Arthur now a Hurricane

RGB Satellite imagery near advisory time at 11am EST.
RGB Satellite imagery near advisory time at 11am EST.  Eye now re-emerging from central dense overcast.

Hurricane Hunter Aircraft, doing nearly constant investigation into Arthur, found that the storm had strengthened to reach Hurricane strength. As of the 5am EST advisory, Hurricane Hunters found a region of winds 70-75mph near the surface, stronger winds at flight level, and a minimum central pressure of 985mb. Further, satellite derived intensity estimates supported the idea that Arthur had become a Hurricane. Arthur strengthened further this morning and is a category one hurricane with max sustained winds of 90mph as of the 11am EST intermediate advisory from the National Hurricane Center. Arthur has a minimum central pressure of 981mb and is currently headed north-northeast at 14mph.

Tropical Storm conditions are set to begin in South Carolina and spread up the coast to North Carolina this afternoon, then spread further to the Atlantic coast of Virginia tonight and tomorrow morning. Hurricane conditions are possible along the immediate coast in the Hurricane warned areas, and in isolated areas inland and to the right of Arthur’s track. The National Hurricane Center has storm surge inundations of 3-5ft forecast for the Hurricane warned areas, should peak storm surge occur at high tide. These peak surges occur in areas of onshore wind. Hazardous sea conditions are spreading northward to North Carolina this afternoon.

Tropical Storm Warnings extend along the Atlantic Coast from South Santee River, SC to Surf City, NC. They become Hurricane Warnings from Surf City, NC to the North Carolina/Virginia border (including Pamlico sound and eastern Albemarle sound). Tropical Storm warnings resume at the North Carolina/Virginia border and extend along the Atlantic coast to Cape Charles light (including western Albemarle sound and the mouth of Chesapeake Bay). A Hurricane Watch is also in effect from the South Carolina/North Carolina border to Surf City, NC and may be upgraded to a warning should the center wobble to the left, or should the hurricane force wind field expand on the west side of the center.

11am EST surface wind field with valid watches and warnings.
11am EST surface wind field with valid watches and warnings.

Again, very little has changed in terms of track reasoning this morning. An upper level tough now in central Great Lakes region is pushing eastwards and Arthur is getting caught in the deep layered southwesterly flow ahead of this upper level trough. Now moving north-northeasterly, Arthur should begin to turn more northeasterly this afternoon. As I mentioned yesterday, very small changes in the angle of trajectory can mean the core of the Hurricane crossing inland or remaining offshore. Today the track has shifted very slightly to the left and now it appears likely that the core of Hurricane Arthur is going to cross the coast in eastern North Carolina, somewhere in the Hurricane warning area. Near the center and out to 25 miles away from the center (mainly to the east) there will be an isolated area of hurricane conditions after midnight tonight. It is important to remember that a Hurricane is not a point – tropical storm conditions extend as far as 115miles from the center, while squally showers with possible tornadoes extend even further.

Hurricane Arthur's eye can be seen on long range radar out of Wilmington, NC at 11:03am EST. Spiral bands with gusty/squally embedded showers are moving ashore in South and North Carolina already.
Hurricane Arthur’s eye can be seen on long range radar out of Wilmington, NC at 11:03am EST. Rain bands with embedded gusty/squally showers are moving ashore already.

Some additional strengthening is possible today as Arthur makes a final approach on North Carolina, and Arthur is now forecast to become a “moderate” category two hurricane before landfall tonight. Yesterday, dry mid-level air near the center was keeping core convection shallow on the western side of Arthur (likely slowing intensification to a Hurricane yesterday). However, today it appears that very little remains of this dry air, and even the deeper dry air to the north has modified somewhat and even moved further from the storm – that area has filled in a bit with showers as seen on radar and satellite imagery. Wind shear remains low as Arthur has maintained control of the upper level anticyclone which ventilates the storm aloft. Further, Arthur is still over the Gulf Stream’s deep warm waters. The environment is more favorable to sustain or strengthen a hurricane today than it was yesterday.

As Arthur becomes further drawn into the southwesterly flow ahead of the upper trough, mid-latitude jet streak dynamics may help ventilate Arthur further before the storm begins transitioning to an extra-tropical storm. Favorable environmental conditions, possibly becoming more favorable, leaves the possibility for rapid intensification on the table. It appears that Arthur will be holding its own, or strengthening when it makes landfall in North Carolina tonight.

Friday, the storm accelerates northeastward and moves away from the Outer Banks. Arthur then passes offshore of Cape Cod, MA on Saturday (possibly brushing the coast there with showers and tropical storm force gusts). Saturday night into Sunday, Arthur moves into Atlantic Canada and becomes a violent post- or extra-tropical cyclone there, with hurricane force winds. Eastern Maine, New Brunswick, Nova Scotia, Prince Edward’s Island, and Newfoundland may see gales or even isolated hurricane conditions from the remnants of Arthur this weekend. As Arthur becomes post- or extra-tropical, it should draw a cold front across the western Atlantic on Saturday. Returning moisture and convergence ahead of that front could bring showers to Bermuda early on Saturday, while the front itself could bring showers and possible thunder Saturday night clearing out into Sunday.

Refer to the National Hurricane Center for the latest official advisory information on Hurricane Arthur. For local official weather information see the National Weather Service. For official information related to Bermuda, see the Bermuda Weather Service.


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