DISCUSSION: Hurricanes are one of the most destructive natural phenomena on the planet. While track forecasts have improved substantially in recent decades, large improvements in intensity forecasts have been more difficult to achieve. Accurately forecasting rapid intensification (RI; increase in maximum sustained wind speed of at least 30 knots in 24 hours) has shown be especially difficult. RI can be especially dangerous near the coast. Residents can be preparing for a tropical storm or a weak hurricane, but may end up dealing with a major hurricane with little time to prepare for this more intense storm.
To improve RI forecasts and intensity forecasts in general, a better understanding of the processes important for intensification is needed in order to improve weather models. To improve our understanding, more and/or improved data is required, especially in certain high-impact areas. Hurricanes derive their energy from evaporation from the sea surface. Interaction with the ocean can also cause winds to slow down while building bigger waves (i.e., momentum exchange). Thus, understanding and observing exchanges of energy and momentum between the ocean and atmosphere are especially important for understanding changes to storm intensity.
Observations at the air-sea interface in hurricanes have been sparse because of the danger of sending manned observation platforms there and the difficulty in building unmanned platforms that can survive the high winds and waves there. A partnership between NOAA and Saildrone Inc. led to the development of a saildrone (unmanned platform that floats on the ocean’s surface and is powered by wind and solar) that can withstand conditions at the surface in major hurricanes. This platform is pictured above with the various instrumentation it carries annotated (photo credit: AGU EOS, NOAA, and Saildrone, Inc.)
During the 2021 Atlantic hurricane season, saildrones were moved into three tropical storms, Fred, Grace, and Henri. The saildrones were successful in collecting data within and surviving these storms. Then the main test came when a saildrone navigated the eyewall (most intense part of a hurricane) of category 4 Hurricane Sam. The platform survived and provided rare, if not unprecedented, views and data from the ocean surface in a major hurricane. The picture below shows a snapshot of the view from the ocean surface in this storm (photo credit: AGU EOS and Saildrone Inc.).
The saildrone data collected during 2021 and future transects through storms will provide valuable data for better understanding how transfers of energy and momentum between the ocean and atmosphere influence storm intensity. This better understanding can help improve model representation of these processes, thus, producing better forecasts.
Finally, remember that hurricane season officially starts in the East Pacific basin on 15 May and in the Atlantic on 1 June. So, if you live in an area at risk of hurricanes, start preparing now.
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©2022 Meteorologist Dr. Ken Leppert II