It’s late July, and there is a good chance that the “I” storm will happen in the next few days, and potentially have impact on the United States (maybe). By the way, there is a video from a meteorologist on Twitter on how to properly pronounce the name Isaías.
The National Hurricane Center began issuing advisories on Potential Tropical Cyclone 9 Tuesday. The open wave is not named yet, but the NHC issues these advisories to give those in the path a “heads up” on the storm’s potential to develop, and allow the issuance of watches and warnings.
The NHC has the cone of uncertainty aiming toward the Florida peninsula for days 4 through 5. But will it really have an impact on The Sunshine State?
First, this writing discuss what is happening as of this post (Tuesday afternoon), and what the variables are.
The wave was looking a little more organized Tuesday afternoon, but the overall circulation appears broad. There appears to be a distinguished “swirl” developing around 12.5°N 57.5° W. Hurricane Hunter reconnaissance aircraft was investigating the disturbance during the construction of this post. The coldest cloud tops were on the northern and western sides of the “swirl”. Regardless, the overall disturbance remains spread out and would need to consolidate to become better organized.
The disturbance was moving westward Tuesday afternoon as it aimed for the Lesser Antilles. Tropical storm warnings were already issued for some of the islands, including the U.S. Virgin Islands and Puerto Rico. Those on the islands should closely monitor the disturbance as gusty winds and heavy rain will be anticipated.
Now for the caveats…
There have been plenty of posts being shared on social media of long-range model guidance on where PTC9/Invest 92L/Future Isaías will go with at least some model guidance aiming it at Florida. But before being sold on guidance there are factors to note.
- The center of the low. Unless there is a center of circulation defined – especially in model guidance – the future path of the storm would be hard to determine. As of this writing, there was no defined center of circulation. It’s like trying to find a starting point on a smartphone map app but the GPS is malfunctioning; therefore, it’s harder to determine the path to get to a destination.
- The weaker the disturbance/system, the more west it will go. This is a general rule of thumb as tropical systems that are not as organized with deep convention tend to follow the general low-level wind flow. This flow is usually from east to west.
- Lack of data. Without a good sampling of the environment in and around the storm, there is not enough quality data to be factored into computer model guidance. It’s the “garbage in, garbage out” mindset. This meteorologist hopes that Tuesday’s reconnaissance flight will start to help fill in the gap.
- Time. With the lack of data and uncertainty of the strength of this system, the path’s room for error increases with time. Remember that the NHC’s cone of uncertainty is based on error over the last five years and NOT associated with an individual storm. (Thanks to Matt Lanza for pointing this out on Twitter)
- The ridge. The ridge of high pressure that normally sits over the Atlantic Ocean will dictate how far west and north it will go. The stronger the ridge, the more west it goes. And the strength can fluctuate during the life of the potential tropical system.
The NHC has weighed in on their discussing reminding everyone that the forecast path depicted on their own map can change.
It cannot be stressed enough that since the system is still in the formative stage, greater than average uncertainty exists regarding both the short-term and longer-term track and intensity forecasts.National Hurricane Center, PTC 9, Discussion 1
If this post is being read by someone in Key West, Miami, Orlando, or Naples, this is what I say: Don’t panic, but keep watching the weather over the next several days. Make sure that your hurricane kit is well stocked and ready to go just in case. With a very active season anticipated, it’s good to be ready.