Tropical Cyclone Report
12-15 May 2012
14 December 2012
Invest 92L was a highly organized hybrid system of non-tropical origin that formed at an unusually high latitude for the time of year, but did not become a tropical or subtropical cyclone.
Invest 92L originated from a large, extratropical low that formed off the Iberian Peninsula near the Azores Islands on May 10, 2012. The low was attached to a stationary front that extended up to another extratropical low centered over the Norwegian Sea. As the low strengthened, its nearby pressure gradients began to steepen. By the morning hours of May 11, the low had weakened, but had developed its own 1012 mbar closed isobar, with a minimum pressure of 1010 mbar.
Later in the day, convection associated with the low began to wrap around the center, including convection from the attached stationary front and trough. However, the extratropical low remained relatively weak, with a pressure rising to 1016 mbar. This temporary pressure increase would not be long-lasting, however, and throughout the day the low's minimum barometric pressure progressed to fall. By the end of May 11, the low's minimum pressure was 1009 mbar. Throughout May 12, the low continued to strengthen. At 1800 UTC, the low became independent of any associated fronts or troughs, while moving towards the south. Remaining a slow moving system during the afternoon, convection became more condensed around the low level-circulation center, forming organized rainbands and an eye-like feature. At this time, the system was designated as 92L.INVEST. However, its minimum pressure remained at roughly around 1010 mbar, reaching its peak intensity with a minimum pressure of 1009 mbar.
As Invest 92L sluggishly moved aimlessly south of the Azores, overnight its central convection diminished, but 92L still maintained strong convective banding in a ring around its center. Over the course of the day, however, convection continued to become increasingly disorganized and weaker. By the end of May 13, strong convection was primarily confined to the northeastern quadrant and a large rainband to the south of 92L, although it remained an independent system. Despite maintaining a low pressure and rather organized, albeit weak convection, its satellite appearance became somewhat ragged. On May 14, despite reaching its second peak intensity of 1009 mbar, convection became shifted to the northern and southern areas of 92L.
Beginning on May 15, a larger, more intense extratropical system to the north of 92L, centered west of the Azores, began to interact with 92L. At 0000 UTC, a trough of low pressure began to form around a common barycenter between their interaction, and, at 1200 UTC, both individual low pressure areas merged to form a combined 1013 mbar low, south of the Azores.
The 1009-mbar analyzed peak intensity of 92L on May 12 and May 14 is based on oceanwide surface analysis map provided by the Ocean Prediction Center.
There were no ship reports of winds of tropical storm force associated with 92L.
c.Casualty and Damage Statistics
There were no reports of damage or casualties associated with 92L.
1 A digital record of complete surface-analysis maps created by the Ocean Prediction Center for the entirety of the Atlantic Ocean can be found online at http://nomads.ncdc.noaa.gov/ncep/dates.