Gonzalo now a Major Hurricane


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Hurricane Gonzalo’s center marked with a red x, and the track for the next 72hours marked by a red arrow. Bermuda is labelled.

Hurricane Gonzalo strengthened this morning as it exited the northeastern Caribbean and Leeward Islands and moved into the Atlantic. The pace of intensification slowed for much of the day as Gonzalo organized amidst some wind shear, but appears to have resumed and as of the 6pm Bermuda time advisory from the National Hurricane Center, Gonzalo was a major hurricane with 115mph 1-minute sustained winds and a minimum central pressure near 970mb.

Gonzalo continues to track northwestward around the southwestern periphery of a deep layer high pressure over the North Atlantic. This is taking Gonzalo over warm waters between 28 and 29C which is plenty warm to sustain a major hurricane. Gonzalo’s upper environment is also becoming more favorable for sustaining a major hurricane. Now that Gonzalo has a well defined core and conditions are becoming more favorable for development, some quick intensification is possible tonight and Gonzalo is expected to become a category 4 hurricane with 140mph 1-minute sustained winds in 36hours. Fluctuations in intensity are common in major hurricanes and are expected as Gonzalo’s core convective structure evolves and matures during this period.

Thursday morning sees Gonzalo tracking more northward as the high pressure retreats eastward somewhat and a trough moves off the US east coast. The southwesterly flow ahead of the trough begin to influence Gonzalo’s track, turning the hurricane toward Bermuda. Sea surface temperatures are lower, near 27C, as Gonzalo heads north toward Bermuda and wind shear increases in this southwesterly flow. These factors start Gonzalo on a weakening trend. This most recent forecast puts the center over Bermuda Friday afternoon as a category three hurricane with 115mph 1-minute sustained winds.

Any deviations either side of the current track for Gonzalo’s closest point of approach are impossible to pin-point with any skill at this time (~3-days in advance), but this allows us to discuss several scenarios that Bermuda should be aware of and preparing for:

  1. Gonzalo tracks directly overhead. Bermuda sees tropical storm force easterly winds increase to hurricane force friday afternoon, the eye passes over and winds drop to light and variable, then hurricane force winds resume from a more westerly direction before dropping off as Gonzalo moves away.
  2. Gonzalo tracks to the west of Bermuda. Tropical storm force easterly winds increase to hurricane force and veer southeasterly through southwesterly then decrease as Gonzalo passes by. Winds might continue to veer through to northwesterly as they decrease. No relative calm of the eye experienced.
  3. Gonzalo tracks to the east of Bermuda. Tropical storm force easterly winds increase to hurricane force and back northeasterly through northwesterly then decrease as Gonzalo passes by. No relative calm of the eye experienced.
    1. All of these scenarios include heavy rain that could lead to flooding of low lying areas particularly at high tide, squally showers that may spawn tornadoes/waterspouts, and very dangerous sea states that will likely result in coastal erosion and flooding.

With Bermuda in the cone of uncertainty for 72hours, it is looking increasingly likely that there will be at the very least tropical storm conditions (1-minute sustained winds between 39mph and 73mph) on Bermuda from Gonzalo, whether or not hurricane conditions (1-minute sustained winds greater than 74mph) occur still depends of the strength and size of the storm and its exact track. A Tropical Storm Watch will be issued tonight as Gonzalo gets closer and the confidence in the track increases. Ideally, preparations to protect life and property should be complete by Thursday night. Storm intensity can change quickly and in a short period of time, and small changes in track can make a huge difference when it comes to impacts, it is therefore imperative to follow the latest official information from the Bermuda Weather Service and the National Hurricane Center.

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