The 2017 Atlantic hurricane season is not over yet. A non-tropical area of low pressure located over the central subtropical Atlantic acquired a well-defined circulation and persistent deep convection, resulting in the initiation of advisories on Tropical Depression Nineteen early this morning. The depression is no threat to land, and is likely to strengthen into Tropical Storm Rina later today or on Tuesday as it moves north-northeastward through a marginally favorable environment. If Nineteen does become named Rina, 2017 will become only the sixth Atlantic hurricane season (joining 1995, 2005, 2010, 2011 and 2012) to feature a named storm starting with the letter R. In addition, Nineteen’s formation makes 2017 the first Atlantic hurricane season since 2013 to feature a tropical cyclone form in every month of the season (June through November). Tropical cyclones forming in the Atlantic during the month of November are not that uncommon – on average, a named storm forms in the month about every 6 out of 10 years, with a hurricane forming about every 3-4 out of 10 years.
As of 10:00 a.m. EST Monday, Tropical Depression Nineteen was centered near 29.5°N 50.4°W, and was moving north-northeastward at about 3 mph. Maximum sustained winds were 30 knots (35 mph), with an estimated minimum pressure of 1013 mb. The depression currently is sheared, with the center of circulation partially exposed to the northwest of the main convective mass. Although conditions are only marginally favorable for tropical cyclone development, with sea surface temperatures of about 25-26°C (77-78.8°F) and wind shear a moderate 15-20 knots, unusually cold upper-level temperatures and baroclinic processes should help the depression strengthen into Tropical Storm Rina. Most of the intensity guidance predicts that Nineteen will peak as a moderate to strong tropical storm. It appears unlikely that the depression will become a hurricane, but this scenario cannot be ruled out completely. Nineteen should merge with a cold front and transition into an extratropical cyclone by late Wednesday, when it enters very cool waters and very strong wind shear. It is possible that the extratropical remnants of the depression could reach the United Kingdom as a weak extratropical cyclone, though this remains uncertain.
I will be back with an update on Tropical Depression Nineteen tomorrow, which is likely to be Tropical Storm Rina by that time.