Screen Shot2015-10-01 06_16_15If you have not heard yet, there has been a shift with the projection of Major Hurricane Joaquin.  The National Hurricane Center track map is often the best to use since it includes not only their thinning, but the cone or margin of error. I made sure to point that out when the center line was up the Chesapeake Bay on yesterdays outlooks.  That was when it looked similar to Isabel in 2003.

This morning the track moved east, but still kept Maryland and the Mid Atlantic in range. It is likely the next map will be a little farther east. NHC still has Joaquin adjacent to Atlantic City Tuesday morning, down to a tropical storm due to the colder water. Note that most of the action would be ahead of the storm Sunday to Monday, to tracking this before expected landfall impacts the weekend leading up.  The cone of uncertainty or margin of error still includes Maryland and a push completely and safely off the coast. There are no guarantees. Even when a storm is about to make landfall, typically for 300 miles of coastline in a warning, only 100 miles get the main impact. Those are just the odds we deal with in weather prediction and public preparation.

Why such a change?

The GFS Model I have been showing got a major upgrade from the National Weather Service last year to compete with the more accurate European Model.  But look at the change just from model runs 8 PM Wed to 2 Am Thu model plot for Sunday night.  While there was already a move on to the east, the 6 hour span made for a huge jump of roughly 200 miles different in the plot.

GFSChangeJoaquin

 

How could that be so different?

  1. The hurricane is stronger than expected. Reaching Category 3 status last night was ached of schedule. A stronger storm will not get pushed or pulled around from other weather systems as easily. It can be the bully instead.
  2. The drift to the west southwest towards the Bahamas is slow. I have been stressing that today is the day it makes the turn to the north. But a delay of a few hours doing so, would completely change the time Joaquin would interact with the same weather system in the US that is bringing us chilly rain for a few days. If they meet up later, that would allow our system to move farther and steer the hurricane farther to the east.
  3. More weather balloon launches. Weather modeling is fed by a network of weather balloons launched every 12 hours. This carries a package of instruments to gather data in a column up from the ground to above the clouds. The launches occur at 8 AM and 8 PM EDT. That data input plus a few hours of heavy computer calculations give us forecast maps a few hours later based on that data.  Many models now update in between launches every 6 hours with new data from ground observations, satellite data, and even reports from commercial aircraft on their flight paths.
    • More balloons added in major events. The National Weather Service enacted a policy to increase the balloon launching to every 6 hours for more data ahead of the hurricane.  That was used in the morning’s 2 AM models.  Either that data increased the accuracy, or the models did not know how to handle the increased data at a time it was not accustomed to.

What to think now?

I told one of my clients this scenario this morning. My philosophy has always been to wait for the next main hour modeling to see if there is a trend with a major shift in storm track.  Predicting the weather is very complicated. I wish it was as easy as say what to wear or if you even with happen. But a potential major event like Joaquin has so many subtle factors that can result in an abrupt course change.

Cliché

I know this will feed into the jokes, but yes there is a chance this is a boom or a bust. A track east would mean rain this weekend from a different event and then nothing from the hurricane in the Mid Atlantic. I would lean on this for now:

  • Plan for moderate to glancing blow: Sunday through Monday
  • Direct hit odds less than 25% chance

I will have another update after the next round o computer models arrive and close to the time of the 11 AM NHC update.

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