New technology from the University of Wisconsin will help with preparation of more detailed forecasts and provide more reliable information to meteorologists and emergency planners, which should ultimately result in better, safer outcomes for public safety.
The Advanced Dvorak Technique (ADT) is a satellite-based method for determining tropical cyclone intensity. Planned upgrades include the use of full-resolution images from weather satellites, better identification of the location of each storm’s eye and the ability to better analyze hurricanes occurring outside tropical regions.
Developed by researchers at the University of Wisconsin—Madison Cooperative Institute for Meteorological Satellite Studies (CIMSS), the ADT provides an indication of how a storm might strengthen, especially one approaching populated coastal areas.
Both 2020 and 2021 were very active Atlantic hurricane seasons, and if this year proves to be anything like the last two, the upgrades will be welcomed.
How Will It Be Used?
“For us, the goal is to provide a tool so forecasters can do their jobs better,” said Tim Olander, Researcher at the University of Wisconsin’s CIMSS in a news release.
The release also noted because landfall preparations and evacuations are costly and disruptive, “accurate forecasts aided by the ADT can have huge implications for emergency planners who must decide whether to issue an order, and for residents who must follow it.”
One of the upgrades to the ADT plans to tackle the issue head-on by providing better identification of the location of the center of circulation (often called the eye of the storm).
“Pinning down the center of circulation with the greatest degree of accuracy is very important to the National Hurricane Center (NHC), as it helps us begin the forecast process with the best initial conditions, which will likely make the track forecasts more accurate,” said John Cangialosi, Senior Hurricane Specialist at the NHC. “In addition, the ADT itself works better when the center position used in the technique is more accurate, which in turn will provide better intensity estimates to NHC.”
There are a lot of different ways to get information for tropical forecasts. One of the most valuable is from hurricane hunters who fly planes directly into tropical systems to gather critical data used by forecasters at the NHC. The problem is, tropical systems are fluid and constantly changing, and hurricane hunters cannot fly 24/7 through each and every storm.
With more data, forecasters can reduce errors in the future path of the storm’s track, what is called the forecast cone of uncertainty. Being able to narrow it down, even a little bit, can help city planners, emergency managers, and local residents know when to evacuate.
“When NHC is flying hurricane hunter aircraft into storms, they primarily rely on that ‘ground truth’ for current intensity estimation,” explained Phil Klotzbach, research scientist at Colorado State University (CSU). “However, when there are no planes, NOAA relies on a variety of satellite-based estimation tools to assess a storm’s current intensity.”
One of those tools includes the subjectively-analyzed Dvorak estimates from the Tropical Analysis and Forecast Branch as well as the Satellite Analysis Branch. The analysis from those tools and others goes directly into the forecasts.
“In addition to those subjectively-based analyses, the ADT also runs in automated fashion about every 30 minutes providing storm intensity estimates,” Klotzbach noted. “You can see how NHC blends these tools together in some of their forecast discussions from Hurricane Sam last year.”
The new software to improve the ADT storm center positions is called Automated Rotational Center Hurricane Eye Retrieval (ARCHER).
Olander pointed out previous versions of the ADT used infrared (IR) imagery, which unlike visible imagery, is available at all times of the day. But the new version has additional imagery to assist with forecasting.
“The technique uses multispectral satellite data to provide a much improved storm center determination over just using IR imagery alone,” Olander emphasized.
In addition to Atlantic basin hurricanes, the system works well for tropical storms in other oceans, where direct measurements can be more difficult to come by.
“It is important to be able to estimate a storm’s intensity to help emergency planners prepare for any storm that may interact with coastal regions and population centers as well as nautical interests such as shipping and military,” Olander added.
“Places like Canada, United Kingdom, and Europe are very interested in these types of storms and how it may affect them since they can cause a lot of damage,” Olander outlined. “Extending the ADT to provide intensity estimates when the storm is in these regions can be a tremendous aid to forecasters in those areas.”
Another Busy Season?
CSU is just one of more than a dozen academic institutions, government agencies, and private forecasting companies putting out seasonal projections.
CSU’s Tropical Meteorology Project team released its annual Atlantic basin hurricane seasonal forecast earlier this month, calling for 19 named storms this hurricane season, which is five more than normal. Of the 19 storms, nine are expected to become hurricanes, and four are expected to become major hurricanes of Category 3 or higher.
Climatologically, about 30 percent of all Atlantic hurricanes make U.S. landfall. However, you don’t need to have all of the forecast storms make landfall in the United States for it to be considered an eventful season.
“It’s important to understand that it doesn’t matter if there’s 20 storms or one; if it impacts you, it’s a busy season,” said Haley Brink, CNN Meteorologist.
The probability of a major hurricane making landfall along the U.S. coastline is now 71 percent, well above the average of 52 percent for the past century, according to the CSU report.
Statistics like those demonstrate why it is important to start preparing now, by reviewing your evacuation plans and ensuring your evacuation kit is in order and up to date.