Dr. Jeff Masters' WunderBlog

Alberto weakens, brings light rains to Georgia and South Carolina

Posted by: JeffMasters, 3:31 PM GMT on May 20, 2012

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Tropical Storm Alberto continues to move slowly to the west-southwest off the coast of South Carolina, and is bringing light rains to the coasts northern Georgia and southern South Carolina. Recent radar and satellite loops show that Alberto has weakened late this morning, and has lost most of its heavy thunderstorms. Upper level winds out of the west-southwest are creating a moderate 15 - 20 knots of wind shear over Alberto, and these winds are driving dry air into the storm, which has caused it to deteriorate. The dry air impinging on Alberto can be seen in water vapor satellite loops. Yesterday, Alberto was over the warm 81°F (27°C) water of the Gulf Stream, but today, the storm has moved west of the Gulf Stream, and is now centered over cooler waters of 79°F (26°C). This gives the storm a lot less energy to power it, and as Alberto drifts farther to the west-southwest today, ocean temperatures will get even cooler. A hurricane hunter aircraft is scheduled to visit Alberto this afternoon.

Figure 1. Late morning visible satellite image of Alberto.

Forecast for Alberto
Sporadic rain showers from Alberto are likely to affect the Georgia and South Carolina coasts today, and the coasts of North Carolina and South Carolina on Monday. The heaviest rains and tropical storm-force winds should remain offshore, but even if Alberto did make landfall, the storm is too small to cause major flooding problems, particularly since the coast is under moderate to severe drought. Alberto's rains will be generally less than an inch over land areas, which will not be plentiful enough to cause significant drought relief. Wind shear is expected to increase to the high range, 30 - 40 knots, tonight through Monday, which should be able to rapidly disrupt a storm as small as Alberto. Steering currents are weak, and Alberto will wander off the coast of South Carolina through Monday morning, before getting caught up by a trough of low pressure on Monday night which should lift the storm out to the northeast. NHC is giving Alberto a less than 5% chance of reaching hurricane strength. Alberto should cause little or no damage to the coast, except perhaps for some coastal erosion due to high waves.

Figure 2. Late morning total rainfall image of Alberto from the Charleston, SC radar. Alberto's rains have been less than one inch along the coast, and most of the rain has fallen offshore.

Figure 3. Late morning radar image of Alberto from the Charleston, SC radar.

Alberto in historical context
Alberto is earliest-forming tropical storm in the Atlantic Basin since Ana in 2003, which formed on April 21. Alberto is one of only three Atlantic tropical storms to form in May in the past 31 years. The others were Tropical Storm Arthur of 2008, and Tropical Storm Arlene of 1981. There was also a subtropical storm, Andrea, that formed in May of 2007. Formation of an early season tropical storm from an old frontal boundary, like occurred with Alberto, is not a harbinger of an active hurricane season--it's more of a random occurrence. Early season storms that form in the Caribbean, though, often signal that a busy hurricane season may occur.

I'll have an update Monday morning.

Jeff Masters

Categories:Hurricane

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Tropical Storm Alberto forms off the South Carolina coast

Posted by: JeffMasters, 9:41 PM GMT on May 19, 2012

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The first named storm of the 2012 Atlantic hurricane season is here. Tropical Storm Alberto formed this afternoon off the coast of South Carolina--a little going-away present for outgoing NHC director Bill Read, who retires on June 1! Alberto has the potential to hit North Carolina as early as Monday, but since the storm is so small, it would only affect a small area of the coast with high winds and heavy rain. Upper level winds out of the southwest are creating a m...

Categories:Hurricane

Updated: 10:29 PM GMT on May 19, 2012

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Disturbance 93L off South Carolina coast could become a tropical storm

Posted by: JeffMasters, 5:11 PM GMT on May 19, 2012

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A hybrid low pressure system with both tropical and extratropical characteristics has formed in the waters off the coast of South Carolina, about 120 miles southeast of Myrtle Beach--a little going-away present for outgoing NHC director Bill Read, who retires on June 1! Residents along the South Carolina and North Carolina coast should pay attention to 93L, as it has the potential to strengthen into a tropical storm and hit the coast on Sunday or Monday, with North ...

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April 2012: Earth's 5th warmest on record

Posted by: JeffMasters, 12:00 PM GMT on May 18, 2012

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April 2012 was the globe's 5th warmest April on record, according to the National Oceanic and Atmospheric Administration's National Climatic Data Center (NCDC). NASA rated April 2012 as the 4th warmest April on record. April 2012 global land temperatures were the 2nd warmest on record, and the Northern Hemisphere land surface temperature was 1.74°C (3.13°F) above the 20th century average, marking the warmest April since records began in 1880. Global ocean temperat...

Categories:Climate Summaries

Updated: 8:51 PM GMT on May 18, 2012

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The Hockey Stick and the Climate Wars: a book review

Posted by: JeffMasters, 12:48 PM GMT on May 16, 2012

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No climate scientist has been subject to more attacks on their science and character than Penn State's Michael Mann, originator of the famed "hockey stick" graph of Earth's temperature history. Dr. Mann has an excellent new book called "The Hockey Stick and the Climate Wars: Dispatches from the Front Lines" that takes the reader on a fascinating journey to the front lines the high-stakes battles between climate scientists and their detractors. It's a must-read for e...

Categories:Book and Movie Reviews Climate Change

Updated: 12:52 PM GMT on May 16, 2012

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