5° departure. The main effect of the clipper's passage will be to provide a reinforcing shot of cold air for the next day or so.

Tonight and Tomorrow

Clearing, cold. After some possible lingering light showers or flurries this evening, skies will clear overnight with lows a couple of degrees cooler than last night: near 30° downtown and low to mid 20s 'burbside. Tomorrow will be sunny and breezy with some scattered clouds and highs near 40°.

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

Mediarology: Hype, Hype, Hooray!

Unless you've been living in a cave lately, you've been treated to a full dose of media hype-ocracy in the form of "explanations" for the recent warm spell. Many of these rival the profundity of the statement that "Poverty is caused by lack of income." Mainly, they have taken the form of the Point/Counterpoint:

"It's Global Warming, head for the hills!"
"No, Jane, it's just El Niño, and besides, it's snowing like crazy in Denver; nothing to see, just move along!!"

Before PM Update could untangle the ideology and agenda-mongering from the science, however, the climate scientists at have sorted things out rather nicely in their latest post, entitled, "El Niño, Global Warming, and Anomalous U.S. Winter Warmth". As usual, they have managed to convey some subtle scientific concepts in a form that should be understandable to anyone who is willing to approach the subject with an objective viewpoint.

The El Niño phenomenon was known to oceanographers in the early part of the 20th century, but it was only in the latter portion of the century that serious work was done to associate it with atmospheric effects. Jerome Namias, the legendary father of modern extended-range forecasting, in a paper published about 30 years ago, clearly stated the problem that is still being resolved today:
In large-scale air-sea interactions such as El Niño it is presently almost impossible to prove cause and effect. . . Probably the sea is both slave and master of the atmosphere--a complexly coupled system.
(For the record, the media are apparently not all knuckleheads when it comes to complex scientific problems. NBC News was reported to have managed to keep things relatively straight. Warning: If you click on the preceding link, do not avoid the "About Me" section. You have been warned.)

Graphic courtesy of NOAA and

Monday, January 8, 2007

Blast From the Past


Sunny, breezy. Temperatures have been falling slightly this afternoon under northwesterly winds gusting over 30 mph at times, but the main change has been in the humidity. While the temperature fell 1° in 6 hours from 9am to 3pm, the dewpoint plunged from 50° all the way to 22° (and 4 more degrees in the next hour). In the meantime, the high for the day reached 56° early in the afternoon.

While dropping only to near average January levels, temperatures in the next couple of days will seem especially cold after the warm spell we've been experiencing. There is even the possibility of some scattered flurries to go along with the more wintry temperatures.

Tonight and Tomorrow

Clear, cold, flurries possible. Under clear skies tonight, lows will range from the low 30s downtown to mid and upper 20s in the 'burbs. Tomorrow will be partly cloudy and seasonably cold, with highs near 44°. There is a 30% chance of some light snow flurries or sprinkles, especially in the afternoon.

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

Reasoning By Analogy

Analogies are always imperfect, so forecasting from past analogs is a lot like driving while looking in the rear view mirror. Nevertheless, looking at past patterns can provide what the math guys call an "existence proof" and therefore give some clues as to which of the infinite number of possible states of the atmosphere are "preferred." The recent pattern of an upper-level low pressure trough in the West and a high pressure ridge in the East is similar in a lot of ways to the pattern of January 1950, which was by far the all-time warmest January in the 130+ years of official records in Washington. The monthly average of 48° that month was more than 1° higher than the second highest January in 1932 and more than 4° higher than the third place holder, 1890. January 1950 was responsible for 5 daily temperature records which stood until this year. The record for the 6th is the one which was broken on Saturday.

The chart shows the daily highs and lows for January 1950, along with the trend of the month-to-date average for that year and the average for this year so far. Note that after building warmth in the first week, January 1950 went through a series of progressively cooler cycles through the second and third week, finally culminating in the all-time warmest Washington January day, 79° on the 26th. That day was so spectacular that it got its own article in the Monthly Weather Review. The pattern finally broke down during the middle of February. chart from NWS data, photo © Kevin Ambrose

Mediarology: Capitol Climate

Today's Diane Rehm Show on WAMU (88.5 FM) featured a discussion of the prospects of climate policy action in the new Congress. Guests were: John Fialka, environment and energy reporter for "The Wall Street Journal"; Felicity Barringer, reporter, New York Times; Sen. Jeff Bingaman, (D-NM), new chair of the Senate Energy Committee; James Connaughton, chair, White House Council on Environmental Quality. Streaming audio is available online, and the show is scheduled to be rebroadcast tonight at 9:00.

Also from NPR were reports yesterday on the impact of this winter's temperatures on central Maine and an interview with Robert Henson, author of "The Rough Guide to Climate Change".

Seasonal Outlook

Latest seasonal forecast: Click here.

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