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8/15/05 FCST: Tropical Storm Irene (extratropical)

TD 9 has formed in the eastern atlantic and should continue generally to the W or WNW over the next few days. All models bring the system north of the islands but now that we have a closed low they should have a much better handle on the track. As the NHC mentions in their 5pm discussion, the depression is forecast to remain in a low-shear environment at least thru the next 48h so strengthening to tropical storm status and eventually hurricane status seems inevitable.

EDIT- There have been too many friggin status changes on this system!
 
Re: 08/04/2005 TALK: Tropical Depression Nine

the depression is forecast to remain in a low-shear environment at least thru the next 48h so strengthening to tropical storm status and eventually hurricane status seems inevitable.

If there is one thing about tropical forecasting, it's that it is very unreliable. This isn't a comment on the actual forecasts (or the forecasters), but on the "nature of the beast". There is so little data collected over the Atlantic that models are hardy reliable. Through in the fact that tropical system genesis is hardly well understood, and you have the making of a very unreliable beast. Looking at the shearing that is currently taking place of the system, I'd wouldn't be surprised to see it never reach T.S. status.
 
NHC Quote "...TROPICAL DEPRESSION FIGHTING A HOSTILE ENVIRONMENT..."

I agree with Jeff's statement. Based on what I've seen over the last 24 hours...I don't see very much potential for intensification. If anything it looks like it may crap out or remain at depression status throughout it's lifespan. Jeff stated it very well...these things are very unreliable and can also be unpredictable so things could change in the next couple of days...but right now I don't see that happening.
 
Doh! Well, I guess this goes to show just how little I know about tropical system intensity forecasts as well! LOL T.S. Irene was just named.
 
NORMALLY BY THIS DATE ONLY TWO NAMED STORMS
HAVE FORMED.

TD 9 has been upgraded to TS Irene as of the 15z advisory. Relatively cool SSTs and moderate shear should hinder strengthening for at least a couple days. I really don't see this strengthening beyond 45kts or so and, given the current environment, I'm actually surprised it attained TS status.
 
If there is one thing about tropical forecasting, it's that it is very unreliable. This isn't a comment on the actual forecasts (or the forecasters), but on the "nature of the beast". There is so little data collected over the Atlantic that models are hardy reliable. Through in the fact that tropical system genesis is hardly well understood, and you have the making of a very unreliable beast. Looking at the shearing that is currently taking place of the system, I'd wouldn't be surprised to see it never reach T.S. status.

I would agree for the most part, especially for the intensity part of forecasting, which we have very little skill in. You are right, the further out you get in the Atlantic the less reliable the track forecasting is, particularly in cases where you have changing steering flow patterns. Overall, however, track forecasting for Atlantic TC's is pretty darn good nowadays as compared to even 10 years ago.

I'm not sure what to think about Irene right now. These sheared TC's tend to be rather tenacious, taking a long time to completely dissipate, and this one obviously still has a vigorous LLC. As long as it can hang on to that and keep periodic bursts of convection going over its center, as it is right now, it could stand a chance. It's likely to turn north into the weakness in the ridge caused in part by Harvey.

I recall that the models did a pretty good job in forecasting cyclogenesis with Irene. The UKMET and GFS both were consistently developing it when it was still a wave just coming off the African coast, while the NOGAPS never showed much. As a general rule of thumb, when at least 2 models are forecasting development of a wave in the 2-3 day range, it vastly increases the likelihood that they are right.

Dan
 
Irene is sure not looking healthy in the near term with persistent shear but with a little time she might just get going...
The past few runs of the ECMWF show Irene to develop into a tiny hurricane as it moves westward into warmer SST's, then stall the low hanging out in the Bermuda Triangle.
Looks like a Eastern US landfall just north of Florida is possible at this time.
Question still remains - hurricane, tropical storm/depression or rain shower?
 
Irene is sure not looking healthy in the near term with persistent shear but with a little time she might just get going...
The past few runs of the ECMWF show Irene to develop into a tiny hurricane as it moves westward into warmer SST's, then stall the low hanging out in the Bermuda Triangle.
Looks like a Eastern US landfall just north of Florida is possible at this time.
Question still remains - hurricane, tropical storm/depression or rain shower?

Yep. the ECMWF has started to be consistant on bringing it westward.. The GFS did in the 6z and the 12z seems to loose it but showed a trend westward.. As long as Irene stays weaker, it should continue to come westward.. As a weak sheared storm it will be driven along by the trade winds instead of the mid and upper level steering currents.. Could be interesting come next week..

Jesse V. Bass III
http://www.vastormphoto.com
 
Im not to optimistic about this storm. In addition to the decent chance of it just dissipating or staying weak, I think its allready got way too much latitude... and will probably recurve away from the US.
 
I'm still very optimistic of any chance of this thing nearing US soil by about 1200 miles. Don't think it will undercut the trough....looks like a fish to me.
 
The Chesapeake-Potomac Hurricane in 1933 came in at a high latitude. Hurricane Felix in 95 was also a storm that traveled westward at a high latitude. It might be a trait more common in very active seasons?
 
Interesting point on high latitude storms Michael. Both the Chesapeake-Potomac Hurricane in 1933 and Hurricane Felix in 95 were within six days of each other in August. Felix was the 17th and Chesapeake-Potomac was on the 23rd. Interesting timing...
It appears now that Irene will climb in latitude a little over the next 24 hours according to a statement I just read. Storm movement is WNW @ 17kts.
 
Irene is still a tropical depression as of the 5pm advisory, but it seems to be trying to organize some. It is still moving west and NHC's current track takes it northwest and then turns it more to the WNW by Friday, towards the U.S. Hurricane Andrew did a similar thing (moved towards the north/northwest and then turned west) but Irene will probably be further to the north. I am not very good at forecasting but I think a landfall in Georgia or South Carolina is possible. :?:
 
hmm the latest global models... gfdl...nogaps...ukmet... have the trough bypassing the storm and leaving irene hanging out somewhere in the vicinity of bermuda with little forward speed in the 5 day range. I wonder why the NHC track is well south of this.

the high off florida... if that can grab hold of irene and loop her west...
 
Looks like NHC track is S of 3 of the models in their suite, but N of 2 others, and N of the extrapolation of current movement. Per latest forecast discussion, seems NHC is hanging their hat on maint. of Bermuda high; while the models diverge some on this solution, probably a good climatological call. Irene has been called an adolescent in some quarters, notably Hurricane Hollow Network, but a drifting tropical low entering decent environment for intensification over next 2 days bears watching. One of those Outer Banks close calls might yet be in the offing.
 
If Irene explodes in the next 4 days it will move more to the west and the Carolinas will take a hit by a potentially strong hurricane!
 
Things are starting to look interesting... Im in boston right now so a cape hateras landfall might be chaseable. Its a 12 hour drive or so.
 
Wow. I would encourage anyone at all interested to read the latest NHC discussion on Irene. Very insightful, and very interesting. To take a quote:

"THE GFS 10-MEMBER ENSEMBLE MODEL HAS
MADE A 450 NMI WESTWARD SHIFT AT 120 HOURS."

With the passing hours, concerns of too northerly latitude and entrainment w/ upper trough passages seems to diminish. True - the storm hasn't exactly gotten it's act together (can't even pinpoint the true position of the surface low!), but plenty of time left for spin-up given favorable environment....which position and forecast track indicate will be a very distinct possibility over the next few days. Any indication of approach near Carolinas, and I will be to the OBX or Charleston within hours.
 
Latest NHC forecast shows we may have another diaster by Monday or Tuesday of next week.
 
Very happy with the prospects of a possible impact here in CT by Thurs or Fri of next week. Models suggest that the ridge centered near Bermuda will shift to the east allowing for Irene to make a northerly turn. If this holds true, New England will likely see its first tropical cyclone since Floyd in 1999.
 
Irene has become much better organized overnight and presents a pretty good Visible satellite presentation, even though convection is slighty elongated from NW to SE. Top winds are up to 50 mph, and minimum central pressure is at 1000 millibars. Current motion is west-northwest at 17 mph. At this point the NHC is forecasting Irene to become a hurricane by early morning on Saturday and then they have left the intensity forecast at 75 knots through 120 hours. The reason they give for not showing further intensification is that Irene will be passing through some dry air as it moves towards the Carolinas. From the NHC 11 A.M. discussion:
SSTS ARE EXPECTED TO REMAIN BETWEEN 28.5C AND 29C...AND VERTICAL
SHEAR IS FORECAST BY THE SHIPS MODEL AND THE VARIOUS GLOBAL MODELS
TO REMAIN 10 KT OR LESS THROUGH 120 HOURS. SO THE ONLY INHIBITING
FACTOR AGAINST SIGNIFICANT INTENSIFICATION IS THE VERY DRY
MID-LEVEL AIR THAT IRENE WILL BE NAVIGATING THROUGH. THE OFFICIAL
INTENSITY FORECAST IS SIMILAR TO THE SHIPS MODEL THROUGH 72 HOURS
...AND THEN IS SLIGHTLY HIGHER AFTER THAT WHEN THE SHEAR IS
FORECAST TO DROP TO ABOUT 5 KT WHILE THE CYCLONE WILL BE MOVING
SLOWLY NORTHWARD NEAR THE WARMER GULFSTREAM.

So aside from the very dry mid-level air, everything looks conducive to possibly significant strengthing of Irene. And looking at the forecast models, this air won't be nearly as dry as the air she was contending with for most of her lifecycle. She's a scrappy little storm, and I'm willing to bet that with the low shear and 28.5-29 degree SST's in the Gulfstream, she will overcome this dry air with no problem. Don't forget that Andrew was a tropical depression/storm for a good portion of his life east of the Bahamas, too. You all know what happened next.
The current NHC track takes her to about 200 miles southeast of Wilmington and then curves her north and has her just barely missing Cape Hatteras before she continues toward the Delmarva Peninsula. At this point I'm guessing landfall will be sometime on Tuesday or early Wednesday between Wilmington, North Carolina and Dover, Delaware. Unfortunately, this looks like another potential Isabel to me. And everyone remembers how much havoc Isabel wreaked. Except if Irene overcomes the dry air at mid levels, all the other factors are there for the potential for Irene to be a Cat 3 major hurricane at landfall.
Oh, and by the way, shouldn't we rename this thread Tropical Storm Irene, since she's regained her strength? :D
 
Irene is just starting to look like an organized tropical system this morning! Convection has been persistent overnight and seems to be exploding at the moment. It appears Irene moved far enough away from the upper level low to its SW that was shearing it apart the past day or so.

I am very skeptical that Irene will have enough time in the shear-free environment to become a major hurricane, as there appears to be an upper low 500 mi east of Miami or so (probably there partly due to the compact high off the GA/FL coast). The track will probably recurve before landfall in the US, though it is definitely not out of the realm of possibilities that it could hit the U.S. A shortwave moving through the northeastern US may weaken the ridge enough for Irene to make Irene drift north a bit. The curve away will most likely happen when the trough progged moving through the northern plains today makes its way east.

The GFDL intensity and track forecast is basically the NHC consensus, recurving Irene just off the coast of Cape Hatteras, NC. The UKMet continues to be further east than the consensus, but has been moving its forecast west with time.

Hopefully Irene will not make landfall, but if it does, it probably won't be much more than a low-end category 2 hurricane. (But that's just my opinion)
 
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