Category Archives: Meteorology

How is visibility distance evaluated for a weather map?

The weather observing stations of the National Weather Service operate in fully automatic mode and have sensors that measure visibility.

These instruments sense the forward scattering characteristics of light to measure the extinction coefficient of a high intensity beam directed at a volume of air close to the sensor. This provides an accurate measurement over a range of visibilities. The use of light within the visible spectrum also allows the sensor to simulate human perception of visibility. Continue reading

Category: Meteorology

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What is latent heat?

Since the beginning of the 2023-24 snow season, Madison and Dane County have received approximately 32 inches of snow.

Snow is a form of solid water, and water is the only substance that occurs naturally in all three phases — solid, liquid and invisible gas — in the Earth’s atmosphere. Of course, that means that the 32 inches of snow began as the equivalent amount of water in the invisible vapor (gas) phase before it transformed into solid water. Continue reading

Category: Meteorology, Seasons

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Are drones used in meteorology?

Unmanned aerial vehicles, or UAVs, have been used to make weather observations for half a century. Over the past decade there has been a wider application of drones in meteorology due in part to technological developments.

Drones can provide critical research observations of weather systems. For about a decade, NOAA has partnered with NASA to fly the Global Hawk high-altitude unmanned aircraft to observe and study how hurricanes form and intensify. High-resolution photographs from low-flying drones are used to understand and document wind and flood damage associated with severe weather. They also help to better assess storm intensity based on the damage. Continue reading

Category: Meteorology, Severe Weather

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Is there any difference between ‘partly cloudy’ and ‘partly sunny’?

The National Weather Service denotes sky condition using the portion of sky covered by opaque cloud cover.

In meteorology, an okta is a unit of measurement used to describe the amount of cloud cover at a given location. Cloud conditions are estimated in terms of how many eighths of the sky are covered with opaque cloud, ranging from 0 oktas (completely clear sky) to 8 oktas (completely overcast). It does not include transparent clouds, such as thin cirrus. Continue reading

Category: Meteorology

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What were the weather highlights of 2023?

As we begin a new year, let’s look back on the weather of 2023. The most recent, and odd, weather event of the year was the warm temperature on Christmas Day, with a high of 54 degrees in Madison. That was only the seventh time since 1869 that the maximum temperature exceeded 50 degrees on Christmas.

The state received less than one-third of its usual precipitation in November. The statewide average temperature for the meteorological autumn (September, October and November) was 2.5 degrees above normal, which made it the eighth-warmest autumn on record. In October, the 4.14 inches of statewide average precipitation was 1.13 inches above the 1991-2020 normal. This helped to alleviate our drought conditions. Continue reading

Category: Climate, History, Meteorology

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