A very strange meteorological occurrence happened over the weekend, with an extratropical storm named Ophelia reaching far northeast as Ireland. The event was so unusual that the software used in mapping tropical storm winds was not compatible with the location, thus cutting the wind speed map of the storm abruptly.
The National Hurricane Center program that shows wind speed probabilities used boundaries based on where storms from the past decades had hit. No storm was ever recorded to go as farther north than 60 degrees latitude, or farther to the east as zero degrees longitude. That is why locations beyond these markers are not included in the software.
According to Michael Brennan, a hurricane specialist at the NHC, the limits to the map was an acceptable tradeoff for a faster system. "The larger the grid, the longer it takes to run the computation, so it's a tradeoff," he said.
The NHC eventually tweaked the code to include the full wind speed probability for the storm. "In hindsight, in figuring out what domain to use, we probably should have left a little bit of room to take into account the size of the storm," said Mark DeMaria, acting deputy director of the NHC.
The storm Ophelia, became a Category 3 Hurricane earlier in the weekend. It was the easternmost Category 3 Atlantic hurricane ever recorded. The storm was downgraded to a post-tropical storm by the time it reached Ireland. However, this marked the very first severe weather alert for the entire country.
Having a storm this strong at the far north is a very rare occurrence because the water on the ocean surface gets colder in higher latitudes, and storms need warm ocean water to fuel its strength. However, it turns out that this year, the overall temperature of the Atlantic Ocean was warmer than usual, thus allowing the storm to maintain its strength even as it moved to northern regions.
