Hurricane Erin has weakened a bit, slowed, and is well in to the northward turn just off the Bahamas this morning. As noted in the National Hurricane Center’s Key messages regarding Hurricane Erin (en Español: Mensajes Claves), the thing that is different is Erin’s increasing size.
First, here is the 5am forecast track, along with watches and warnings:
Here is the forecast track using my TAOS(tm) TC model, which has a “large storm” wind model for cases like Erin. Notice how much bigger the wind field is with the latest forecasts:
There are a lot of complex reasons that control the size of a storm, mostly due to the surrounding environment. Hurricanes can have a very wide range of sizes, even for very intense storms. The radius of hurricane force winds for a Category 3 storm can range from just a few miles across to over 100 miles, with an average of 50 miles or so. The range of tropical storm force winds from a Category 3 can have an even larger variation, from 50 to 500 or more miles for storms at more northern latitudes. Erin’s radius of tropical storm force winds is forecast to reach 340 miles in about three days.
Taking a wider view with the latest outlook, we also see two disturbances coming off the coast of Africa. The first (#1 on the NHC TWO) is pretty disorganized and while it has potential is not an Invest yet. The second is more organized and has an invest number (AL99).
As a side note, you may have noticed I am experimenting with some different mapping tools that are easier to automate and bring in outside data than Google Earth Pro (which I’ve used for a long time and really like, but it’s harder to automate). Let me know what you think.
Tracking for Erin continues to be tight. Here are the currently available tracking models. Notice these maps are also including early trajectory model forecast for AL99. Remember that track models for disturbances – especially systems like AL99 that don’t even have a center of circulation yet, are highly uncertain and really only a general idea of the direction of motion. On some of the maps you will see a bright green line. That is the Trajectory CLIPER model, which is a statistical/climatalogical model that shows how storms at that location and motion have traveled, and gives an indication of how different (or not) this storm is likely to be vs. history.
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New maps are fine. Make it easy for you. The information is very helpful. Thanks