BATON ROUGE, LA (WAFB) - In the tropics, the National Hurricane Center (NHC) continues to watch Invest 93L in the western Caribbean, with 5-day development chances now down to 40 percent. More importantly, no matter what happens to the disturbance, it does not appear to offer a kind threat to the north-central Gulf Coast.
You might be thinking, "Haven't we already seen Invest 93L already this season?" And you would be correct. In fact, this is "version 3" of 93L for 2017.
Unlike tropical depression "numbers" and tropical storm and hurricane "names," invest identifiers (tags) can be re-used over the course of a single season.
Remember, an "invest" is an "area of investigation," an area of interest.
An "invest" designation does not assert that the NHC forecasters expects the "invest" will become a tropical depression or tropical storm, it merely indicates that the disturbance under investigation has some potential for development. Hence, this week's 93L in the western Caribbean -- the third disturbance of 2017 to be tagged as 93L -- means the NHC has previously labeled 23 areas this season as "invests." That is 24 "invests" so far this season, yet only 15 systems have earned tropical "names."
Keep in mind that in a typical hurricane season, we could see anywhere from 50 to 100 tropical waves in the basin: less than half of those tropical waves even earn "invest" designations, let alone gain a depression "number" or tropical "name."
The practice instituted by the National Hurricane Center and cooperating agencies only uses a range from 90L to 99L for Atlantic Basin "invest" identifiers, cycling through those ten IDs as many times as is necessary over the course of the season. (The same is true for the other hurricane ocean basins as well.)
Why not run from 00L to 99L?
The explanation is a bit convoluted, but suffice it to say that the invest identifiers were never originally intended for "public consumption." For the hurricane forecasting and tracking experts, the 90L to 99L IDs were all that was needed for computer processing as there would never be a time there would be, say, two 91Ls in the basin at the same time.
So what about this season's three 93Ls?
The first 93L was in June and eventually became T.S. Cindy, the first "named" storm to landfall in Louisiana this year.
The season's second 93L eventually became Irma in late August, the first of 2017's two Category 5 monsters.
And what about October's version of 93L? Time will tell, but chances appear low that "version 3" will earn a "number" or a "name."