Tropical Storm Cristobal is on the move, on a due north track. More or less on schedule, the dip in the jet stream setting up over the western Gulf scooped up Cristobal and the large mass of rotating moisture around it and propelled them north.
The center of the tropical storm should arrive at the Louisiana coast midday tomorrow, but the bad weather will arrive on much of the Gulf Coast long before that. Heavy rain with gusty winds will likely reach the Florida Panhandle tonight.
In addition, the Gulf water will rise along the coast from Louisiana eastward starting today. High tide comes in the late morning. The tide change will account for about a 2-foot swing in the water level.
The National Hurricane Center is predicting that the water could reach 3 to 5 feet about normal high tide along the eastern Louisiana and Mississippi coast up to about Biloxi. Storm surge alerts reach all the way across the Florida Panhandle almost to Tampa Bay. On the NHC’s storm-surge forecast map, you can see where the most vulnerable areas are.
The atmospheric conditions across the Gulf do not appear conducive for dramatic strengthening. Upper-level winds are not especially favorable, and there is a lot of dry air wrapping into the system. Cristobal is not a classic tropical storm in shape. It looks more like a comma. The offshoot of that is that the bad weather will arrive at the coast earlier, and stay longer to the east of the track.
And Cristobal’s circulation is quite large, thanks to the so-called Central American Gyre, which enveloped the tropical system from the beginning. Now the circulations have merged, resulting in the new version of Cristobal having a large diameter.
The upper-level winds are situated such that most of the bad weather will be on the Florida side – the east side – of the storm track. With many tropical systems, and especially these lopsided storms, a tail of intense tropical moisture develops well behind and to the right of the storm track. The questions for South Florida are, where will that tail set up and how strong will it be.
The latest forecasts show Cristobal consolidating enough to keep the most intense part of the tail over the Gulf, but part of the moisture flow will be over the Florida peninsula into next week. It will just maintain the extremely humid air mass we’ve had this month. With the storm moving north, the rain chances will not be as high, but when we get a downpour, it could be quite heavy with the tropical moisture in place.
About Wednesday night or Thursday, the computer forecast models show a front with drier air behind it pushing in off the Atlantic. If that works out – as unusual as it is – the air should feel fresh for a moment. It won’t last long.
Nothing is showing up in the tropics behind Cristobal, so hopefully things will stay calm, and we’ll get a break for a while.