Model Simulates Likely Spread of BP Gulf Oil Into Atlantic

A study released today by the National Center for Atmospheric Research (NCAR) shows that oil spreading from the massive BP gusher in the Gulf of Mexico is likely to move around Florida, along the southeast U.S. coast, and into the western Atlantic. The computer modeling is not a specific forecast, but it shows the likely flow based on average ocean currents in the region. The 6 simulations which were run provide an "envelope of possible scenarios for the oil dispersal." One of these is shown below:



Description from NCAR:

This animation shows one scenario of how oil released at the location of the Deepwater Horizon disaster on April 20 in the Gulf of Mexico may move in the upper 65 feet of the ocean. This is not a forecast, but rather, it illustrates a likely dispersal pathway of the oil for roughly four months following the spill. It assumes oil spilling continuously from April 20 to June 20. The colors represent a dilution factor ranging from red (most concentrated) to green (most diluted). The dilution factor does not attempt to estimate the actual barrels of oil at any spot; rather, it depicts how much of the total oil from the source that will be carried elsewhere by ocean currents. For example, areas showing a dilution factor of 0.01 would have one-hundredth the concentration of oil present at the spill site.
The animation is based on a computer model simulation, using a virtual dye, that assumes weather and current conditions similar to those that occur in a typical year. It is one of a set of six scenarios released today that simulate possible pathways the oil might take under a variety of oceanic conditions. Each of the six scenarios shows the same overall movement of oil through the Gulf to the Atlantic and up the East Coast. However, the timing and fine-scale details differ, depending on the details of the ocean currents in the Gulf. The full set of six simulations can be found here. (Visualization by Tim Scheitlin and Rick Brownrigg, NCAR; based on model simulations.)

Why Don't We Have a Specific Forecast for Inauguration Day?

You may have noticed that the discussion of the Inauguration Day weather outlook, at least so far, has been expressed only in terms of average probabilities for an entire week including the day of interest. If climate predictions can be made with some confidence well into the remainder of the century, why can't we make an accurate weather forecast less than 2 weeks ahead?

Early last year, we posted an analysis of the limits of daily weather forecasting. The upper chart to the right shows that there has been a steady increase in the skill of computer weather models, but there is essentially no value in a forecast beyond about 8 days. In spite of this, some current forecast models are routinely run out as far as 16 days. Is this just a waste of computer resources at taxpayer expense? No, it serves to generate a base of experience from which the models can continue to be improved in the future.

Because the model output is available, however, snow freaks looking for the next school cancellation, commercial weather services looking to make a quick buck, and corporate media attempting to capture more eyeballs for their pop-up, animated, cycle-sucking advertising continue to peddle the notion that a forecast for a specific day at a particular location 2 weeks or more in advance makes sense. This is not only foolish, it's also unprofessional on the part of those meteorologists who enable such activity (despite their disclaimers and caveats), and it confuses a public already being bombarded by misinformation and even deliberate disinformation on the relationships among weather, climate, and policy issues.

As an example, the 4 maps to the right are the computer model predictions for 7 am, January 20, 2009 made on each of the last 4 days (most recent at the top, oldest at the bottom). If you're not familiar with reading weather maps, the solid lines are surface air pressure, the green and blue shaded areas are precipitation, and the dashed red and blue lines are an indirect representation of temperature. You don't need to be a weatherman, however, to see that these are very different patterns.

Images (click to enlarge): Weather model skill as a function of year, from The Emergence of Numerical Weather Prediction, Peter Lynch, Cambridge University Press, 2006. Chart © ECMWF. GFS model output maps for sea level pressure, 1000-500 mb thickness, and precipitation, 7 am, January 20, 2009, from NCEP/NWS/NOAA.

Model Muttering

Note: This post is rated "G", suitable for all audiences; does not contain the weather "s" word.


Weather model skill as a function of year, from The Emergence of Numerical Weather Prediction, Peter Lynch, Cambridge University Press, 2006. Chart © ECMWF. Click image to enlarge.



In the nearly 60 years since the modern era of numerical weather prediction began, many orders of magnitude improvements have been made in both computer technology and the formulation and methods of solution of the equations describing the atmosphere. As a result, huge improvements have been made in the accuracy of daily weather forecasts. As good as the models have become, however, it's important to realize what they can and cannot do.

Click here to read entire post.

Model Muddle Temperatures to drop sharply, then some uncertainty

Now

Mostly sunny, mild. After a brief step backward, the seasonal calendar is about to take a jump forward to more wintry temperatures. What happens thereafter is subject to a bit of debate among the models, but the storm development noted in Dan's earlier post has disappeared from the run of the same model made 12 hours later.

By mid afternoon today, however, readings were well into the 60s throughout the area, with Dulles at 68° and National 66°. Salisbury, Culpeper, Leesburg, Manassas and Patuxent River all reached at least 70°. The air is also quite muggy with dewpoints generally in the mid to upper 50s.

Tonight and Tomorrow

Mostly cloudy, showers likely, then turning colder. Skies will become mostly cloudy overnight with showers likely and thunderstorms possible, mainly after midnight and through tomorrow morning. Lows will be 48-53°. Clouds will decrease tomorrow afternoon along with increasingly brisk and gusty northwesterly winds. After morning highs in the low 50s, temperatures will drop during the day to the low 40s by evening.

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

Climate Corner: New MIT Model Results

Prof. Peter Stone of the MIT Center for Global Change Science gave a very interesting presentation last night on the science behind climate change modeling. With the current model inconsistencies over what may or may not develop as soon as early next week, this is an especially relevant time to review the difference between weather and climate modeling. PM Update asked Dr. Stone how he would explain this, and his answer was very similar to what has been said here in the past, but it bears repeating:

Even though climate is the long-term average of the weather, and even though the basic laws of physics apply equally to both problems, climate modeling is not simply taking a weather prediction model and running it for a much longer time. It is much easier, and more accurate, to predict the average conditions produced from the long-term equilibrium of a set of forces than to predict the specific details of the evolution from a beginning state to some point in the future. For the more technically inclined, this is the difference between an initial-value problem (hard) and a boundary-value problem (not so much). Weather prediction is an initial-value problem; it starts from a given set of conditions and predicts the details of their change over time. Climate prediction is a boundary-value problem; it applies a set of forces to a beginning state and predicts the final equilibrium result.

In the course of his lecture, Prof. Stone disclosed some tentative results, now in peer review for future publication, regarding likely future temperature increases. Based on a "business as usual" scenario (no reduction in CO₂ emissions), his research indicates that the median prediction of the mean global temperature increase by the end of this century is 4.9°C, with a 90% confidence interval of 3.0-7.7°C. This is sharply higher than the results presented in the latest IPCC report of a range of 2.0°- 4.5°C for a doubling of CO₂. To put this into perspective, the predicted increase produces a higher mean temperature than has occurred in the last 3 million years.

The slides from Prof. Stone's lecture are available on the MIT Club Seminar Series website.

Temperature Temperance

Now

Sunny, mild. Under some scattered high clouds and a southerly breeze, temperatures have reached the 60s this afternoon in the Washington metro area; the official high was 62°. Clouds will increase tonight, and showers will arrive tomorrow, as a low pressure area developing along the Gulf Coast moves toward the Ohio Valley.

Tonight and Tomorrow

Increasing clouds, mild; showers developing. Clouds will increase tonight with lows in the upper 40s to 50°. Showers will develop after dawn tomorrow morning, continuing through the afternoon. The heaviest rain, however, should remain west of the mountains and through the Ohio Valley. Highs will be in the low 60s.

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

Warmth in Perspective

While today's temperatures certainly felt out of place for January, they were well short of the record 73° for the date. In fact, only 4 dates in January have failed to ever reach 70° in Washington. (Interestingly, this is 2 fewer than the 6 in December.) Two of them have already passed, including the lowest, 68° on the 3rd. What is noteworthy about the current warmth, however, is its persistence. The current string of 25 consecutive above-average days is longer than last January's run. Although there were only 3 average or below days in January 2006, they were scattered through the month.

The warmth is also pervasive through the whole country. The plot above of temperatures at midnight last night (from Unisys) shows only a very small extent of sub-30° temperatures (blue and blue-green), nearly all in the southern Rockies. The daily high temperature map shows above-freezing temperatures in all 48 states. I could find only 4 locations with temperatures below 32°. If you can find more, please let us know in the comments where they are located.

Modeling Myths

A common myth, especially, it seems, among operational meteorologists, is that climate models must be inaccurate simply because daily forecast models become inaccurate beyond about a week with current technology. Therefore, the argument goes, how can you possibly forecast years, decades, centuries into the future? A "Quick Study" in the latest (January 2007) issue of Physics Today called "The physics of climate modeling" helps to explain this apparent paradox. The article is open to non-subscribers and is quite accessible, no equations necessary. The key distinction between the two types of models is the following:

Weather concerns an initial value problem: Given today's situation, what will tomorrow bring? Weather is chaotic; imperceptible differences in the initial state of the atmosphere lead to radically different conditions in a week or so. Climate is instead a boundary value problem-a statistical description of the mean state and variability of a system, not an individual path through phase space. Current climate models yield stable and nonchaotic climates, which implies that questions regarding the sensitivity of climate to, say, an increase in greenhouse gases are well posed and can be justifiably asked of the models.

Unfortunately, the online version omits a figure from the carbon-based version which shows how well climate models are able to reproduce the effects from the eruption of Mt. Pinatubo in 1991, although the results are described in the text. Hopefully this will appear in the pdf version, which is not yet online.

Also pertinent to this question is the article "Belief and knowledge-a plea about language" in the same issue. It discusses how different meanings for the same words can produce misunderstandings about scientific concepts. Saying "I don't believe the results of climate models" without verifiable contrary data is simply an ideological assertion. On the other hand, the statement, "[Scientists believe that] climate is changing in many ways, and there is strong observational and scientific evidence that, at least over the last 50 years, human activities are the major contributor to climate change," reflects the current state of scientific knowledge.

DC AC

Move directly to summer. Do not pass "Go." Do not collect $200. It's air-conditioning season in the Nation's Capital region today as temperatures have soared into the 90s by early afternoon. Unlike the beautifully dry conditions over the holiday weekend, humidity is also high.

Several locations in the region with dewpoints in the 70s were reporting heat indices over 100 as early as 2pm. By 4pm, Dulles had reached 95° and National and BWI had hit 94°. The robo-observer at Frederick checked in with 97°. The highly non-standard exposure here at Afternoon Blog Central in Montgomery County briefly touched triple digits.

Temperature chart at 4pm today from Unisys

A more easterly flow should knock temperatures back into the upper 80s tomorrow, but humidity will remain sticky. For tonight, keep the AC cranked high as you enjoy the waning hours of cheap electrons before the Pepco rates ratchet up 39% in Montgomery and Prince Georges Counties at midnight tomorrow night; BGE rates will go up 72%.

Tonight and Tomorrow

Tonight's lows should be near 70 in the city to the mid and upper 60s in the 'burbs. Tomorrow will be partly cloudy and continued humid, but with highs only in the upper 80s.

Political Science: Irony is Not Dead

Joel Achenbach's cover article "The Tempest" in Sunday's WaPo Mag is a lengthy (7500 word) exploration of the skeptic mindset in the realm of climate change. It focuses mainly on Colorado State hurricane researcher, general curmudgeon, and DC native William Gray. Achenbach, whose expertise seems to be more in the area of political science than physical science, gives a fascinating view of the power of faith. In spite of the mounting evidence, Gray is seemingly unable to see the cruel irony in vehemently rejecting climate models as a hoax because models can't predict the details of the weather next month, while at the same time his own reputation rests on the statistical modeling of the number and intensity of hurricanes in a season, even though his models can't predict the details of any individual storm.

A transcript of this morning's interactive discussion with the author is available online.

Weekend Wilma Worries?

Temperatures this afternoon are about 10 degrees warmer than yesterday in the Washington DC metro area, ranging from 77 to as high as 81 in the southern portions of the region. The only precipitation east of the Mississippi consists of some scattered showers in northern New York and New England.

Tonight and Tomorrow

Under clear skies, temperatures tonight will drop to the low 50s in the city and the mid to upper 40s outside the Beltway. Tomorrow will once again be sunny and dry with highs near 76.

Tropical Beat

Wilma became a hurricane this morning; at 5pm, maximum winds were 80 mph and the storm was moving west-northwest at about 8 mph from a position about 180 miles south of Grand Cayman Island in the Caribbean. Wilma is expected to intensify to major hurricane status (Category 3) as it moves more toward the northwest and into the Gulf of Mexico, eventually turning northeastward toward southern Florida. The storm's impact on our area is very uncertain at this point; that depends on whether it is (1) picked up by a trough in the westerlies and moves up the Atlantic Coast or is (2) pushed offshore to the south.

Climate Clues: A Hard Rain

Image from Meehl et al., Geophysical Research Letters, Vol. 32, L18719.

Today's WaPo has an article describing a study being published online in the Proceedings of the National Academy of Sciences. The study used a climate model to investigate the effects of a doubling of CO2 in the atmosphere by the end of the century. The model predicted that there would be a large increase in the number of extreme heat events and also an increase in the intensity of precipitation. An article in Scientific American online explains that this model increases accuracy from older models by doubling the horizontal resolution from a distance of 50 km between gridpoints to 25 km. By way of comparison, this is almost 16 times the resolution in each horizontal direction compared to what was used routinely in daily weather forecasting just a couple of decades ago.

This study is consistent with one recently reported by NCAR, the National Center for Atmospheric Research, and published in Geophysical Research Letters, which found that precipitation would become more intense with an increase in CO2. The biggest increases would be over land in the tropics. Other areas with large increases include northwestern and northeastern North America.