Here is the 7 a.m. CDT update from the NHC on Cristobal. A few notes on the forecast are below for those that are interested as well as a note on the possibility for severe weather tomorrow in northern AL and TN.
The NHC is showing a tropical storm impact to Louisiana early next week and that is the most likely scenario but there is still some uncertainty. The NHC cone captures the range of track possibilities well so I won't go into that. I will say that Levi Cowan (TropicalTidbits) mentioned last night that timing could vary by as much as 24 hours. Where the storm ends up in the current cone has to do with timing as well as the storm's strength and other factors that cause normal forecast variability.
Here are a few comments on what is causing the uncertainty and how that may affect the forecast. At some point tomorrow and through the weekend steering influences will start to pull weather from the southern Gulf northward. What this "weather" is depends on how far inland Cristobal goes over Mexico today and tomorrow. Some models have been consistently showing Cristobal going far enough inland to completely dissipate. What they then show is the whole monsoon gyre over southern Mexico and Central America being pulled north on Friday and Saturday potentially spawning another system over the open Gulf. If this were to happen and another full-fledged tropical cyclone were to form it would probably be named Dolly. I won't go into too much detail but both the GFS and ECMWF show this occurring to different degrees with the GFS showing complete dissipation and the Euro keeping Cristobal relatively intact. The GFS and ECMWF ensemble models (GEFS and EPS) show a range of possibilities from Cristobal staying completely offshore before being pulled north to completely dissipating over Mexico. It seems like some kind of interaction with land that will weaken the storm, but not cause dissipation, is most likely and this is what the NHC is forecasting with the official track just inland enough to weaken Cristobal to a tropical depression before it reenters the Gulf.
The degree of land interaction will influence the intensity of the storm as it moves north. Conditions are favorable for intensification right now but will become more hostile over the next few days due to increasing wind shear and dry air intrusion. If Cristobal weakens a lot over land then it won't strengthen as much when it crosses the Gulf and vice versa. So we could be looking at anything from a rainy messy system without a name to a category 1 hurricane. Right now a tropical storm looks most likely and this is what the NHC forecast shows.
Severe Weather Possibility Tomorrow
Turning to severe weather, there is a marginal chance (1 on a scale of 1 to 5) of severe weather tomorrow for northern Alabama and Tennessee. Damaging wind and hail are the main threats, with the hail threat being only in Tennessee. Timing looks to be in the afternoon
That's all I have today. I don't think we're looking at a major event from Cristobal but it's something to keep an eye on. Have a great rest of the week.
Chris
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