Tropical Storm Rina Forms in Central Atlantic

The 17th named storm of this hyperactive Atlantic season, Tropical Storm Rina, was christened by the NOAA/NWS National Hurricane Center at 10 pm EDT Monday. Fortunately, Rina will pose no threat to land. Located roughly 900 miles east of Bermuda, Rina was moving slowly north across the Central Atlantic with top sustained winds of 40 mph, the minimum needed to qualify as a tropical storm. Rina’s upgrade was based mainly on data from the ASCAT scatterometer, which showed winds of up to 35 knots (40 mph) east of the center.

Rina’s ascent to tropical storm status is a true accomplishment given its less-than-intense showers and thunderstorms (convection) and the strong westerly wind shear plaguing the storm (20 - 25 knots). The shear was pushing virtually all of Rina’s convection east of the storm’s exposed low-level center.

Rina is moving over waters of 26°C (79°F), about 0.5°C above average. This is ordinarily only marginally warm enough to support a tropical storm. However, temperatures in the upper atmosphere over Rina are about 2°C below average, making the difference in temperature between the surface and upper atmosphere large enough to create the instability needed for development of a tropical storm. This is the same combination of surface- and upper-level ingredients that allowed Category 3 Hurricane Lee to form in the same general area in late September--though Rina is not expected to reach hurricane strength.

Figure 1.  NHC’s wind probability forecast for Tropical Storm Rina issued at 7 pm EST Monday evening, November 6, 2017, kept Rina’s strong winds out to sea for the duration of the storm’s life. Image credit: NHC.

Based on intensity models, Rina has a chance of some modest strengthening over the next couple of days, as it heads northward at a gradually increasing clip over progressively cooler sea-surface temperatures but a somewhat moister atmosphere. Later this week, Rina will become caught up in stronger mid-latitude flow and should quickly lose its tropical characteristics as it races northeastward, avoiding land.

Will Rina become the first “R” storm to fall short of hurricane status?

According to Dr. Phil Klotzbach (Colorado State University), 2017 joins a select group of only seven other years since 1851 that have seen a total of 17 named storms in the Atlantic by November 6. The other years are 1933, 1969, 1995, 2005, 2010, 2011, and 2012. Each of those years went on to generate at least one additional storm. According to Cat 6 reader HurricaneFan, all five of the previous “R” storms in the Atlantic (going back to the start of official naming in the early 1950s) were hurricanes. These included Roxanne (Cat 3, 1995), Rita (Cat 5, 2005), Richard (Cat 2, 2010), Rina (Cat 3, 2011), and Rafael (Cat 1, 2012). This year's Rina is also the first "R" storm to develop as late as November.

We’ll be back with our next update by midday Tuesday.

Dr. Jeff Masters contributed to this post.