Hurricane Season Likely to Remain Near to Below Average

We have wrapped up two months into the Atlantic hurricane season, but the season is still young. Climatologically speaking, we don’t hit the peak of the season until Sept. 10. So, where are we now and how much could we see for the rest of the season?

SO FAR

There have been two named tropical cyclones in the Atlantic: Arthur and Bertha. Arthur formed off Florida’s east coast as a depression on June 30 and became a tropical storm 12 hours later. Arthur moved north and hit coastal North Carolina on the night of July 3 and took off towards the northeast.

Tropical Storm Bertha formed Thursday night. It currently remains a weaker tropical storm thats entering the Bahamas. Bertha is predicted to remain from the U.S. mainland and head out to sea.

ORIGINALLY PREDICTED…DOZENS OF DAYS AGO…

Academia, government agencies, and private entities have mostly predicted a near average to below average season. To name a few, NOAA predicted eight to 13 named storms, with three to six of those hurricanes and one to two of those major. Doctors Philip  Klotzbach and William Gray of Colorado State University predicted 10 named storms in their June 2 update, with four of those becoming hurricanes and three of those major. WeatherBell predicted eight to 10 named storms, with three to five of those hurricanes and one to two of those major hurricanes.

Many forecasters were thinking that El Niño development could stifle tropical cyclone development in the Atlantic basin. El Niño tends to create higher wind shear in the basin, inhibiting organized thunderstorm development in the tropics. The lower water temps in the Atlantic (cooler AMO index) and drier air were some of the factors considered in WeatherBell’s report.

WHAT NOW?

NOAA is still calling for “weak-to-moderate” El Niño development in the next few months. From the latest sea surface temperature (SST) data, development might be falling off the tracks.

(Source: Climate Prediction Center (CPC)/NOAA)
(Source: Climate Prediction Center (CPC)/NOAA)

Based on the SST anomalies in the equatorial Pacific, development looked promising until mid July as the SST anomalies dropped off the South American coast and rebounded. Though it rebounded, it appears that near-normal temps on the immediate coast have replaced higher SST anomalies earlier in the summer.

So, then I looked at the SST anomalies in terms of the depth below the sea.

(Source: CPC/NOAA)
(Source: CPC/NOAA)

The depth of the warmer waters off the South American coast have decreased since late May.

The El Niño pattern, based on the latest observations, is looking weak at best in the near term. Most dynamical models are still hinting at the continued development of an El Niño event.

(Source: CPC/NOAA)
(Source: CPC/NOAA)

The lack of progression of an El Niño pattern might help keep some life for the rest of the season. Maybe.

There is one factor that has been limiting tropical cyclone development: Dry air.

(Source: CIMSS/University of Wisconsin-Madison)
(Source: CIMSS/University of Wisconsin-Madison)

The map above shows the current Saharan Air Layer (SAL). This dry air, which can also be dusty, can put a choke-hold on tropical cyclone development. TCs aren’t fond of dry air, you see. We experienced a lot of this last year and continue to so far this year.

Gray and Klotzbach released their latest seasonal forecast on Thursday. They are keeping the same numbers as they had in June. They write in their abstract:

We have maintained our below-average seasonal forecast, due to anomalous cooling of sea surface temperatures in the tropical and subtropical eastern Atlantic along with high sea level pressures and strong vertical wind shear across the tropical Atlantic.

The duo also mention the development of a weak El Niño during the peak of the season.

With the dry air and neutral to weak El Niño conditions expected (among other factors), I can expect the rest this season to be near to below normal. However, it’s important to remember that it only takes one storm in one season to affect your location and can have devastating impacts.  Always be prepared.