The Storms are Coming
Here’s the tl;dr version: the 2016 hurricane season is certainly expected to be more lively than last year. That being said, weather forecasters are split between predicting a near-normal to average season and an active to moderately active season.
And things have already been busy. While the Atlantic Hurricane season officially runs from June 1st through November 30th, 2016 got off to an early start on January 6 when the first storm, Hurricane Alex, formed off the northern coast of Cuba and wandered eastwards, becoming a full-fledged hurricane on January 14 in the middle of the Atlantic. It weakened to a tropical storm when it hit the Azores Islands (about 850 miles west of Portugal) and then later dispersed in the North Atlantic.
While Alex (even the recent short-lived tropical storm Bonnie) might herald a rough season ahead, the expectations for storm activity are mixed due to uncertainty over what’s exactly going on in both the atmosphere and the oceans.
Certain About Uncertainty
This year’s forecasts hinge on three main points:
1) A Weakening El Niño – The current El Niño/Southern Oscillation (ENSO) is fading towards a neutral state. It’s expected (75%) to transition to a La Niña between August and October 2016, the height of hurricane season. A typical El Niño produces eastward blowing wind shears off the Leeward islands in the Caribbean Sea that stretch out to the hurricane Main Development Region (MDR) — just off the west African coast. Hurricanes like to form over warm water in quiet, calmly rising air and then build into strong convection systems. El Niño’s wind shearing disrupt those air currents and make it harder for storms to form. A La Niña tends to have very little wind shearing. But how fast the El Niño transitions to a La Niña and how strong that will be isn’t precisely clear.
2) Differences in Sea Surface Temperatures (SST) – While warm water is in place off the eastern coast of the United States, colder water in the North Atlantic and off the coast of west Africa adjacent to the MDR could reduce chances for storm formation because cold water can’t provide very much heat energy to a hurricane. On the other hand, these temperatures could warm sharply over the course of the summer.
3) The Atlantic Multi-decadal Oscillation (AMO) – What does that weird “multi-decadal” adjective even mean? Well, the AMO has a climate pattern lasting 25-40 years (multiple decades!) when SSTs in the North Atlantic and the MDR are both warmer or cooler than normal. During warmer SST periods, there is above-normal hurricane activity. During cooler SST periods, there is generally below-normal hurricane activity. The question currently is whether the high-activity period that began in 1995 is ending, has ended, or is still ongoing.
Who Actually Makes These Predictions?
This year’s forecasts come from the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center, Colorado State University (CSU), the Weather Company (formerly Weather Services International), and Tropical Storm Risk (TSR), Deptartment of Space and Climate Physics, UCL (University College London).
1) NOAA’s Climate Prediction Center’s prediction calls for a 45% chance of a near-normal season — but includes a 30% chance of an above-normal season and a 25% chance of a below-normal season. This outlook is complicated by ALL the uncertainty we mentioned above.
- The rate the current El Niño fades into a La Niña and its strength.
- The status of the AMO. Has a cooling phase begun or is it still in a warm AMO phase?
- Fluctuations in Atlantic SSTs. It is unclear if the observed SST changes over the past three years are indicate changes in the AMO or if they reflect short-term variability. Sea surface temperatures in the North Atlantic and in the MDR from January to April were cooler than average. However, last year’s SST in the MDR warmed as summer progressed to becoming the 5th highest on record — which is not consistent with a cooling phase.
2) CSU forecasts an average season based on a combination of a La Niña emerging in September and the belief that the AMO has entered a cold phase. This means cold water in the North Atlantic might interact with strong Atlantic high pressure circulations to drive ocean currents carrying cold water southward to the MDR.
3) The Weather Company forecasts an active season later during the August-October months due to the cold waters warming in the MDR and the expected La Niña developing. They also foresee the hottest summer since 2012 throughout the majority of the US, especially in northern states.
4) TSR forecasts a moderately active hurricane season, though it expects warmer SSTs in the MDR August-September with fading winds shearing due to the emerging La Niña. How fast the La Niña emerges and how strong it might be fuel the prediction’s uncertainties.
Additional apdates from CSU and NOAA’s National Hurricane Center will appear later in June 2016. NOAA also issues an update in early August right before the seasonal peak. We will provide you a recap of those updates at this time, so watch the blog!
It only takes one storm to cause a tragedy. Hurricanes are not merely limited to the coastal areas. They can have a devastating reach inland as well. Make sure you and your family are prepared and have a plan. Be sure to check out NOAA’s National Hurricane Preparedness Week as well as these other helpful storm resources.
- Hurricane Prep: Before, During, and After the Storm
- How Hurricanes Impact You
- Hurricane Evacuation Planning