The 2017 Atlantic Hurricane Season is in full swing. According to climatology, this time of year typically sees the most tropical cyclone activity. The combination of a peak in sea surface temperatures, minimum in vertical wind shear, and a reduction in the extent of the dry and stable Saharan Air Layer this time of year all factor into why it is often very active.
This morning, Irma continued to strengthen. Near-continuous aircraft missions into the hurricane have found that maximum sustained winds have increased to near 185mph, making Irma a category 5 hurricane on the Saffir-Simpson Hurricane Wind Scale and capable of catastrophic wind damage where the core of the hurricane comes ashore.
Short Term Forecast: Hurricane Irma is now beginning to turn toward the west-northwest as it tracks around the south side of the deep-layered Bermuda-Azores high. On this track, Irma will pass very near or over several of the Leeward Islands and Puerto Rico where Hurricane Warnings are in effect.
Potentially catastrophic wind damage is possible should the core of Irma’s strongest winds come ashore on any of these islands. However, as hurricane force winds extend up to 60 nautical miles from the center, widespread damaging winds can be expected through the Leeward Islands. Heavy rain could result in life threatening inland flooding, and a significant storm surge is expected to cause dangerous coastal flooding.
Irma is expected to remain in a very favorable environment with high ocean heat content, low vertical wind shear, and away from mid-level dry air. Irma is therefore expected to remain a very powerful hurricane with intensity mostly being controlled by internal storm structure as it approaches Antigua and Barbuda tonight. Irma will spend most of Wednesday passing through the Leeward Islands and should begin to pull away by Wednesday night.
Hazardous swell from Irma is forecast to reach Bermuda’s southern marine area on Thursday, with 6-10ft seas outside the reef. Otherwise Irma will pass more than 800 miles south of the island during this time.
Tropical Storm Jose
Over the central Tropical Atlantic, satellite wind measurements have indicated that a tropical disturbance has organized into a tropical storm with maximum sustained winds near 40 mph winds, becoming Tropical Storm Jose.
Short Term Forecast: Jose is pulling west-northwestward out of the central Atlantic, feeling the same steering flow as Irma. The storm is in a mostly favorable environment and a general strengthening trend is expected. However, upper level outflow from Irma could introduce periods of strong vertical wind shear that could hinder strengthening at times. Jose is not a threat to land at this time, but could become a threat to the Leeward Islands over the weekend.