Dora Becomes the Year’s First Western Hemisphere Hurricane

After a burst of intensification that took hold on Sunday, Hurricane Dora was prowling the open waters of the Northeast Pacific on Monday. Dora is the first hurricane-strength storm to develop in the Western Hemisphere in 2017, following three named storms in the Atlantic and three in the East Pacific. Dora is also the first hurricane to be tracked by the new high-resolution GOES-16 satellite, the first in the next-generation GOES sequence.

As of 11:00 am EDT Monday, Dora was located about 175 miles southwest of Manzanillo, Mexico, according to the NWS/NOAA National Hurricane Center (NHC). Dora was packing sustained winds of 75 knots (85 mph), making it a solid Category 1 hurricane. Dora reached hurricane strength early Monday, taking advantage of sufficiently warm sea surface temperatures (SSTs) of around 27°C (81°F) combined with very low wind shear (less than 5 knots) and a moist middle atmosphere (relative humidity above 70%).
 

Figure 1. WU depiction of NHC forecast for Hurricane Dora as of 11:00 am EDT Monday, June 26, 2017.

Outlook for Dora

Dora is moving northwest, parallel to the Mexican coast, and that motion is predicted to continue with a gradual arc toward the west. This movement will keep it offshore and no threat to land, apart from a few heavy rain bands on Monday along the immediate Mexican coast.

Dora’s days as a hurricane are numbered because it is quickly moving toward cooler waters. By early Tuesday, Dora will be passing over SSTs below the benchmark 26°C level for tropical cyclone development. Wind shear will remain quite low, so Dora may take its time spinning down. NHC’s forecast on Monday morning called for Dora to dip below hurricane strength by Tuesday afternoon. Around that point, it will pass near or over Socorro Island, which hosts a Mexican naval station and several dozen permanent residents. Dora’s weakening will allow the low-level trade winds to take an increasing role in steering the system, thus producing the expected westward arc.

Finally, a hurricane—but it’s not all that late for it

According to climatology, the first hurricane of the Eastern Pacific hurricane season typically arrives on June 26, so we are exactly on schedule for that statistic. However, the fourth named storm of the year typically does not arrive until July 14, so we are ahead of the usual pace for named storms.

Although we made it almost halfway through 2017 before notching our first hurricane in the Western Hemisphere, that’s not so unusual. According to expert Dr. Phil Klotzbach (Colorado State University), the last time we went this long without a hurricane in the Atlantic or Northeast Pacific was 2008, which saw Hurricane Boris develop in the Pacific on July 1 and Hurricane Bertha in the Atlantic on July 7.

Ten other years since 1971 saw their first Atlantic or Northeast Pacific hurricane after June 25.  In some of those years, though, we had already seen a hurricane-strength system east of the International Date Line in the Western Pacific.

The long-range Atlantic outlook

A strong tropical wave that will be coming off Africa later this week bears watching. It is far too soon to know if or how this wave might develop as a tropical cyclone, but the GFS ensemble system provides some support for the idea of this impulse intensifying over the western tropical Atlantic a little over a week from now. Although this region becomes slightly more favorable for development in July, only a handful of tropical cyclones have formed east of the Antilles during early and mid-July in records going back to 1851.

Jeff Masters contributed to this post.