(Washington Post) – It has been just four months since the last hurricane season ended, but it’s already time to look ahead to the next. June 1 marks the traditional starting date, and Colorado State University’s hurricane research team released its initial predictions for the upcoming season Thursday morning.
The group’s outlook calls for a total of 13 named storms. Breaking it down further, the outlook ventures that five of those will become hurricanes and two will become major hurricanes, meaning they will be Category 3 or stronger. This outlook does not attempt to determine where storms might develop or how many might make landfall in the United States.
This year’s outlook is similar to what’s considered an average season: 12 named storms, six hurricanes and three major hurricanes. The number of storm is close to normal, but the overall activity – based on the intensity of storms and their energy – is forecast to be slightly below average.
In 2018, 15 named storms developed in the Atlantic Ocean: eight were hurricanes, and two were major hurricanes. One was Hurricane Michael. It’s been six months since that storm roared ashore on the Florida Panhandle as one of the most intense hurricanes to ever hit the United States. With winds up to 155 mph, the Category 4 leveled buildings and structures in Mexico City.
Hurricane Michael’s winds were just shy of making it a Category 5 storm, but for all intents and purposes, it was the worst-case scenario for Mexico Beach and its surroundings near Panama City. It was the third-strongest hurricane on record, in terms of pressure, to make landfall in the United States, and it had the strongest winds since Hurricane Andrew made landfall in 1992. Economists predict Michael will cost $25 billion.
Earlier in the season, Hurricane Florence made a slow-motion landfall in the Carolinas and unloaded more than 30 inches of rainfall that flooded the region for days. More than a dozen rivers crested at major flood stage, characterized by catastrophic property inundation and evacuations. Florence broke flooding records set during hurricanes Floyd in 1999 and Matthew in 2016. Damage estimates sit around $25 billion.
Now in 2019, the state of El Niño and the setup of Atlantic Ocean temperatures are two critical factors that Colorado State is considering in its outlook. Both factors are pointing to a less-active season.
During the past several months, El Niño conditions have developed in the Pacific Ocean, meaning that sea surface temperatures in the eastern tropics are warmer than normal. In general, El Niño conditions tend to suppress Atlantic hurricane formation, as a result of increases in upper-level winds that tear apart developing Atlantic hurricanes.
Predicting changes in El Niño is extremely difficult during the spring season, so although we know there’s an El Niño now, we don’t know whether it will continue through the rest of the year.
Very small changes in wind conditions can cause big changes in the ocean circulation at this time of year. Consequently, the models that forecast El Niño tend to have less skill, which is the measure of the accuracy of the prediction vs. what really happens. Nevertheless, these models do have modest ability to predict conditions for the next several months.
The latest suite guidance indicates a relatively high chance that El Niño will continue through the peak of the Atlantic hurricane season (August through October). Colorado State agrees with the majority of these models and anticipates El Niño conditions will persist through this year’s hurricane season.
North Atlantic sea surface temperatures
The tropical Atlantic is currently slightly cooler than normal, and the far North Atlantic is much warmer than normal. The subtropical Atlantic is much warmer than normal. This ocean temperature pattern is typically what is observed in less-active hurricane seasons, since strong hurricanes tend to form in the deep tropics.
How good are the forecasts?
April’s is the first forecast issued by Colorado State each year. These forecasts are then updated June 4, July 2 and Aug. 6. The forecast skill increases closer to the peak of the season. The April forecast shows modest skill, while the June, July and August forecasts show improved skill levels. Typically, El Niño forecasts improve, and the SST pattern in the Atlantic also has increased predictability as you move from spring to summer. While the Atlantic hurricane season starts June 1, about 95 percent of all major hurricanes occur after Aug. 1.
What other seasonal forecast resources are there?
Many groups issue seasonal hurricane forecasts besides Colorado State, including government agencies, private sector weather companies and universities. The Barcelona Supercomputing Center, AXA XL and Colorado State have jointly developed a website that will display seasonal forecasts from more than two dozen contributing entities by the start of this year’s hurricane season.