Clammy Whammy

Now

Showers and cool. After moderate to heavy rain overnight, precipitation has become more intermittent in the Washington metro area this afternoon. Radar is still showing some pockets of moderate to heavy rain over the Eastern Shore, with heavier amounts south and east of Ocean City.

The official temperature, which peaked at midnight at 57°, has fallen through the day to 52° at mid afternoon. Northeasterly winds have been gusting to near 30 mph at times. The dampness will be slow to move out of the area as this nor'easter uncharacteristically drifts gradually southward under the influence of an upper-level "cut-off" low.

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

Tonight and Tomorrow

Continued clammy. Temperatures will remain in the low 50s overnight with continued showers and drizzle. Precipitation chances will decrease during the day Saturday to near 30% by evening. Overcast skies will persist, although a few breaks in the clouds are possible by late in the day. High temperatures will be mainly in the upper 50s, with some low 60s possible in places that see some sunshine, most likely in the northern portion of the region.

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

Tropical Topics

Atlantic tropical activity has perked up slightly with the development of a poorly organized low pressure area about 360 miles west-southwest of Bermuda. This has some potential to become a subtropical storm. A reconnaissance flight is tentatively scheduled for tomorrow to investigate.

Blogrolling

A tip of the hat to the aptly-named METroblogging DC, which reviewed CapitalWeather.com as "the first in an ongoing series about the best & brightest of the online resources and writings that exist in or for the DC area." (Note to the Metrobloggers, however: "CapitalWeather" contains no "o".)

Warm Up the Fireplace and DVD Player

Now

Cloudy and cool. The passage of a cold front last night has brought clouds and much cooler temperatures to the Washington metro area, but no rain so far. After a high of 75° at 2am this morning, temperatures have dropped steadily to the low 60s this afternoon. A low pressure area developing over Kentucky will bring increasing chances of showers and rain tonight through tomorrow and into the weekend.

Tonight and Tomorrow

Rain developing, cool. Showers are likely to develop by about midnight, with rain becoming steadier by morning and lows in the mid 50s. Tomorrow will be damp and quite cool with showers continuing through the day and highs only a few degrees above the lows, mainly in the mid 50s. (The record lowest maximum of 45° for Oct. 6 will not be in jeopardy.) The latest model output this afternoon indicates that the heaviest amounts of rain through early Saturday afternoon will be in central and southeast Virginia and eastern North Carolina.

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

Tropical Topics

This parrot is still dead.

El Niño Update

NOAA's Climate Prediction Center/NCEP updated their El Niño outlook today. The latest sea surface temperature (SST) departures from average are more than 0.5°C across most of the equatorial Pacific, with some places as high as 1.5° above. The overall outlook is for El Niño conditions to persist through early next year. In an email interview with Reuters, CPC Development Branch Chief Vernon Kousky said,

It is safe to say that the current event will not strengthen to the level of the 1997-98 event. This event started several months later and is considerably weaker than the very strong 1997-98 event. The strongest El Nino events form during March-May.

Good While It Lasted

Now

Sunny and warm. This afternoon's Washington DC area temperatures in the low to mid 80s are a couple of degrees warmer than yesterday's, but the dewpoints in the mid 60s (relative humidities 50-60%) are making it feel even more summer-like.

Regional radar is dry as showers ahead of an approaching strong cold front have so far reached only as far as northern and western Pennsylvania.

Tonight and Tomorrow

Showers developing, becoming much cooler. Clouds will increase tonight with a 30% chance of showers after 2am. Lows will be near 60°. As Dan indicated earlier, tomorrow's forecast is a bit tricky, but today's models are indicating that skies will be partly to mostly cloudy with highs only in the mid 60s and a 30% chance of showers.

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

Tropical Topics

The tropical Atlantic is totally dead, at least for now.

El Niño Update

ABC News (Australia) reported today that the Australian National Climate Centre is confirming the development of an El Niño pattern in the Pacific: "The key indicators include sea-surface temperatures above El Niño thresholds, sustained negative values of the Southern Oscillation Index (SOI), weaker than average Trade Winds during the past two months and increased cloudiness in the central to west Pacific."

El Niño is associated with hot summers in Australia, especially in the southeast. September was the warmest ever recorded in 147 years in Sydney, with 9 days exceeding 25°C (77°F). September was also warm and dry in New Zealand.

Pictured: Current tropical Pacific sea surface temperatures and winds from PMEL/NOAA

Summer, Ver. 2.0

Now

Sunny and warm. It doesn't meet the classic definition of Indian Summer because we haven't had the first frost yet, but summer-like conditions have returned to the Washington metro area this afternoon. Most reporting locations were in the low 80s by mid afternoon, although a stubborn southerly "river breeze" kept National Airport capped at 79° for 3 consecutive hours. Dulles, on the other hand, was up to 81°.

Temperatures were at least into the 70s through most of the Mid Atlantic area, while 90s were widespread through the Southern Plains and Mid Mississippi Valley.

Temperature chart at 4pm today from Unisys

Tonight and Tomorrow

Warm, a bit more humid. Tonight's lows under mostly clear skies will be in the low 60s downtown to the upper 50s in the cooler 'burbs. Tomorrow will be much like today, but a bit more humid and with highs a few degrees warmer, near 84°.

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

Tropical Topics

The last advisory on Tropical Storm Isaac was issued at 5pm yesterday as it passed by the southeastern tip of Newfoundland. Damage reports were minimal as tropical storm warnings were cancelled.

The researchers from the tropical clime of Colorado State (Klotzbach/Gray) updated their forecast today for the remainder of the hurricane season. Although the lack of landfalling hurricanes, especially compared to the last two years, makes it appear quiet, the hurricane season through September has been near average. (August was only 45% of average, but September was 40% above average.) The forecast for October is for only 2 more named storms, including 1 hurricane, but no major (Category 3 or above) storms. The "below-average prediction for October-November activity is largely due to the rapid emergence of an El Nino event during the latter part of this summer." The forecasters note that the rapid El Nino development was not well predicted.

Commodity markets this morning reacted at least in part to this forecast by driving the price of oil below $60 a barrel. The price of natural gas has plunged even more dramatically recently, to a level about 2/3 below what it was last year after Katrina and Rita did major damage to Gulf of Mexico energy facilities.

Mediarology

Tonight's ScienceNow report on the PBS NOVA program (8:00 on channels 22 and 26 in the DC area) explores the possible effects of a rock the size of the Rose Bowl hitting Earth in 2036.

After the Fall

Now

Breezy, chilly. After yesterday's strong cold frontal passage, temperatures in the Washington metro area struggled to reach the mid 60s this afternoon. Under some puffy instability cumulus clouds and a brisk northwesterly breeze, the official high temperature is likely to be the coolest since the 64° over 4 months ago on May 19. The next system moving in from the Great Lakes this weekend will have less moisture to work with, and indications from today's latest models are that the showers associated with it are likely to hold off until Saturday night.

Tonight and Tomorrow

Continued cool. Winds will diminish tonight, and lows will be near 50° downtown to the lower 40s in the cooler 'burbs. Tomorrow will see some increasing clouds in the afternoon, but only a 20% chance of showers before evening.

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

Tropical Topics

Tropical Storm Isaac has been moving a bit more west than expected in the central Atlantic, but it is still predicted to track well east of Bermuda, brushing by Newfoundland early next week. Its 45 mph peak winds increased to 60 mph this afternon, and strengthening to a hurricane is possible this weekend.

Climate Corner

The Weather Channel's new weekly "Climate Code" program, which premieres Sunday at 5, was previewed in the hometown Atlanta Journal-Constitution yesterday with an article, "Weather Channel ready to take heat on global warming" (requires minimally annoying registration). The associated broadband channel, One Degree, was previewed in Mediaweek.

Severe Thunderstorm Watch Until 10pm

Now

Showers, thunderstorms possible. Strong southerly breezes ahead of a strong cold front approaching from the west have pushed temperatures into the upper 70s this afternoon in the Washington metro area. Instability from the surface heating, lifting from the cold front, and strong upper-level energy support have prompted a Severe Thunderstorm Watch until 10pm for DC, northern Virginia, and central Maryland.

Storms are moving rapidly from southwest to northeast, so there may be some local downpours, but the main threat is not so much from heavy rain, but rather strong, gusty winds. There have been some reports of scattered trees down in eastern West Virginia. Click on your county above for the latest watches or warnings, and refresh the page for the latest radar loop from Wunderground.com. Let us know in the Comments section of any activity in your area.

For the outlook through the weekend and beyond, including Larson's Long-Range, scroll down to Josh's post immediately below, or click here.

"I" of the Storm

Tropical Depression 9 developed late yesterday and became minimal Tropical Storm Isaac this morning with peak winds of 40 mph (up to 45 mph in the latest advisory). It is expected to follow the usual path so far this year of staying east of Bermuda.

Capitol Climate

The WaPo has been, shall we say, somewhat lukewarm in covering the subject, as we noted Tuesday in PM Update, but the paper contains an editorial today, "Heed This Warning", using the latest report from climate expert James Hansen as the basis for strongly urging an end to the current inaction in Washington on the issue of climate change. It concludes,

Most of all, it will require an end to denial -- denial that the problem exists, denial that anything can be done about it if it does and denial that the problem is urgent and requires immediate attention.

Nice Now ... Gaining Rain Later?

Now

Sunny, breezy.

A gentle southerly breeze and sunny skies have brought temperatures to the mid 70s in the Washington metro area this afternoon.

A cold front approaching from the Midwest could bring the possibility of showers by late tomorrow. For tonight's forecast and the outlook through the weekend, scroll down to Dan's post below.

Pictured: Yesterday was a great day for an outdoor lunch at Reston Town Center, by Capitalweather.com photographer Kevin Ambrose.

Precipitation Distribution: Drought or Naught?

Today is the 11th consecutive day without measurable rain in Washington, and it's been just under 2 weeks since more than 0.1" fell. Although August came in at barely 30% of the long term average, September is already nearly 40% above the average, so we're not talking about the dreaded "d" word here (especially since some folks tend to get quite exercised in the Comments section at any hint of such a mention; you know who you are!)

Looking back at the first 3 quarters of 2006, however, it does seem that there have been some interesting anomalies in the distribution of precipitation. The year so far, at just under 35", is comfortably above the 9-month average of 30". On the other hand, the 62 days with measurable precipitation are well below the average total of 85 for the year through September.

One way to look at this is by defining a "P/E" ratio (precipitation per event). This can be approximated by dividing the total precipitation for a month by the number of days in the month with 0.01" or more. (Strictly speaking, this is stretching the definition of "event", since one event can extend across multiple days.)

The chart shows that 3 of the 4 months beginning in June have had P/E ratios more than 50% above the long-term average. The August P/E of 0.34" per event was 89% of average, but the month's total rainfall of 1.03" was spread over only 3 days, or just 1/3 of the average number of August rainy days. The bottom line is that the year so far is running above average for total precipitation, but that total has mainly been achieved through a significantly smaller than usual number of events.

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