Daily Archives: Saturday, May 19th, 2012
13 days early, but Hurricane Season 2012 is here with the entrance of Tropical Storm Alberto off the Carolina coast. Despite two attempts to get a few personal things done around the house today, Alberto decided to develop precisely in sync with those activities, but nonetheless Alberto continues to develop this evening. Alberto is a rather small system with tropical storm force winds only reaching out 45 miles from the core and maximum sustained winds at 60 mph. I think that these winds might be just a tad too high based on the amount of dry air surrounding this system and the probability of a downburst. That being said, WINDSAT did come in a couple of hours ago with uncontaminated 60kt wind vectors close to the storm, but I’m not sure how reliable these are. Based on the earlier ship report and the windsat reading, 60 mph is probably a good blend. Being such a small system may actually help Alberto survive over the next couple of days, but we’ll get to that in a bit. He is a rather tilted and lopsided system in that the radar presentation seen below and the low-level center seem to be dislocated by a good distance, and I expect this to continue throughout the lifetime of Alberto. Alberto’s minimum pressure as indicated in part a ship that caused a 6pm update by the NHC is 995 millibars. I chose the radar presentation from Charleston rather than from Wilmington in part due to the weaker reflectivity region ESE of downtown Charleston. I figure the center is likely well south of that, but it’s an interesting spot to watch for possible relocation.
Alberto’s rather small envelope will help him stay away from the large amount of continental dry air that is lurking just to the north and west of the center of circulation. Dew points pictured below (time = 7:40pm ET) are ranging from 40-50 degrees Fahrenheit over North Carolina. An extratropical low pressure system to the northeast of Alberto is flinging dry air to the south, which may impede any intensification of Alberto as well as keep coastal locations a bit drier than would be otherwise. Wind shear, which takes off the tops of tropical systems, is generally low and is becoming more favorable for development. I’m not expecting excessive rainfall for the Carolinas with the exception of possible Cape Hatteras as Alberto moves through.
The computer models seem to be having some difficulty locating Alberto due to its rather small size, but most have Alberto meandering to the south and west over the next day. At some point during the evening of Sunday, an upper level trough is expected to move into the eastern United States, which will pick Alberto up and put it on a northeasterly trajectory, but there really is no model consensus with when and exactly where this turn may take place. In terms of Florida, a few of the ensemble members of various models do bring Alberto down as far south as the Jacksonville latitude, but until an operational model shows this I am expecting a clockwise turn to the north somewhere off the Georgia coast tomorrow night. It remains to see exactly how close Alberto will get to the coastline, and if Alberto will get to the North Carolina coast on the way out. I’ll look at that tomorrow afternoon. Alberto does have about a 36 hour window for some intensification, and I believe Alberto could get as strong as a 65 mph tropical storm barring any surprise collapses over night from dry air or sudden convective bursts. I would watch for an early morning slow intensification with the heating of the day. As of right now no tropical storm watches are in effect for any coastal locations, but NHC did mention they may issue new advisories for these locations later tonight or tomorrow.
It does look like there will be a recon flight tomorrow into Alberto, but when I am not sure at this point.
**Special Notes from the NHC: Alberto and the east pacific’s Aletta make up the only team of tropical cyclones to both form before the beginning of their respective hurricane seasons! In fact, the Atlantic is ahead of schedule by 34 days. This does not mean that the Atlantic Hurricane Season will be more active than normal, but it does mean that you should get your hurricane kits together.
I did not want to forget our little friend off the coast of Belize, but it looks like wind shear from the subtropical jet got the best of 92L. There is no discernible circulation, but the area remains convectively active and at least a couple of the model show a batch of moisture moving toward the north over Cuba and toward Florida on Tuesday and Wednesday. For now, this will be the last mention as 92L has been deactivated.
Eye on Florida
With a tropical storm to the northeast and a tropical low to the south, where does this leave Florida? DRY…with the exception of south Florida. All of that dry air in the Carolinas will make it into Florida tomorrow from north to south, which will pin most of the moisture and thunderstorms to the south of a line from Fort Myers to Lake Okeechobee. Winds will stay out of the north with the exception of the sea breeze, which will still push through each day. Dew points, and overall mugginess will a bit lower than what we would expect this time of year due to the dry air conveyor belt coming in from the north. Dew points in the eastern panhandle and northeast Florida (pending the distance of Alberto) may fall as low as the upper 40s and low 50s during the day on Sunday and into Monday. There may be a moisture return from south to north over south and central Florida on Wednesday and Thursday as the low over the western Caribbean gets dragged north.