The Weather Guys

What is the hurricane forecast for this year?

Posted on June 24, 2019 by WeatherGuys Editor

An onlooker checks out the heavy surf at the Avalon Fishing Pier in Kill Devil Hills, N.C., as Hurricane Florence approaches the east coast Sept. 13. This year’s official hurricane season runs from June 1 through Nov. 30. (Photo credit: Gerry Broome, Associated Press)

A hurricane is a tropical storm over the Atlantic Ocean basin. The official hurricane season runs from June 1 through Nov. 30.

But that doesn’t mean all hurricanes have to occur during that time period. Indeed, we have already had a hurricane on May 20. That storm is named Andrea. Hurricanes are given names to improve communication between forecasters and the public regarding forecasts.

The National Oceanic and Atmospheric Administration has been making seasonal hurricane forecasts for about the last decade. Their Atlantic Hurricane Season Outlook for this year indicates there is a 70% likelihood of having nine to 15 named storms of which four to eight could become hurricanes, including two to four major hurricanes.

A tropical storm is named if the wind speeds are 39 mph or higher. A hurricane has winds of 74 mph or higher, and a major hurricane has winds of 111 mph or higher. On average, the Atlantic Ocean sees 12 named storms, six hurricanes and three major hurricanes.

So, if the forecast holds up, we are in for a near-normal hurricane season. NOAA’s Climate Prediction Center will update the seasonal outlook in August just prior to the historical peak of the season.

The forecast is based on current and expected conditions. First, an active season would be predicted if the sea surface temperatures are warmer than normal. Warmer temperatures increase evaporation off the sea surface and that provides the energy for the storm.

The forecast is also a function of the El Niño conditions in the Pacific Ocean. We are currently in weak El Niño conditions and, on average, El Niño years are low-hurricane years.

Perhaps surprisingly, the atmospheric pressure pattern over the Arctic also plays a role in the forecast: high pressure means a weaker jet stream, which favors hurricane development.

Category: Uncategorized

Comments Off

Has this been an unusually dreary spring?

Posted on June 17, 2019 by WeatherGuys Editor

From April 1 to June 13, Madison Wisconsin was 0.46 degrees cooler than normal and accumulated 1.94 inches above normal precipitation, some falling as snow as late as April 27!
(Photo by J. Hart, State Journal archives)

With astronomical summer set to begin on Friday morning at 10:54 a.m. in Wisconsin, it seems like a good time to consider the nature of this seemingly dreary and cold spring that we have just endured.

Almost no one will disagree that this year has had a memorably bad spring, not only locally but around the nation as widespread flooding has put elements of the agricultural sector well behind their normal schedules.

From April 1 to June 13 we have averaged 0.46 degrees below normal in Madison and we have accumulated 1.94 inches above normal of liquid equivalent precipitation, some of it falling as snow as late as April 27.

In the previous four springs we have had similar experiences only once. Some may recall that last April 1 through June 13 we were 0.36 degrees colder than normal and accumulated nearly 7 inches of snow on April 18. In the prior three years during the same period we averaged 1.94, 0.71 and 2.19 degrees above normal. None of these years was notably warm during the period but these recent records do suggest that this year presents a relatively unusual set of circumstances.

In fact, it may be that we have not had such a persistently cool spring since 1997 when April was 3.3 degrees below normal, May was 6 degrees below normal and the first 13 days of June averaged 1.75 degrees below normal, leading to an overall departure of 4.16 degrees below normal for the same period in that year.

So, though we have been waiting for spring to transition to summer, we had it much worse 22 years ago.

Category: Climate, Meteorology, Seasons

Comments Off

Is that photo of circular lightning?

Posted on June 10, 2019 by WeatherGuys Editor

Some see the shape of Wisconsin in this looping lightning bolt that struck near Hager City Wisconsin on May 31. (Credit: Jerry Zimmer)

When we see a flash of lightning, it looks as though it forms all at once.

However, a lightning bolt is actually produced in many steps. The bolt occurs so quickly that it looks like a single brilliant flash, but high-speed photography can reveal several distinct bolts.

Lightning is a huge electrical discharge that results from the rising and sinking air motions that occur in thunderstorms. Lightning can travel from cloud to cloud, within the same cloud, or between the cloud and ground. The lightning in the accompanying photograph appears to be cloud-to-ground lightning.

A typical cloud-to-ground flash begins as negative charges in the cloud that travel toward the ground in a sequence of spurts. These spurts of negative charges are called “leaders.”

Leaders travel a few hundred feet. From the lower end of one leader, another leader forms, and from the lower end of that leader, another. The negative charges hop downward from leader to leader, forming an ionized channel.

Each leader heads in a direction that is independent of the previous ones. Leaders can split, forming tree-like branches resulting in a path that is not a straight line. Most lightning appears jagged because of this, but it also can take a curved path, as in this photograph.

As the negative charges approach the ground, there is an upward stream of positive charges. When the two streams meet, an initial flash occurs in the channel and electricity flows back and forth between the cloud and ground, lighting up the sky.

The ionized channel formed by the leaders is three-dimensional. So, while the bolt in the photograph looks like a 2-D outline of our state, it could be a 3-D spiral that just appears 2-D as we look along its axis. Either way, it is a fantastic and unique photograph.

Category: Meteorology, Phenomena, Severe Weather

Comments Off

Why was the sky hazy on Thursday and Friday?

Posted on June 3, 2019 by WeatherGuys Editor

Satellite view of wildfire smoke over the Upper Midwest. Via GOES East (GOES-16)

There have been large forest fires in northern Alberta, Canada, and the smoke has drifted over the Midwest, including Wisconsin.

Smoke can cause the sky to appear hazy, even if the smoke is high above the ground. The smoke scatters sunlight to make the sunlight diffuse and grayish. When the smoke is thick, it can cause brilliant red sunsets and sunrises, as it did on Thursday. 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 of which smoke is composed, scatter violet and blue light more effectively than other colors.

So, as the sun sets and its rays pass through the smoke plume, all the blue light is 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.

Winds will sometimes transport the smoke down to the ground, resulting in a reduction in the quality of the air we breath. The small particles that make up the smoke can cause respiratory problems, particularly for children, the elderly and people with asthma.

Smoke doesn’t have much of an effect on our temperature or precipitation. However, official weather reports include observations on sky conditions and visibility.

Category: Phenomena, Weather Dangers

Comments Off

Do cell phones network with weather forecasts?

Posted on May 28, 2019 by WeatherGuys Editor

Use of ultrahigh radio frequencies by 5G wireless carriers could interfere with weather predictions. (Image source: SSEC)

Cell phones do not directly interfere with weather forecasts. However, there is concern with how cell phone signals travel through the atmosphere, particularly the 5G network.

The 5G technology is designed to carry more data and make wireless connections faster.

In March, the Federal Communications Commission began auctioning off ultrahigh radio frequencies for use by 5G wireless carriers.

These frequencies are appealing to telecommunication companies because they need to add capacity in urban areas to keep up with increased demand. But these 5G networks have unintended consequences.

Objections are being raised the National Oceanic and Atmospheric Administration and National Aeronautics and Space Administration and other federal agencies. Use of these frequencies for 5G could interfere with weather predictions.

The airwaves being auctioned are near frequencies used by NOAA satellite instruments to observe water vapor, rain and snow. For example, atmospheric water vapor emits a small amount of energy at these ultrahigh radio frequencies. Weather forecasters measure these signals from satellites and use the observations to understand how weather systems are likely to develop.

If networks transmit frequencies where water vapor emits energy, the satellite measurements will not be able to distinguish between those signals generated by the weather systems and the telecommunication signals. Loss of this weather information will impact the accuracy of weather forecasts.

Dr. Neil Jacobs, the acting NOAA administrator who oversees the National Weather Service, told Congress that loss of these weather data could reduce today’s forecast skill to what it was back in 1980.

This could become a global problem if other countries follow the US in using these frequencies for telecommunication. This fall, the World Radiocommunication Conference meets to set global agreements on use of radio frequencies for 5G.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison Department of Atmospheric and Oceanic Sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.

Category: Severe Weather, Uncategorized

Comments Off