Aug 252011
 

Thursday, 25 August 2011: 11:00 p.m. CDT

 

Hurricane Irene track forecast valid 11:00 p.m. EDT.

Hurricane Irene track forecast valid 11:00 p.m. EDT.


 

Well, it’s finally come down to this: Hurricane Irene stands a high probability of having significant impacts on not only the Outer Banks of North Carolina, but much of the Mid Atlantic and Northeast coastline. Irene is a large storm, with maximum sustained winds of 115 mph. Hurricane force winds extend seventy miles to the northeast of the eye, and 50 miles to the northwest. That means even though the eye may only be skirting parallel to the Mid Atlantic coast this weekend, hurricane force winds will be felt well inland all along the Mid Atlantic and Northeast.

Irene’s minimum central pressure has dropped to 942mb, but that still hasn’t translated to an increase in maximum sustained winds. The lack of immediate wind increase may be the result of an eyewall replacement cycle. But Irene is expected to strengthen over the next 12 to 24 hours.

Hurricane Irene is growing in size and is not only likely to cause widespread power outages and damage across the East coast, but is also going to bring a damaging storm surge. Her winds are forecast to increase to 125 mph as she approaches the Outer Banks of Norther Carolina (If you live there you need to be evacuating right now!). Then wind shear is expected to increase this weekend, causing a slow but gradual weakening. But don’t let that make you drop your guard — Irene is a large storm. Hurricane force winds will likely extend at least fifty miles or more to the west and north of the eye this weekend. That is enough to cause widespread power outages. I think it’s safe to say Irene is going to have lasting impacts all across the Mid Atlantic and Northeast.

This entire situation is reminiscent of Hurricane Ike (for me I mean, not in storm comparison, although Ike was also very large) because Ike hit Galveston/Houston not long after I had moved from Houston to Connecticut! Now, having recently moved back to Houston, I find myself staring at yet another very large, intimidating hurricane heading to my previous home. Maybe the big storms wait until I leave to hit, who knows. It’s for the best though. After 60+ inches of snow this winter, my apartment in Connecticut had more water leak problems through the walls and roof than I’d like to get into. Follow that with a hurricane bringing flooding rains (see image below) and I think that it’s better I’m not there. But the weather enthusiast part of me is still a little jealous!

’till next time,

- Jim

 

Visible satellite image of Hurricane Irene valid August 24 as she approached the Bahamas.

Visible satellite image of Hurricane Irene valid August 24 as she approached the Bahamas.


 

 

Infrared satellite image of Hurricane Irene valid the evening of August 25, 2011.

Infrared satellite image of Hurricane Irene valid the evening of August 25, 2011.


 
Forecast precipitation in inches for the duration of Hurricane Irene.

Forecast precipitation in inches for the duration of Hurricane Irene.


 

Aug 242011
 

Wednesday, 24 August 2011: Early a.m.

 
Hurricane Irene forms a well defined eye as she approaches the Bahamas…

Infrared satellite image of Hurricane Irene valid 0415 UTC August 24, 2011.

Infrared satellite image of Hurricane Irene valid 0415 UTC August 24, 2011.


 

Hurricane Irene continues on a west-northwest heading towards the Bahamas, and is expected to turn more towards the northwest within the next twenty four hours. In the image above you can clearly see a well defined eye, and as a result Irene’s central pressure has dropped to 969 mb. However, this has not yet resulted in an increase in maximum sustained winds. Winds have actually decreased to 90 mph due to dry air to the west and some lingering 10-15 knot wind shear. But I think it’s safe to say that given the well defined eye feature and upper level outflow pattern that Irene will soon strengthen. At least that’s what the official forecast says, calling for Irene to reach maximum sustained winds of 125 mph in 48 hours! (That would make Irene a strong Category 3 Hurricane).

 

Large infrared view of Hurricane Irene valid August 24 early a.m. CDT.

Large infrared view of Hurricane Irene valid August 24 early a.m. CDT.


 

The track forecast has shifted away from much of the Southeaster U.S coastline. As seen from the official NHC track forecast (below), Irene is expected to make landfall over the outer banks of North Carolina followed by a trip up the Northeast coast. But residents all across North Carolina should certainly still pay close attention to Hurricane Irene given the inherent track forecast errors beyond three days.

 

Track forecast for Hurricanen Irene valid 11p.m. EDT August 23, 2011.

Track forecast for Hurricanen Irene valid 11p.m. EDT August 23, 2011.


 

This trend to the east in the forecast is due to computer models shifting further east (see below). As stated in the previous post, Irene’s track will depend significantly on the strength of a trough (or troughs) moving through the Northeastern U.S. later this week. Computer models now have a better handle of these troughs and indicate they will be a bit stronger than previously suggested. As a result, most guidance — including the tropical model suite– suggests Irene will pass over the outer banks of North Carolina or miss them to the east. I think both scenarios are possible, but honestly would place a higher probability on the outer banks being hit.

 

Tropical model tracks for Hurricane Irene valid 00z August 24, 2011.

Tropical model tracks for Hurricane Irene valid 00z August 24, 2011.


 

One of the more significant model trends over the past 24 hours is seen in the GFDL tropical model. On the previous post I showed how the GFDL was forecasting Hurricane Irene to make landfall over south Florida near Miami. Well, the 18z August 23 run of the GFDL (see below) has Hurricane Irene making landfall over eastern North Carolina, not far from the outer banks! The HWRF tropical model shifted east too. It now has Irene missing the outer banks to the east. So, it’s going to be interesting to see how close of a call this actually turns out to be with this storm. Based on the data at hand it seems to me that the outer banks stands a higher probability of being hit vs. a miss to the east. But it’s still too early to be completely locked into a landfall forecast….

 

18z August 23 GFDL model for Hurricane Irene, showing landfall over eastern North Carolina on the evening of Sunday, August 28, 2011.

18z August 23 GFDL model for Hurricane Irene, showing landfall over eastern North Carolina on the evening of Sunday, August 28, 2011.


 

In any case Hurricane Irene should be moving into a weaker wind shear environment soon. As daylight hours move in upon this storm, I imagine some amazing visible satellite images will become available, eliminating an amazing eye structure and outflow pattern.

That’s all for now. Thanks for reading.

- Jim

Aug 222011
 

Monday, August 22, 2011

 

Track forecast for Hurricane Irene valid 8p.m. CDT August 22, 2011.

Track forecast for Hurricane Irene valid 8p.m. CDT August 22, 2011.


 

Hurricane Irene has moved north of the mountainous island of Hispaniola, which has been the key in her strengthening into a hurricane. Maximum sustained winds are 100 mph, making Irene a Category Two Hurricane. Irene is expected to continue moving generally west-northwest for the next couple days and strengthen as she remains over warm waters and wind shear slowly weakens over the next few days.

By mid-week an upper level trough moving through the Northeastern U.S. will cause a weakness in the ridge centered over the Atlantic (which is currently steering Irene), and cause Irene to turn more towards the northwest and over the central Bahamas. Then later in the week another trough is expected to move through the Northeastern U.S., but computer models do not agree on the strength of this trough. Thus, they disagree on how much of an impact it will have on the track of Irene late this week into the weekend.

 

Tropical model tracks for Hurricane Irene valid 00z August 23, 2011.

Tropical model tracks for Hurricane Irene valid 00z August 23, 2011.


 

For now, the National Hurricane Center has Irene making landfall on Saturday near the South Carolina/North Carolina border. But uncertainty is pretty high on what the actual impacts will be along the entire Southeastern U.S. coastline. There are many tropical models suggesting Irene may begin to curve towards the north-northeast as she approaches the Carolinas, implying she may only clip the outer banks of North Carolina. Then again the European model — which tends to be quite a reliable model — has Irene making landfall along the border of the Carolinas. Additionally, the GFDL tropical model insists upon Irene making landfall just north of Miami, FL!

 

August 22 18z GFDL model for Hurricane Irene valid Friday morning, August 26.

August 22 18z GFDL model for Hurricane Irene valid Friday morning, August 26.


 

It’s far too soon to make any definitive landfall predictions at this time. But it seems pretty likely Irene will be the first major hurricane of the season to threaten the Southeast coast. All residents along the east coast of Florida, South Carolina and North Carolina should closely monitor Hurricane Irene. For updated forecast tracks on Hurricane Irene, please visit the National Hurricane Center’s Website. As far as chasing Irene, Stormagsm team members are getting ready for possibly the first hurricane chase of the season!

- Jim