Hurricane Earl has intensified even further overnight, with maximum sustained winds of 145 mph (125 knots) and minimum central pressure of 932 mb.  The motion has also increased to 16 knots at a near due-northerly direction as of around 9 am EDT, which is very good news for the residents of the North Carolina Outer Banks and New England.  Hurricane warnings remain in effect for the North Carolina coast, where a storm surge of 3-5 feet is anticipated over the Outer Banks and Chesapeake Bay.  Hurricane watches have been issued for the coasts of Rhode Island and Massachusetts, as the center of Earl is expected to be right over Nantucket Island at around 2 am Saturday while barreling toward the Canadian Maritimes.  Yesterday, I looked at the water vapor imagery and noticed that Earl was enveloped in a massive reservoir of dry air aloft, with multiple dry-air intrusions into the circulation of the hurricane, and I thought this would hinder further intensification.  However, exactly the opposite transpired overnight as Hurricane Earl intensified into a category 4 storm!  The sea surface temperature anomaly map at left likely sheds some light as to how this hurricane overcame the dry air, as warm SST anomalies of 2-4 degrees C reside across the entire length of the already relatively warm Gulf stream just off the east coast of North America.  In fact, the raw SSTs show the warmest oceanic heat content just ahead of Earl off the Mid-Atlantic which will help Hurricane Earl maintain major hurricane status for the next 24 hours or so despite increasing upper-level wind shear.  Last night, the enhanced upper-level divergence between the subtropical anticyclone to the east and the advancing mid-latitude trough to the northwest likely aided in this intensification.  Stay tuned for updates throughout the day today, and also during landfall overnight, and be sure to check out TornadoVideos.net/live for any TVN chasers streaming live video...