Wind Roses

No, they are not flowers that grow in windy places. A wind rose is the most common way to display statistical information about the relationship between wind speed and direction at a particular site. Basically the frequency of occurrence of winds from different directions is calculated from a dataset, and then a polar plot is constructed (similar to a bar graph) with length out from the center proportional to relative frequency. This allows a simple visual portrayal of the most common (or rare) wind directions. Just remember that meteorological convention always designates wind direction according to the direction that the wind comes from. Within each of the resulting "pie slices" of the wind rose, the relative frequency of different wind speeds may be indicated by areas of different color, similar to a "stacked" bar chart.

Wind roses are used in many applications, such as wind energy development, sailing, and air quality management.

Here is an example of a wind rose showing the winds observed at Miscou Island, New Brunswick, Canada during June 2007:



Software for creating wind roses from raw data files is available from Lakes Environmental (free) and EnviroWare. Precalculated wind roses for many U.S. stations are available online through the Natural Resources Conservations Service. More discussion and examples are available here.

Science fair projects

For students wanting to do science fair or class projects relating to the weather, there are many possibilities. Some of the most interesting however are ones that make use of actual observed weather data. The Oklahoma Climatological Survey maintains a website that lists some sample projects that have been done using data from the Oklahoma Mesonet observing network, as well as several related pages dealing with K-12 education and science fairs.

Several online data sources are listed on the Synoptic Meteorology class webpage, with wunderground.com and the NOAA weather server probably being the most user-friendly.

The Dryline

Especially in the springtime, it's common for a well-developed "dryline" to be found in West Texas. Similar to a front, the dryline is a discontinuity that separates the hot, dry (continental Tropical; cT) air of the Desert Southwest and Mexican Plateau from the warm, moist (maritime Tropical; mT) air that flows off of the Gulf of Mexico. Typically the sudden transition occurs in the vicinity of the 50°F isodrosotherm (line of constant dewpoint temperature). Whether it stays quasistationary or progresses eastward in advance of a low pressure system and cold front, the dryline holds special interest for tornado chasers and other people interested in severe storms since the area northeast of the dryline is often very favorable for initiation of severe convective storms. More than any other atmospheric feature, this is responsible for the existence of "Tornado Alley" in North Texas and central Oklahoma. The presence of dry air contributes to the generally greater visibility of tornadoes compared to tornadoes in the eastern U.S.

This afternoon there is a well-defined dryline extending as far north as western Kansas, with dewpoints in the mT air mass typically between 65-70°F and dewpoints of 10-40°F in most of the cT air mass. Although temperatures to the west of the dryline are generally warmer in the 20 Z observations, this is primarily a reflection of a larger diurnal cycle of temperature in the drier air. In early morning, the temperature gradient will often be reversed from the afternoon pattern. The dewpoint discontinuity is often maintained and strengthened by converging surface winds within a weak lee/thermal trough. When a dryline intersects a cold front, the point where they meet is commonly referred to as the triple point.

Weather Modification?

So is there actually any way that we can change the weather? While it's become increasingly well established that human activity can cause systematic climatic changes by modifying the land surface and contributing air pollution, such unintentional effects normally seem to make things worse instead of better. Of course, for every loser there's usually a winner. For example, if a drought causes crop failures in one area, then farmers in other areas may reap profits from higher prices.

The two applications that people usually think of for intentional weather modification are increasing rain over dry areas and minimizing the impact of hurricanes. Science-based rain-making has been attempted since at least the 1940s, although only fairly recently have researchers been able to show a clear improvement, under ideal circumstances. Known as cloud seeding, this normally involves injection of silver iodide or other specialized salts to help cloud droplets grow faster. Currently the big news is how much money China has invested to try to produce favorable weather for the Beijing Olympics. In general their effort is viewed with substantial skepticism.

Attempts to modify the strength or path of hurricanes have largely either been dismal failures or figments in the imagination of conspiracy theorists. For several years, the U.S. government supported research on Project StormFury, before determining that the potential for useful modification was exceeded by the inherent risks. Although federal research funding for hurricane modification has dried up, new (and old) ideas continue to be proposed. These have included moisture-absorbing gels, atomic bombs, and oil slicks.

Other areas of interest in weather modification are hail suppression (e.g. in Alberta) and clearing fog at airports.

A Big Flood on the Lower Mississippi

The current flooding along the lower Mississippi River has reached historic levels, bringing back memories of 1927, 1973, and other major flood years. So far the levees have held back major disaster though. Within the state of Mississippi, the river has now crested, barring any rises due to additional rainfall upstream. Estimates are that a couple hundred homes have been impacted. With about half of the floodgates on the Bonnet Carre Spillway now open above New Orleans, the huge amount of river water flowing into Lake Pontchartrain is now giving concerns that small boats may collide with floating debris entering the lake.

In the Mississippi Delta area to the east of the big river above Vicksburg, the current flooding has heightened the debate about a Corps of Engineers pumping scheme that appears headed for a veto by the Environmental Protection Agency (EPA).

The Father of Chaos

Yesterday Dr. Edward Lorenz died of cancer at age 90. He was a respected meteorology professor at MIT, who was the first to significantly develop chaos theory and apply it to the atmosphere. Out of that came our current concepts of atmospheric predictability and the need for ensemble methods in numerical forecasting.

Some outdoor recreation weather dangers

In New Zealand, six college students and their instructor drowned on Tuesday in a flash flood while hiking in the Mangetepopo Gorge.

Climbers in Scotland are concerned about the seasonal ending of the avalanche forecasting service while large amounts of snow remain on the mountains. Up in Juneau, Alaska, the problem is a major avalanche that knocked out transmission lines supplying power to the city.