Rapid intensification: What is it and why is it important to understand?

Rapid intensification is a phrase commonly heard in August, September and October – the peak months of the Atlantic hurricane season.

The National Hurricane Center defines rapid intensification as “an increase in the maximum sustained winds of a tropical cyclone (tropical depression, tropical storm or hurricane) of at least 35 mph in a 24-hour period.

Rapid intensification is nothing new. Notable hurricanes like Dorian (2019), Michael (2018) and Harvey (2017) all strengthened rapidly in the days before making landfall. Most recently, Grace (2021) and Laura (2020) also strengthened rapidly hours before landfall.

So, will Ida be the next tropical system to rapidly intensify?

As of Friday morning, Ida is a tropical storm with maximum sustained winds of 45 mph moving northwest in the northern Caribbean Sea. Ida is forecast to slowly strengthen over the next 24 hours, but this will be at a gradual rate while also interacting with the western half of Cuba.

Once Ida moves northwest of Cuba and into the Gulf of Mexico, it will enter an environment conducive for rapid development. By this, I mean Ida will be moving through an environment with low wind shear (low wind speeds with height around the hurricane), abundant tropical moisture and warm water temperatures.

With that environment conducive for rapid development in mind, the 5 a.m. update from the National Hurricane Center has Tropical Storm Ida rapidly intensifying in the central Gulf of Mexico. From 2 p.m. Saturday through 2 p.m. Sunday, Ida is forecast to have maximum sustained winds increase from 80 mph to 115 mph, a difference of 35 mph.

Additional strengthening may occur up until Ida makes landfall along the Louisiana coast Sunday evening.

DeMaria et al. (2012) found that lightning observations can provide information about hurricane updraft strength, which signifies hurricane intensity.

Black and Hallett (1999) surveyed reports of electrical activity from a large sample of aircraft flights into tropical cyclones. Their results indicated that tropical cyclone lightning within 100 km of the storm center was somewhat rare and was usually associated with fairly strong updrafts (greater than 10 meters per second).

Since Ida will be following a similar path to Laura at a similar time of year with similar environmental conditions, it is wholly possible that this system can develop into a very strong hurricane. The latest guidance from the American Model shows Ida at Category 3, major hurricane, intensity just before making landfall along the Louisiana coast Sunday evening.

You can track Tropical Storm Ida and see the most recent Tropical Update on the WRAL Weather App. Our team of meteorologists will also have the latest on our local forecast and Ida all weekend long on WRAL-TV.