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Hurricane Irene Model and Forecast Discussion


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Tropical Systems tend to behave on their own. Remember Earl back in 1996 where we thought it will clip Eastern LI but instead missed the East Coast completely and only Eastern New England felt some effects from it. There was some Atlantic ridge I could remember. I won't be surprise this is the same case except it could brush the Carolines then make the turn to N to NE. I do see the possibility of it clipping Eastern LI then hitting Cape as tropical storm become extra-tropical where rain and some wind for Eastern LI and New England. Areas of the city and Coastal NJ will see lighter amounts of rain where closer to the storm could get into the heavier rains.

Hurricane Edouard from 1996? That was a totally different system with a totally different setup.

Sure, there is a chance this goes out, but there is a chance it is closer as well.

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I don't think it is realistic either, and as we have seen the EURO tends to over-intensify storms. I do think you can take away ideas about the track and rainfall rates. Pressure may be 20mb higher though.

That seems reasonable. Here are Euro predictions and the respective actuals for Earl last year for various locations just off the east coast (a bit further off the coast):

38N: Euro said 932 mb; actual was 961 mb; 29 mb too low

39N: Euro said 934-38; actual 961; 23-27 too low

40N: Euro said 941; actual 958; 17 too low

42N: Euro said 943; actual 965; 22 too low

The Tue 12Z Euro has 928 mb at 32N, 76W (at 96 hours) and 927 mb at 37N, 75W (at 120 hours). Even if 20 mb is added, we're still looking at 947 mb way up at 37N!

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SHIPS continues to be thoroughly unenthusiastic about intensification prospects for Irene.

Makes sense - it's a purely statistical-based guidance type and usually, hurricanes have maxed out after turning the corner. This one is somewhat unusual in that it attempts to buck that normalcy do to having some uniquely favorable deep layer mechanics combined with ample oceanic heat content. The SHIPs would not likely see a system moving N from this position given what more typically is in wait for those types.

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SHIPS continues to be thoroughly unenthusiastic about intensification prospects for Irene.

Ships model may want to look at some of the recent satellite pics...she is starting to look pretty healthy again. May be starting to get her act together again and that will likely start a more N tug to the motion as well. I'm really thinking Irene's favorite movie is "What About Bob"

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with the CMC and GFS on top of one another and the Euro making a discerned effort to come east, and seeing some of these early 18zs ...seems pretty clear a consensus along the lines of what Cheesenado was describing is coming into coherency.

Slower than normal moving Long Island Express - heh, we'll see how it goes.

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in regards to intensity forecast, SHIPS maybe picking up on the issue Irene is having with dry air...

the first pic is the 1900UTC screen grab from a pwat animation...the black dashed arrow indicating drier air circulating into Irene..

the 2nd pic is from the Infrared RGB loop from the NWS site: Irene still spewing arc clouds, and i have placed a yellow circle (in the center) where perhaps the untrained eyes on this board may have mistakenly thought Irene was trying to form an eye, in reality it was just the effects of dry air circulating to the center of Irene and choking off convection

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in regards to intensity forecast, SHIPS maybe picking up on the issue Irene is having with dry air...

the first pic is the 1900UTC screen grab from a pwat animation...the black dashed arrow indicating drier air circulating into Irene..

the 2nd pic is from the Infrared RGB loop from the NWS site: Irene still spewing arc clouds, and i have placed a yellow circle (in the center) where perhaps the untrained eyes on this board may have mistakenly thought Irene was trying to form an eye, in reality it was just the effects of dry air circulating to the center of Irene and choking off convection

Nice point there with the PWAT animation.

I feel uncomfortable dismissing the SHIPS. As long as we have moderate shear with this feed of dry air, ample intensification will be pretty difficult. The next 48 hours is the main period for potential strengthening based on SSTs, and Irene could end up squandering it because it's fighting off dry air the whole time. The other big negative in the SHIPS is relatively warm temperatures in the lower strat with the lower heights over the eastern US -- lower tropopause.

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A few RAOBs and we can get almost every model to agree on something.

Unfortunatly I think the New England impact is still far enough away to give models time to trend east.

ECMWF was way to far west with the last WPAC typhoon during the medium range.

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.

Unfortunatly I think the New England impact is still far enough away to give models time to trend east.

I think there's hope for weeniedom in that, while the 18Z GFS basically ends up in the same place as 12Z, it does so with a more pronounced westward wiggle off New Jersey than 12Z.

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I pointed this out last night but if you go back 72, 84 and even 96 hours the SHIP has done extremely well. When I reviewed it last night it was the only one at the forecast time of 84 hr that was forecasting ~90kt winds. Irene was ~ 85kt. And the rest of its forecasts has been the most accurate of all models and pretty close to reality. I'm going to ride the SHIP intensity forecast...even this period b/c it was one of the few at 6 and 12z maintained a steady intensity into the evening which is closer to reality than what most of the other models went for. Although have to throw NAM in on intensity, it forecasted the drop in intensity this afternoon. Track wise BAMD and CLP5 have a good track record so I'll bet on a blend of them. :thumbsup:

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Nice point there with the PWAT animation.

I feel uncomfortable dismissing the SHIPS. As long as we have moderate shear with this feed of dry air, ample intensification will be pretty difficult. The next 48 hours is the main period for potential strengthening based on SSTs, and Irene could end up squandering it because it's fighting off dry air the whole time. The other big negative in the SHIPS is relatively warm temperatures in the lower strat with the lower heights over the eastern US -- lower tropopause.

Irene has been battling dry air since the beginning...inhibiting RI...which people so desperately want...and if you look at the PWAT animation, Irene is heading into the Bahamas, into an area of drier air...i would not discount SHIPS, at all...the warm sst's are certainly helping Irene maintain...but i don't think they will negate the effects of dry air/shear...

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Irene has been battling dry air since the beginning...inhibiting RI...which people so desperately want...and if you look at the PWAT animation, Irene is heading into the Bahamas, into an area of drier air...i would not discount SHIPS, at all...the warm sst's are certainly helping Irene maintain...but i don't think they will negate the effects of dry air/shear...

Considering Irene's central pressure just dropped 7 mb in 5 hours, I'd caution you that the desire to prove how cool you are by anti-weenie-ing is a bias just as bad as being a weenie.

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Considering Irene's central pressure just dropped 7 mb in 5 hours, I'd caution you that the desire to prove how cool you are by anti-weenie-ing is a bias just as bad as being a weenie.

not trying to anti-weenie anything...and if this thing ever does undergo RI in the furture, then so be it...i was referring to the possible reasons SHIPS has been conservative with the intensity forecast...and so far it has done well...i make no claim about what will happen in the future with Emily...only posting about her past development up until the point in time i made that post...

and besides, we all have some weenie in us...some more than others...to deny it is ridiculous...

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not trying to anti-weenie anything...and if this thing ever does undergo RI in the furture, then so be it...i was referring to the possible reasons SHIPS has been conservative with the intensity forecast...and so far it has done well...i make no claim about what will happen in the future with Emily...only posting about her past development up until the point in time i made that post...

and besides, we all have some weenie in us...some more than others...to deny it is ridiculous...

Diane, you have been making excellent points this afternoon. The only problem is that despite bouts of dry air being ingested earlier today, I'm still not sure if it was more related to the ambient environment, or the downsloping off Hispaniola. If this thing intensifies significantly tonight, it was more likely the latter.

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Diane, you have been making excellent points this afternoon. The only problem is that despite bouts of dry air being ingested earlier today, I'm still not sure if it was more related to the ambient environment, or the downsloping off Hispaniola. If this thing intensifies significantly tonight, it was more likely the latter.

lol, you don't have to cherry coat it...if i'm wrong, i'm wrong...i did try to edit my post about dry air to include or "it's the inflow being disprupted by Hispaniola (max elevations on the island ~ 10,000ft) but the edit wouldn't work...i thought i posted that in a separate post instead...but maybe i forgot

i'm going to be wrong about a lot of stuff...but it's nice when someone tells you why instead of just teliing you you're an idiot...or tell me both...but at least tell me something i can learn from

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lol, you don't have to cherry coat it...if i'm wrong, i'm wrong...i did try to edit my post about dry air to include or "it's the inflow being disprupted by Hispaniola (max elevations on the island ~ 10,000ft) but the edit wouldn't work...i thought i posted that in a separate post instead...but maybe i forgot

i'm going to be wrong about a lot of stuff...but it's nice when someone tells you why instead of just teliing you you're an idiot...or tell me both...but at least tell me something i can learn from

You aren't necessarily being wrong about the presence of dry air either... its just despite all the dry air to the north and the south of our system, none of it seems to be getting ingested into the core. CUmet might be able to chime in later, but he made an excellent post back when Don was around that you need a shear vector in the opposite direction of the dry air in order to cause displaced inflow that can suck up the dry air. The 10-15 knots of westerly shear might be causing displaced inflow to the east of the storm, in the area where the total precipitable water is still quite high, so perhaps that's why we aren't seeing it contribute to harming the inner core.

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