by When tropical meteorologists look at satellite images, they often spot subtle cloud formations that suggest something more ominous.
The first signs of a potential hurricane can be seen days before a severe storm develops. Thin, outwardly radiating cirrus clouds, the appearance of curved streaks of low-lying clouds, and a drop in air pressure are all clues.
These early clues are critical to predicting the onset of a potentially catastrophic hurricane.
I am a meteorology professor at Penn State University and my research group uses satellites and computer models to improve the prediction of tropical weather systems. With a particularly severe storm season in the Atlantic predicted for 2024, it is more important than ever to recognize these early signals and provide early warnings. Here’s what forecasters are paying attention to.
Conditions are ripe for a hurricane
Hurricanes typically begin as atmospheric tropical waves, areas of low pressure associated with thunderstorm accumulations. As these tropical waves move westward across tropical oceans, some of them may develop into hurricanes.
The formation of a hurricane depends on several specific conditions:
Distance from Equator: Tropical cyclones typically form at least 5 degrees from the equator. This is because the Coriolis force, which is crucial for the initial rotation of the cyclone system, is weaker near the equator. The Coriolis force is caused by the Earth’s rotation, which causes moving air to spin and swirl.
Warm sea surface temperatures: For a hurricane to form, the sea surface temperature must be at least 26.5 degrees Celsius (about 80 Fahrenheit). The warm water provides energy that powers the storm as the storm absorbs heat and moisture from the ocean.
Atmospheric Instability and Humidity: For tropical cyclones to form, the atmosphere must be unstable. This means warm surface air rises and stays warmer than the surrounding air, allowing it to continue rising and form thunderstorms. There also needs to be sufficient moisture, as dry air can cause clouds to evaporate and weaken upward movement during thunderstorms. These factors are essential for the formation of frequent thunderstorms within tropical waves.
Low vertical wind shear: Strong vertical wind shear can tear apart a developing hurricane. Vertical wind shear is changes in wind direction or speed at different altitudes. It disrupts the formation and growth of a storm and makes it difficult for a hurricane to keep its vortex in line.
Early predictions require more than just satellites
Detecting the early stages of a hurricane’s life cycle has been a major challenge because there are not many surface stations and weather balloons that could provide detailed atmospheric information over the open ocean.
Once a storm begins to form, the National Oceanic and Atmospheric Administration’s hurricane-hunting planes often fly through it, taking measurements and dropping sensors to get more data. But that may not be the case for every patch of cloud, especially if the developing system is far from the coast.
One of the most important tools meteorologists currently use to predict early hurricane formation is satellite imagery, which provides real-time data on cloud patterns, sea surface temperatures and other atmospheric conditions. For example, GOES satellites operated by NOAA help meteorologists track hurricane development with unprecedented clarity. These satellites can capture images at multiple wavelengths, allowing forecasters to analyze different aspects of the storm, such as cloud formation, precipitation and lightning activity.
However, satellite observations alone do not provide meteorologists with enough information to know which tropical waves are likely to develop into hurricanes.
To improve forecast accuracy, our research group has developed methods to integrate real-time satellite data, including humidity and cloud patterns, into computer forecast models. This process, called data assimilation, allows for a more accurate and consistent representation of atmospheric conditions. This allows forecasters to benefit from significantly improved forecasting capabilities, particularly in predicting the formation and progression of hurricanes.
We are currently working with NOAA to refine these techniques and use them more broadly for better hurricane forecasting and earlier warnings, giving the public more time to prepare.
As people across North America and the Caribbean prepare for what is expected to be a particularly violent hurricane season in 2024, the need for accurate early storm forecasting has never been greater.
This article was republished from The Conversation, a nonprofit, independent news organization that brings you facts and trusted analysis to help you understand our complex world. It was written by: Xingchao Chen, Penn State
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Xingchao Chen receives funding from NOAA, DOE, NASA, and ONR.
