Is hurricane forecasting improving?

Posted on October 7, 2015 by WeatherGuys Editor
Hurricane Joaquin taken at night by Astronaut Scott Kelly from the International Space Station on 2 Oct 2015.

Hurricane Joaquin taken at night by Astronaut Scott Kelly from the International Space Station on 2 Oct 2015.

The improvement in hurricane track is due to a number of factors. We now have better and more satellite observations, new observations from drones carrying weather instruments, and more aircraft with better instruments observing hurricanes.

Super computers that are faster improve forecast models by allowing more energy and dynamic processes to be incorporated more explicitly into the forecast. Due to improved observations, we can include better descriptions of the initial state of the atmosphere into the models, which leads to more accurate predictions of a storm’s behavior.

Forecasting the intensity of a hurricane hasn’t improved much in the last two decades, so work remains to be done in that area. This lack of improvement is likely a result of our lack of understanding of the physics that control these massive weather systems.

Hurricanes are complex, large and powerful, which makes them difficult to study. While we still lack the ability to accurately forecast hurricane intensity, our understanding of how hurricanes evolve, how they interact with dust outbreaks from Africa, and how a new eye begins to develop around the old eye of a hurricane, has grown substantially.

Category: Meteorology, Severe Weather, Tropical

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What does El Nino mean for southern Wisconsin’s winter this year?

Posted on September 28, 2015 by WeatherGuys Editor

El Nino is an atmosphere/ocean phenomenon in which the waters of the eastern equatorial Pacific Ocean are warmer than normal for an extended period of time.

This unusual warmth forces changes in the distribution of deep convective thunderstorms over the tropical ocean which, in turn, affect the position and strength of the jet stream. Since the jet stream acts a conduit of winter storms and can regulate intrusions of cold arctic air, changes in jet stream characteristics can have a profound influence on our winter weather.

Generally, El Nino is associated with warmer than normal winters in the western Great Lakes states so we can reasonably expect that this coming winter will be milder than the last two. Though there is a tendency for a bit more precipitation in El Nino winters here, since it is usually warmer than normal, there is usually less than the normal amount of snow.

Currently, the sea surface temperature data in the equatorial Pacific suggest that this year’s El Nino may be the strongest on record. If it continues to grow in intensity as predicted, our winter could become memorably mild. One of us recalls throwing rocks into Lake Mendota in late February 1998, near the end of the last really strong El Nino winter, and imagining that might never happen again. Perhaps it will.

Category: Meteorology, Phenomena, Seasons

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When is the autumnal equinox?

Posted on September 23, 2015 by WeatherGuys Editor

On Wednesday morning, we will officially enter fall as the autumnal equinox occurs at 3:20 a.m.

On Wednesday, in common with every location on Earth, we will enjoy exactly 12 hours of daylight and 12 hours of night.

Of course, 12 hours of daylight in Madison (latitude 43N) is substantially different from 12 hours of daylight at the North Pole (latitude 90N) where the sun will barely be visible above the horizon for the 12 hours of “daylight.” On the very next day, the sun will not appear above the horizon at the Pole and will not come back for six months. As the days march on, the same fate will gradually overtake other latitudes in the Northern Hemisphere until by Dec. 21, the sun will not rise even at 66.5N.

The primary means by which air is warmed is by its contact with the surface of the Earth that, when the sun shines, can absorb radiation and heat up.

A leading consequence of the shortening days, especially at high latitudes, is that air masses can begin to get really cold again. Even as we enjoy one the warmest Septembers in quite some time, the areal extent of the cold wintertime air is growing at high latitudes.

As it encroaches southward from the Pole, the polar jet stream, always on the warm edge of the coldest arctic air, begins to take up residence at lower latitudes bringing with it the powerful storms of late autumn and winter.

So, enjoy these beautiful early fall days we are having in Madison because the cosmic deck is stacked against us.

Category: Meteorology, Seasons

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When does the first freeze occur in fall?

Posted on September 16, 2015 by WeatherGuys Editor

The cooldown that we enjoyed over the weekend, after the prolonged warm and humid spell that began September, got us thinking about the inevitable first morning with a temperature below 32 degrees.

We are less than two weeks away from the autumnal equinox, the last day until late March on which the day is at least as long as the night.

In the last 73 years, since the official temperature for Madison has been recorded at the airport, the average date of our first 32-degree night is Oct. 1. However, the earliest such night occurred on Sept. 11, 1955 – after a summer in which a record 40 days with a high temperature of 90 were recorded. This early freeze was nearly equaled by 1962 and 1963, when it occurred on Sept. 12.

More recently, the only fairly early date for the first freeze was Sept. 16, 2007. The latest such night also occurred in the 1950s – Oct. 17, 1959 – with a more recent competitor landing on Oct. 14, 2005.

Interestingly, for a period of 23 years (1940-1963) we have simultaneous records from the official recording site that used to be located in Downtown Madison. The average first freeze at that location is much later, around Oct. 20. The earliest and latest dates at that site are also quite different.

So, though on average the first freeze occurs about 10 days after the equinox at the airport, your own home may record a substantially different first freeze date.

Category: Climate, Seasons

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Is the smoke from western forest fires affecting our weather?

Posted on September 11, 2015 by WeatherGuys Editor

This year there have been many fires on the west coast of the U.S. and Canada.

Most of these fires are in remote regions and were started by lightning strikes. This smoke has drifted over our region. It will not have much of an effect on our temperature or precipitation. However, official weather reports include observations on sky conditions and visibility.

The smoke can cause the sky to appear hazy, even if the smoke is high above the ground. When the smoke is thick it can cause brilliant red sunsets and sunrises. When light beams interact with particles suspended in air, the light can be scattered or absorbed.

The amount of light that is being scattered is a function of the number of particles and the size of the particle relative to the wavelength of the light falling on the particle. Small particles, like those smoke is composed of, scatter blue light. So, as the sun sets and its rays pass through the smoke plume, all the blue lights are scattered out of the path between the setting sun and your eyes, leaving just the red and orange colors.

This results in the sun having a bright red color when it is low on the horizon. Recently, the smoke above us has been thick enough that the red sun disappeared from view before it set below the horizon.

If the winds are right, the smoke can be transported down to the ground. This can cause a reduction in air quality. The small particles that make up the smoke can cause respiratory problems, particularly for children, the elderly and people with asthma.

Category: Meteorology, Phenomena

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