SATURDAY SEPT 2 IRMA UPDATE… US LANDFALL THREAT SEEMS TO BE INCREASING
201709.2 first officer DT Rex reporting...
There is no doubt that all the models early Saturday morning shifted the track of hurricane IRMA to the west as it moves through the Bahamas. This brings IRMA closer to direct contact / landfall on the southeast or Middle Atlantic coasts ...depending on the model... and NORTH of the Fl/ GA border . This shift to the west can be seen on the early Saturday morning opertional or " regular" GFS model run as well as the 6z GFS model .. the 0z GFS ensembles... the 6z GFS ensembles ... the 0z operational European and the European ensembles.
This is a disturbing trend which has to be watched carefully. It seems it is time to pull out the old PowerPoint presentation of hurricane patterns for the East Coast and re-post it so anybody can understand the significance of these various atmosphere of features that going to forecasting a East Coast hurricane track.
When you are dealing with East Coast hurricanes there are essentially 4 different types of tracks to deal with (I briefly went over these in a previous report).
- The first and the most dangerous type of hurricane track for the East Coast is when the hurricane is forced INLAND on a northwest trajectory. We saw this was hurricane Isabel in 2003 ... and we also saw this in 1954 with hurricane Hazel and with hurricanes Connie and Diane in 1955.
- The second type of East Coast hurricane track is the more typical one ... the Coastal. In this track here Hurricanes tracks along the coastal areas passing very close to Cape Hatteras NC and Cape Cod and southeastern Massachusetts or eastern long island. We saw this sort of track with hurricane Gloria 1985... hurricane BOB in 1991 and hurricane Floyd in 1999. The sort of Hurricane tracks are not nearly as devastating because most major metropolitan areas are on the western side of the hurricane which is the substantially weaker side. Not only is the movement vector against the wind vector but the western side he hurricane often gets disrupted by pulling in large amounts are dry air from the interior portions of the eastern US.
- The third type is with the hurricane passes between the East Coast and Bermuda which in the old days was referred to as a "slot hurricane".
- The 4th kind of East Coast Hurricane is also extremely rare. It is called a FM hurricane ( FM= Fst Mover) . Fast moving hurricane is where the core of system races up the East Coast at speeds greater than 50 mph. We saw this with the great New England hurricanes 1938 and hurricane Donna in 1960. Both of these storms bought hurricane conditions to much of the East Coast even on the western side of the hurricane. The faster Foward speed keeps the core quite strong and prevents the dry air from being pulled into the system and causing weakening and disruption
Ths morning IRMA is pretty much unchanged as is still strong category 2 hurricane ,. All the data clearly shows IRMA is going to continue to steadily increase all the next 4-5 days. All the hurricane models continue to show that the system is going to pass north of Puerto Rico and head towards the Bahamas early next week. So that part of forecasts is also much unchanged
We can look of the upper air patterns to figure out why and how IRMA's track has shifted west on this Saturday morning. All of the models has shifted the track of IRMA westward slamming into various portions of the U.S. the East Coast sometime around September 10.
This first image shows the upper air maps from the GFS model from early Saturday morning. The GFS model has a massive ridge in the jet stream centered over the West Atlantic Ocean. This feature is commonly refer to as the "Bermuda HIGH" but the technical name of it is the western Atlantic ridge. There is also an equally strong ridge in the jet stream over the the Plains and into south central Canada. In between these two features we have a trough centered over the Midwest and specifically over the Ohio Valley that extended into TN.
It has always been a danger sign when we have a deep trough like this over the Great Lakes that stretches down into Tennessee and Georgia when a hurricane approaches the East Coast.
But on the morning of Saturday, September 9 ( a week from today) IRMA is approaching the coast and being squeezed between the ridge in the western land Atlantic and the trough which is extending down from Michigan into Kentucky and West Virginia. This forces the hurricane to take a due north or even slightly NNW track that results in a hit for eastern NC/ eastern VA central and eastern MD NJ NY NEW ENGLAND.
We can see what this looks like on the surface maps.. We see the approach of IRMA on the evening of September 8. The operational regular G FS model has a category 5 hurricane to the northeast the Bahamas at 900mb. This seems way overdone. By Saturday evening the GFS has category 5 hurricane rapidly approaching Cape Hatteras North Carolina 910 mb. Again this to be the strongest hurricane EVER threaten the East Coast since it was settled by a white Europeans in the 1600s. We are skeptical that IRMA is going to be that strong on September 8 or 9.
This next image shows the early GFS model from Saturday morning with a landfall on Saturday, September 10 very close to Wallops island Virginia or Ocean City Maryland as a monstrously powerful category 5 hurricane at 925 MB. This is of course absurd. From there the GFS model takes the hurricane right across the Delmarva and on top of Philadelphia or perhaps into Reading PA at 944mb on Sunday, September 10 in the afternoon hours. Obviously this would be extremely bad news for the Delmarva ... NJ... NYC... Long Island and Connecticut as the tremendous tidal surge woulds come pouring in from the Atlantic Ocean. The tidal surge would potentially be as bad as what they saw with Sandy.
As I stated earlier on this website and on the FB page the intensity of the hurricane on the GFS model is absurd. The sea service temperatures north of Cape Hatteras cannot support a hurricane this strong. That is why it has never happened before. Hence I made a comment about monkeys flying out of my ass. Of course that doesn't mean there are not going to be a few people out there who will misinterpret what I said or even outright lie about it. The issue is not whether IRMA is going to strike the U.S/ . the East Coast. The issue - is whether it will be a category 4-5 hurricane when it slams into eastern North Carolina Southeast Virginia ...the Delmarva ...or New Jersey or New England.
It won't be anything nearly that strong.
If we look of the GFS ensembles we see that the early morning run had three distinct clusters of possible landfalls. This is generally not a good sign that the model has a th good handle once the overall situation.
The early morning European model also shifted west and we can see that here. Again the European model shows a very strong ridge in the jet stream over New England and the western Atlantic Ocean forces the hurricane to take a wide turn when it approaches the Bahamas. According to the European model this massive ridge over the west Atlantic Ocean forces IRMA to make landfall south of Hatteras and very close to a the same intensity as hurricane Hugo in 1989 and on the South Carolina North Carolina Coast. approximately Myrtle Beach South Carolina. Unfortunately since the operational or regular European model stops at Day 10 we don't know where the hurricane goes from South Carolina.
If we look at the European ensemble we see that the vast majority of them bring IRMA very close to the coast then then parallels the coast sort of like what HELENE back in 1958. That was a category four hurricane which followed the coastal areas from Georgia to Cape Hatteras and then headed northeast out to sea. Of course the are several members of the European ensemble which to show a landfall in Florida or Georgia South Carolina.... But still the majority of the European ensembles show a close near miss or glancing blow.
Finally here is the updated 6z GFS model and it is pretty close carbon copy to what the previous run of the GFS was showing. The 6z GFS model has a category 5 hurricane either correctly over Cape Hatteras and just to the east on the evening of September 8 . from thee it has IRMA take IRMA due North a brushing the Delmarva Coast ...very close Ocean City and showing a landfall around Cape May NJ on the morning of September 10. Again the operational or regular GFS model continues to show an extremely intense record setting historic unprecedented powerful hurricane. And again I need to emphasize that this intensity is complete crap. From that position the 6z GFS model takes the hurricane due north over coast and New Jersey into New York City and up the Hudson Valley. This would be a devastating hit for New England as that entire region of the on the eastern side of the hurricane .
The 6z GFS ensemble is in close agreement this solution and has a concentrated cluster over Eastern North Carolina .
SUMMARY. As impressive as the shift to the west was this morning ...all the models it still needs to be pointed out the ensemble mean is often a much better and more realistic than trying to figure out whether the individual model had 192 hours is going to be correct. Most of the time the individual or operational models iare not going to be correct at Day 7... DAY 9... DAY 11. .
Again I need emphasize that the GFS model is simply way too extreme. At least the European model which has a 935mb category 4 hurricane hitting South Carolina is a least realistic and matches precedents.
Other reasons why I don't believe the GFS intensity to be valid has to do with the fact that IRMA is going to be a slow moving storm and it is going to pull a lot of dry air from the interior portions of the eastern US which will disrupt the system significantly. I also still think that IRMA coudl make a sharp right turn of off the Southeast US coast are still quite viable and I am not a convince that IRMA is going to make a direct impact on the eastern US