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Earl nails Nova Scotia;Gaston not gone

Posted by Andy Johnson under Daily updates

 Earl was downgraded to a tropical storm at 11PM EDT, Friday, September 3, 2010. Due to Earl’s asymmetrical wind field, Cape Cod and Maine were largely spared strong winds. In fact, there were no land stations in New England that reported sustained gale force winds. As I had mentioned in my blog earlier this week, the effects of Earl were likely to be much greater on its eastern side. Part of the reason for this, is that Earl was moving at a rapid forward speed while passing to the east of Cape Cod. Winds rotated counterclockwise around a hurricane in the northern hemisphere. In addition, to the rotational wind, there is also the forward movement of the entire circulation of the storm. Earl was moving as fast as 40 MPH by Saturday afternoon. So, the winds on the right side are the sum of the rotational speed and the forward speed and on the left side the forward speed is subtracted. This can be seen graphically in the images below from the Hurricane Research Division of NHC.  The image below indicates the wind field of Earl at 2:30 AM EDT, Saturday, September 4, 2010. The contours are displayed in knots. Notice the area of 60 kt winds to the SE of Earl (yellow areas) but the highest sustained winds on the west side are only in the 40 kt range.

The graphic below shows the winds at 5:30 AM EDT, Sept. 4, 2010, when Earl was SW of Nova Scotia. Notice the much higher winds on the right side of the storm.

The graphic below was valid for 9:30 EDT, Sept. 4 right before Earl made landfall near Western Head, Nova Scotia at 10:00 AM EDT. Notice the continued asymmetry with the strongest winds to the east of the center. Thus, much stronger winds occurred in the more densely populated area of Nova Scotia near Halifax. Also, notice the very light winds with an eye-like feature at landfall.  I spoke with some friends that have a weather station in Mahone Bay and they experienced the very light winds and the sun coming out during the passage of the “eye” of Earl.

Earl made landfall at Western Head, Nova Scotia as seen on the map below. The eye passed directly over Lunenburg, Mahone  Bay and Chester. An observer in Mahone Bay noticed that the sun came out as the eye passed over that location.

 Here is a picture I took last year from the plane flying into Halifax showing the harbor area.

The next picture is of the Mahone Bay area showing the gently sloping lanscape and protected harbor. fortunately, Earl hit at low tide, so there was no problem with storm surge flooding.

I took the next picture on beautiful Kaulbach Island where the private weather station there recorded wind gusts of 68 MPH. The only damage was downed trees. Electricity was out for a while but has been restored in Mahone Bay.

Large trees were uprooted on Kaulbach Island in the Mahone Bay area. (Picture courtesy Jefferson Harkins)

Large swells of up to 25 feet continued to be generated by Earl into Saturday evening as seen in the image below.

 Gaston had been downgraded to a remant low earlier this week. However, today there are signs of better circulation and some convection near the center of circulation. Gaston has been battling drier air and was the primary reason for its temporary demise. Long range models redevelop the storm, though, and some show Gaston eventually threatening parts of the Southeast and possibly Florida. Invest 99L does not look as strong as another tropical wave to its SW. There is another wave moving off Africa to the east of Invest 99L. Long range models develop this wave into a hurricane, which would be named Hermine unless another system develops first. A Gulf low has developed in the Bay of Campeche, as well.

Water vapor imagery below shows all the dry air with the Saharan Air Layer that sapped Gaston’s strength. The atmostphere is more moist closer to the Caribbean.

In addition, to the storm that could become Hermine, the METEOSAT image below shows two additional strong convective clusters that will likely exit Africa in the next week and could develop into tropical cyclones. 

The GFS model valid Friday at 8AM shows a rejuvinated Gaston near Hispaniola and another tropical cyclone in the eastern Atlantic.