I'm a CMU Honors student and love meteorology and extreme weather. I've been fascinated by weather since I was 5, and plan on becoming a meteorologist
By: wxchaser97 , 3:53 AM GMT on November 30, 2012
My first TCR(Tropical Cyclone Report) of the 2012 Hurricane season and just my first TCR ever wrote. They aren't official NHC TCR's but I try to make them the most accurate as possible. The next TCR will be on Beryl and hopefully released by the end of Sunday night. I will continue to try my best to provide accurate reports on the Atlantic tropical cyclones and I will write a TCR for every Atlantic storm this season.
Tropical Cyclone Report
Tropical Storm Alberto
May 19th-May 22nd
Thursday, November 29, 2012
Alberto was an early forming tropical storm that skirted the southeastern United States coastline.
a. Synoptic history
Alberto formed from a non-tropical low that was associated with a mid to upper level trough. A low was first noticed in the second week of May. A cold front and low pressure system moved into the gulf around the 12th of May. This low slowly started to break away from this front as it moved northeast. Associated precipitation and cloudiness came with it, but everything was disorganized. Part of the disturbance stalled off the Southeast coast of the United States while the other part continued northeast. By the 18th a new low, a surface low this time, was developing and building convection based off of satellite and Doppler radar. This low started to get tracked by the National Hurricane Center (NHC) on May 19th when it was 120 miles to the southeast of the South Carolina coast. This low would acquire tropical characteristics throughout the day as a closed surface circulation became present and convection became deep and sustained. An Advanced Scatterometer (ASCAT) pass showed 40kt winds and a closed circulation, see figure 2. This low was tagged as an invest due to its potential for development. The structure of this system had become better defined at this point and a tropical cyclone was likely to form. The environment around invest 91L was marginally favorable for tropical cyclone development. While shear was low and instability was above normal, ocean temperatures (SST’s) weren’t what they would be in August/September. The water was warm though, enough for tropical cyclone genesis. On May 19th at 2100 UTC, the area of low pressure became Tropical Storm Alberto.
Alberto would then slowly drift to the southwest over the next day. The tropical storm was located in an area with little steering influence. As a trough began to move near Alberto he turned to the east and then northeast. Alberto hit peak intensity very early in his life, courtesy of a ship report nearby, see figure 1. At 2250 UTC on May 19th, Alberto reached a peak intensity of 50kts from the special advisory put out by the NHC. This is also when Alberto looked his best, which wasn’t that good, structure wise as he would be soon overcome by multiple environmental factors. After the 19th, dry air and southwesterly wind shear worked hand in hand to weaken Alberto. While he was right near the Gulf Stream, the shear was too strong and the dry air was too abundant for the Gulf Stream to have a big effect on Alberto. Over the next couple days Alberto continued to weaken mainly due to dry air and wind shear. Convection decreased and the circulation became less defined as he turned to the northeast. The circulation became exposed despite attempts from Alberto trying to re-fire convection. On May 21st at 2100 UTC, Alberto was downgraded to a tropical depression and he barely was even able to be classified as one. There was very little convection and the circulation was becoming elongated as the trough was picking him up. On May 22nd at 1500 UTC, Alberto lost all tropical characteristics, became a remnant low, and was expected to fully dissipate in a couple of days. As the remnants of Alberto continued to move northeast, they got absorbed into a trough.
b. Meteorological Statistics
Observations to determine Alberto’s strength include Advanced Dvorak Technique satellite estimates, University of Wisconsin's-Cooperative Institute for Meteorological Satellite Studies analysis maps, NWS radars, NOAA Hurricane Hunters, Advanced Scatterometer (ASCAT) passes, microwave data, and ship/ buoy reports were all used in the forecasting and tracking of Alberto.
The 50kt peak for Alberto was recorded from a ship that clocked 50kt winds and had a pressure of 995mb. Other ships and buoys would report tropical storm force winds along with ASCAT data showing sustained tropical storm force winds. Before Alberto became a tropical storm, his precursor produced rain and gusty winds over North and South Carolina. While there were no 35kt+ winds recorded, gusty winds caused some nescience for the area along with some rain. Winds would increase once he got offshore and Alberto skipped the depression stage. It is also interesting to note that Alberto merged into the same trough that would go on to form Beryl a few days later. Alberto was the earliest forming tropical storm since Ana of 2003 and was the first named storm to form in May since Arthur of 2008.
c. Casualty and Damage Statistics
No deaths or damage occurred with Alberto since he stayed off the United States coastline.
d. Forecast Verification
The formation of Tropical Storm Alberto was generally not expected to happen. There wasn’t a mention in the Tropical Outlook until the day of formation. This was due to a fast transition from non-tropical to fully tropical, a matter of hours. The National Hurricane Center never really had the opportunity to give much mention well in advanced. There also wasn’t a great consensus on whether a storm would form and, if one did, where it would form. Model runs had a storm/low forming in all parts of the Atlantic and at different intensities. This made it difficult for the NHC to pinpoint where tropical cyclone genesis would occur. They did have some of a handle about 24-12hrs before formation occurred.
Intensity forecasts were pretty good for Alberto from the get go. Besides the early spike in intensity, the NHC was pretty well spot on.
The track forecasts were less accurate during the earlier part of Alberto’s life. The NHC had forecast Alberto to move inland or very close to it. Alberto stayed farter offshore than originally thought but forecasts improved as he got closer to his death. Tropical Storm Watches were issued for the South Carolina coast but they were dropped not too long after as it became likely Alberto would remain out to sea. Since he stayed farther offshore, not much more than higher waves were felt along the coast.
Figure 1. Alberto at peak intensity of 50kts.
Figure 2. ASCAT image of Alberto on May 19th showing a well defined circulation and tropical storm force winds.
Figure 3. My past track image of Alberto.
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