Issued: Thursday, September 2, 2010 620 am EDT/520 am CDT

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Hurricane Earl Discussion

For Information About Hurricane Earl with Maps, Images and Graphics, Go To: http://www.crownweather.com/?page_id=2972.

Reconnaissance aircraft investigating Earl have found 160 mph winds at 10,000 feet in the northeastern eyewall. A dropsonde in the eye of the hurricane found a 928 millibar central pressure. Based on this, Earl is a 145 mph Category 4 hurricane this morning. Earl is likely at or near peak intensity early this morning and I expect Earl to level off at Category 4 strength today.

Earl is tracking north-northwest at a forward speed of 18 mph. Earl is forecast to turn due north today and then north-northeast tonight through Saturday. The center of Earl is currently expected to remain about 50 to 75 miles offshore of Cape Hatteras at its closest approach to North Carolina, which is expected a little after midnight tonight. I still think a track right over the outer part of Cape Cod is very possible Friday night and then a track that takes Earl right over extreme downeast Maine during the predawn hours of Saturday morning.

Needless to say, any deviations to the west in the hurricane’s track is very scary given how strong it is forecast to be (borderline Category 3-4 as it tracks east of North Carolina tonight and a Category 2 hurricane as it tracks over the outer Cape Friday night).

I also wanted to mention that the new consensus model guidance forecasts that Earl will pass about 75 miles from Boston at its closest approach. If the model guidance continues trending westward, then hurricane force winds would become possible even for Boston Harbor.

The winds are forecast to increase on the outer banks of North Carolina later this afternoon with hurricane force winds with gusts to near 100 mph expected on the outer banks for a few hours either side of midnight tonight. Breaking waves as high as 15 to 20 feet are likely tonight along the coast of North Carolina and Virginia with a storm surge of 3 to 5 feet expected. This surge, combined with the high waves will cause significant beach erosion with sections of Highway 12 along the outer banks washed out in many areas. The high tide around 3 am Friday morning will be very dangerous.

Now, for the effects in New England: Hurricane force winds are becoming more and more likely across all of Cape Cod and the islands with hurricane force winds possible for extreme downeast Maine (southeast Washington County). Across the rest of New England, tropical storm force winds with gusts to 60 mph are likely along the south coast of southern New England and east and south of 495 in Massachusetts, including Boston. Areas east of I-95 in New Hampshire and Maine may also experience tropical storm force winds, this does include the cities of Portsmouth, Portland and Bangor. These winds are forecast to start Friday evening and continue through much of Friday night before diminishing quickly from southwest to northeast during Saturday morning. The heaviest tree damage with power outages are expected across Cape Cod and the islands and also in extreme downeast Maine.

A storm surge of 1 to 3 feet is possible along the entire New England coast with the highest storm surge values expected on the outer Cape, in Nantucket Harbor and the northeast facing coastline of Martha’s Vineyard during Friday evening’s high tide.

For those of you in eastern North Carolina (especially the outer banks) and southeast Virginia, please make your final preparations for the hurricane. For those of you in New England, especially Cape Cod and extreme downeast Maine, today is the day to prepare for hurricane conditions. If your home or business is vulnerable to high winds, cover all windows and doors with shutters or plywood. Move patio furniture and other loose objects indoors. Brace all exterior doors, including garage doors. If you need to make a trip to the hardware store, the grocery store or the gas station, do so today. Please consult your local media outlets for advice from emergency management officials on any evacuation orders.

I will try and write up an update on Earl sometime this evening.

Tropical Storm Gaston Discussion

For Information About Tropical Storm Gaston with Maps, Images and Graphics, Go To: http://www.crownweather.com/?page_id=3068.

I wanted to spend a little bit of time talking about Tropical Storm Gaston. Gaston has remained a steady state 40 mph tropical storm overnight, however, environmental conditions are favorable for intensification over the next 5 to 7 days. The only caveat to that is water vapor satellite loops shows that the storm is somewhat embedded in some dry air which could put a cap on strengthening. For now, I think Gaston will become a hurricane later this weekend.

Gaston is tracking just north of due west at a forward speed of 9 mph and the storm is forecast to slow down even more over the next couple of days as there are weak steering currents around. By late this weekend, high pressure should strengthen to the north of Gaston and cause a slight acceleration in the forward speed. Gaston poses an eventual risk to the Lesser Antilles in about 6 to 7 days from now.

The next tropical weather discussion will be issued by 7 am EDT/6 am CDT Friday morning. I am going to try and post an update on Hurricane Earl sometime this evening.

Disclaimer: All forecasts herein are made to the best ability of the forecaster. However, due to standard forecasting error, these forecasts cannot be guaranteed. Any action or inaction taken by users of this forecast is the sole responsibility of that user.