2017 Hurricane Season Review

Summary:

• Above average storm activity
• Anna Maria Island evacuation for Irma, but no flooding, contrary to forecast 5′ – 15′ surge
• 2 landfalls on Florida Gulf Coast (Irma and Philippe)
• Broad swath of property damage, trees downed, and power outages across Florida from Irma
• Minor damage to Anna Maria Island properties and trees. Maximum wind reported was 92mph as the eye of Irma traveled inland of the island
• Anna Maria City Pier and restaurant damaged beyond repair

The 2017 hurricane season was more active than predicted by the Colorado State University Tropical Meteorology Project forecast team. Three major hurricanes struck the United States: Harvey, Irma and Maria, causing devastating destruction to islands in the Caribbean and other portions of the tropical Atlantic:

“The 2017 hurricane season was extremely active. Overall, our predicted numbers from our early July and August issue dates for named storm and hurricane formations were relatively close to what was observed, but our early season predictions and our predictions for integrated metrics such as Accumulated Cyclone Energy (ACE) were far too low,” said Phil Klotzbach, lead author of the forecast at CSU.

The Named Storms:

Arlene – Tropical Storm Apr 19-21 pre-season in Eastern Atlantic

Bret – Tropical Storm Jun 19 – 20 landfall Venezuela

Cindy – Tropical Storm Jun 20 – 23 landfall central Gulf Coast

Don – Tropical Storm Jul 17 – 18 no effects on land

Franklin – Hurricane Cat 1 Aug 7- 10 affecting Yucatan Peninsula and eastern Mexico

Gert – Hurricane Cat 2 Aug 13 – 17 no effects on land

Harvey – Hurricane Cat 4 Aug 17 – Sep 1 Landfall Yucatan and massive flooding in Houston,Texas

Irma – Hurricane Cat 5 Aug 30 – Sep 12 Devastated Leeward Islands, northern Cuba, landfall SE Florida with coast to coast hurricane force wind

Jose – Hurricane Cat 4 Sep 5 – 21 no effects on land

Katia – Hurricane Cat 2 Sep 5 – 9 Landfall eastern Mexico

Lee – Hurricane Cat 3 Sep 15 – 29 no effects on land

Maria – Hurricane Cat 5 Sep 16 – Sep 30 Landfall in Caribbean islands, badly affecting Puerto Rico

Nate – Hurricane Cat 1 Oct 4 – 9 crossed central America and Yucatan

Ophelia – Hurricane Cat 3 Oct 9 – 15 no effects on land

Philippe – Tropical Storm Oct 28 – 29 crossed Cuba and Florida Keys

Rina – Tropical Storm Nov 6 – 9 no effects on land

Expected weak to moderate El Niño conditions, which include increased levels of vertical wind shear preventing hurricane development, did not materialize. Instead, La Niña conditions developed, reducing vertical wind shear. The atmosphere responded to these relatively cool eastern and central tropical Pacific sea surface temperature conditions by generating reduced vertical wind shear in the Atlantic.

The tropical Atlantic was also much warmer than normal during the peak of the hurricane season. Very warm sea surface temperatures and reduced levels of vertical wind shear led to anomalously hurricane-enhancing conditions such Irma, Jose and Maria. While September generated record levels of Atlantic Accumulated Cyclone Energy, all other months of the Atlantic hurricane season had activity at close to normal levels.

With Harvey and Irma making landfall in the continental United States, it is the first time since 1851 that two category-four hurricanes hit the nation in one year.

For detailed discussion of factors contributing to 2017 storm weather, see CSU meteorology (pdf).