Invest 96L: Not Looking So Good

Hi everybody, Dr. Rob Carver filling in for Jeff while he is on vacation.

Invest 96L is currently over the Yucatan peninsula and is not looking as impressive as it did over the holiday weekend. Right now, the cloud tops are warming, which indicate that the thunderstorms are weakening. This is likely due to 96L's being ashore right now. Looking into the future, 96L's doesn't show much promise of becoming a significant tropical cyclone. Nearly all of the model guidance has 96L moving in a northwesterly direction along the cool waters churned up in Alex's wake. It looks like 96L will miss the warm SST's at 25N, 87W. It's also expected to move from low shear to higher shear over the the Gulf of Mexico. The ocean offshort of the coastal bend of Texas (Corpus Christi to west of Houston) may allow 96L to intensify if it gets there. There is a small band of warm SST's at the continental shelf, and the wind shear is low (<10 knots).

Looking at the dynamical model output, the story is still murky. Looking at the broad picture, a broad area of 20+ mph winds will affect the Gulf coastline somewhere between Corpus Christi and southeast Louisiana. NAM favors SE Louisiana, while GEM and the parallel GFS favor the coast east of Corpus Christi. HWRF and NOGAPS have the wind affecting the coast west of Houston, while the operational GFS has the wind coming ashore east of Houston. NOGAPS and HWRF are also the only models that show surface winds that are tropical storm force.

I think that that the upper-level circulation and the surface circulation are not strongly coupled together in teh model simulations. This would explain the the discrepancies between the wind swaths I'm describing and the hurricane forecast aids. Those aids use an automatic process to identify the vortex center in the model data that may favor upper-level features for tracking instead of surface features.

To sum it all up, I believe that 96L has a <50 % chance becoming a tropical cyclone before it makes landfall. If it does so, it will likely be near the coast when that happens. In any event though, the winds and waves it generates will likely disrupt oil spill recovery efforts. Also, I would expect a broad area of showers and 20+ mph winds will affect the Gulf coast somewhere from south Texas to Louisiana.


Fig. 1 Plot of maximum winds (mph) over the next 5 days from the 12Z GFS. Parallel GFS wind swath.


Fig. 2 Plot of maximum winds (mph) over the next 5 days from the 12Z NOGAPS. Canadian Global wind swath.


Fig. 3 Plot of maximum winds (mph) over the next 5 days from the 12Z HWRF.


Fig. 4 Plot of maximum winds (mph) over the next 5 days from the 18Z NAM.

Next Update
Tweaks later tonight as necessary, possibly a late night entry describing the Northeast heat wave. Tropical update will be posted Wednesday afternoon.