Invest 96L: Organizing in the Gulf

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

Invest 96L appears to be in the process of developing into a tropical cyclone. The strength and extent of it's thunderstorms is much improved from yesterday (I used CIMMS tropical storm page for my analysis). It's under an upper-level anticyclone which promotes development because it efficiently removes "exhaust" from the thunderstorms. Shear is relatively low (~10 knots), and SST's are adequate for supporting a tropical cyclone (~28 deg. C). In the most recent Tropical Weather Outlook, NHC mentioned that research flights found that upper-level conditions were promising for storm development, so they assess the chances of 96L of becoming a tropical cyclone at 80%. My take is that 96L has an 80% chance of becoming TD #2, and about a 40% chance of being named Bonnie. My reasoning is that 96L has about 24 hours to intensify before interactions with land start interfering with intensification processes. Also, model intensity forecasts are not very supportive of 96L attaining tropical storm force winds. The model track forecast aids have 96L's center of circulation making landfall somewhere between Brownsville and Corpus Christi.

Impacts
The 12Z operational GFS, HWRF, NOGAPS, and 18Z NAM tell a similar story about the surface winds. Near tropical-storm force winds affect the Texas coast from Corpus Christi to Matagorda Bay. A broad area of 30+ mph winds also affects the Deepwater Horizon oil spill recovery efforts. The 12Z Canadian global model downplays the wind strengths, and the 12Z parallel GFS fails to develop any significant surface wind (> 20 mph). That said, I believe that 96L's greatest impact will be in the form of rain.

The Rio Grande from Del Rio to Laredo is either at major flood stage or is forecast to reach major flood stage in the next 24 hours. This is due to Alex and the moisture he brought to the high terrain of northern Mexico. Nearly all of the forecast models I've looked at forecast 2-3 inches of rain over the Rio Grande Valley in the next 5 days. That will only encourage more flooding. The main forecast problem is how much rain will fall along the Gulf Coast. The parallel GFS and HWRF suggest that 4.5 to 6.5 inches of rain will fall in the Galveston/Houston area in the next 5 days. In my opinion, people living in this area should be prepared for flooding.


Fig. 1. 120 hr accumulated precipitation (mm) for 12Z parallel GFS. Operational GFS


Fig. 2. 120 hr accumulated precipitation (mm) for 12Z HWRF.


Fig. 3. 120 hr accumulated precipitation (mm) for 12Z Canadian global model. NOGAPS

Emergency Preparations
People living along the Gulf coast from south of the Rio Grande to the Texas/Louisiana border should review their emergency preparations (hurricane preparations also make for good flood preparations). Jeff has put together a guide to hurricane preparedness with plenty of links for more information.

Next Update
If 96L becomes TD2 or Bonnie, I'll have an update tonight. Shaun Tanner may post something in the morning if that's when the naming occurs. Otherwise, I'll post a tropical update tomorrow afternoon.