Fiona Gradually Strengthening Near Puerto Rico, Threat to United States is Low

Lead Forecaster Daniel Crawley

Good Saturday evening to everyone, hope your weekend is off to a good start. We have an update on Tropical Storm Fiona down in the Caribbean.

After dealing with a good bit of wind shear two days ago, Fiona is in a more favorable atmospheric environment as there is a distinct curved arc of convection working from the eastern half of the circulation and wrapping around to the western side of the surface low. You can also see a much better outflow over the top of the storm. That outflow serves as good ventilation for the storm to grow.

Fiona has the potential to become a hurricane over the next 24 hours, the only thing to prevent that would be land interaction with Puerto Rico and Hispanola.

Here is the latest forecast from the National Hurricane Center…the upper level environment should remain supportive for additional intensification as it moves past Puerto Rico/Hispanola and start to move north toward the Southwest Atlantic…Fiona could become a major hurricane by the mid part of next week. The major impacts in the short term will be excessive rainfall for the islands in the Caribbean.

National Hurricane Center Advisory (Sat 5 pm)

Synoptic Forecast…

There is a 500mb ridge to the north of Fiona but it is in the process of breaking down over the next 24 hours. This will allow the storm to reduce its forward motion and turn northwest interacting with landmasses. By the time we get to Monday, Fiona will be exiting to the northwest but due to the weak steering currents the northwest movement will be fairly slow.

500mb height anomalies (Sun 8 pm)

Once we get to the mid-week, there is a sizeable gap between ridging in the Central Atlantic and a Southern US ridge. Fiona could be a major hurricane by this point and with a trough getting ready to dive down into the Eastern US, that should begin to acclerate the storm to the northeast. Bottom Line: These features will keep the United States from seeing any significant impact from Fiona. The storm may increase rip currents but that should be the extent of impacts to the East Coast. The island of Bermuda will need to monitor as Fiona could be in the vicinity…

500mb height anomalies (Wed 8 am)

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