Tropical Storm Pena Forms With 45 mph Winds Moving Westward

Tropical Storm Pena Forms in the Central Pacific

The National Hurricane Center has initiated advisories on Tropical Storm Pena, a newly organized system in the Central Pacific with sustained winds of 45 mph, or 40 knots. The system developed from Invest CP95, an area of low pressure in the Central Pacific that had been monitored for several days prior to organizing. Satellite imagery showed a well-defined circulation with banded convection around the center, and a 15:46 UTC SMOS microwave pass detected winds above tropical-storm-force east of the center.

Analysts at the Honolulu Forecast Office assigned a constrained subjective Dvorak estimate of 2.0, or 30 knots, but a Data T of 3.0, or 45 knots, which better reflects the system’s organization and matches the microwave data.

Pena Drifts West Under a Central Pacific Ridge

The storm is moving westward at 280 degrees at 10 knots, and forecasters expect that motion to continue for the next several days because a high-pressure ridge centered over the Central Pacific is steering it. Model guidance stays in good agreement on the track through 72 hours, after which cross-track spread increases among the solutions and confidence drops below normal. The weak initial vortex shown in most forecast models adds more uncertainty to predicting the storm’s path. The National Hurricane Center set its track forecast to follow the GDMI and HCCA model aids.

Intensity Forecast Carries Uncertainty

The intensity outlook is harder to pin down. The large-scale environment looks conducive to strengthening for at least the next day or so, with no obvious dry air or instability problems in the guidance, though models show increased shear this weekend that could abate early next week. Many models show little change or even weakening so quickly in seemingly favorable conditions, possibly because they represent Pena’s initial vortex as unrealistically weak. The first official forecast sits on the higher side of the guidance, blending aids that approach hurricane strength with others that weaken the storm to a depression. Like the track forecast, this intensity prediction remains highly uncertain.

More on this story: Disturbance Off Florida Coast Shows Medium Chance of Tropical Development