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Hurricane Irene Model and Forecast Discussion


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The ECMWF is sniffing out the theta-e ridge in response to the height recovery downstream of the s/w (the one that won't reach British Columbia until Friday). While that should be noted, I think it also needs to be blended with the other models.

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Thanks for posting that! Wow... they are nearly identical... what strength does it look to be at near landfall in NJ and/or DE ish?

It looks to be 955 just off the NJ coast at f-102hr.

These are GFS wind speeds, so you need to interpret accordingly.

10mwind2011082412_09L_gfsenkf_cntrl_f114.gif

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18z SHIPS

13kt shear initially (down from 20+kt at 12z initially), dropping down to 7 kt by this evening and then staying less than 10kt. There is some evidence of this drop off looking at the IR, with more bands developing west of the system without any problems.

It is worth noting that the SHIPS keeps the intensity quite high as it heads northward, dropping it only 5kt (from 105kt to 100kt) during the 36 hour period from 48 hours at 30.3N to 84 hours at 36.9N, as well as keeping it at 92kt as it passes 40N.

Also, no surprise with the outer eye evident from observations by microwave satellite and recon

** PROBLTY OF AT LEAST 1 SCNDRY EYEWL FORMTN EVENT AL092011      IRENE 08/24/2011  18 UTC **
TIME(HR)   0-12  12-24(0-24)  24-36(0-36)  36-48(0-48)
CLIMO(%)    27     27( 47)      30( 63)      28( 73)     <-- PROB BASED ON INTENSITY ONLY
PROB(%)     65     72( 90)      78( 98)      33( 99)     <-- FULL MODEL PROB (RAN NORMALLY)

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It looks to be 955 just off the NJ coast at f-102hr.

These are GFS wind speeds, so you need to interpret accordingly.

.

Thanks! So in strength terms, the Euro and the GFSE seem to have the same general trends as Irene passes DE and NJ... except the Euro is of course noticeably stronger (and as mentioned previously, probably a bit too much as has been seen in the WPAC this year).... we could easily be looking at something in the 940s coming up that way though.

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The consensus of the early cycle 18z dynamic models shifted about 50-100 miles west from 12z:

This makes sense, and is really a reflection of the westward shift observed in the actual 12z model runs (EC, GFS, Hurr models, etc.).

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I don't know if they neccessarily moved much more west. It looks like they're just more clustered.

Agreed, I actually thought the OP had the timestamps reversed looking at the maps. There are far fewer outliers showing a strike west of the outer banks at 18z than at 12z, with a tight cluster now right over the Outer Banks.

The top 12z image was just changed. I don't know if the other one was in error or not, but I see now what the OP was talking about.

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One of those pieces of guidance (it's either in pink or orange and could be a GFDL run) is doing something with Irene's track which is quite possible offshore Cape Hatteras. As long as the hurricane has a CDO, it should be treated like any other mesoscale convective system. This means that it should ride along any natural baroclinic zone, such as the Gulf stream or the edge of the continental shelf (which becomes a natural baroclinic zone due to vertical mixing in the ocean caused by a hurricane), as long as the mean steering flow is within about 20 degrees of these thermal gradients. Also, as long as it has central convection, it is unlikely to cross 500 hPa height/1000-500 hpa thickness lines, although that can occur north of the Gulf Stream during extratropical transition once (or due to) thunderstorm activity weakening

I don't know if they neccessarily moved much more west. It looks like they're just more clustered.

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Just for fun, here's an E-W cross section of Irene from the AmericanWx WRF model as it passes through the Northern Bahamas. Colors are wind speed, with dark purple 100+ KT. Contours are potential temperature. Model resolution 15 km.

post-35-0-01107800-1314219003.png

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This might be as close as it gets. I think Weather Underground might post something closer to landfall as well.

http://www.weather.g...urge/active.php

You might enjoy looking at this. Click on the map and a zoomable PDF version opens.

http://www2.sunysuff...surge_maps.html

Thanks,I guess Wunderground will eventually add a detailed one for Irene.

http://www.wunderground.com/hurricane/surge_anim.asp

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