ATL: ISAAC - Post-Tropical - Discussion

[ConvergenceZone]

KWT, if this is true, why were the NHC discussion writeups yesterday and the weather
channel yesterday stating that due to the large circulation, strengthening
should be slow? What has changed between yesterday and today regarding the
circulation? just curious.

Take a look at Wxman57's post above, it covers it all very nicely. I'd say probably the main factor is the shear which has helped to drive the moderate dry air into the system and really cause that lop-sided look it had this morning. It does seem to have shaken that off to some extent but its still got a way to go.

Hmm, that's interesting. It is strange how it went from such a large circulation
to such a small circulation in 24 hours......
Even though this may end up being a non wind event. Plenty of rain
and tons of inland flooding likely from Isaac.

[HurrMark]

I'm surprised that Isaac remains only a tropical storm considering the time it's been over very warm water. I expected disruption and delayed intensification from Cuba and Haiti, but I, and most folks, it seems, expected that the storm would become a hurricane given the very warm water and only light-moderate shear. As I'm sure we all know, we have comparatively less skill forecasting intensity (compared to track). Even if Isaac went through a period of rapid intensification, I think it's quite unlikely it would be any worse than a Cat 2 at landfall. It *could* be worse (Bastardi seems to make sure to mention how it could be worse -- see 960 mb by yesterday or Cat 5 by landfall), but it could also not intensify much further and make landfall as a Cat 1.

Note that the big surge producers tend to (a) be large in size and (b) have come from storm that previously had been Cat 4 or Cat 5. Katrina was only Cat 3 at main landfall IIRC, but it was carrying it's massive surge accumulated from the time it had been a Cat 5. Again, we're not very good with intensity forecasting, so this post gets the usual "caveat emptor" as any other post discussing intensity forecasts.

I don't get it either...I have seen plenty of storms with much worse conditions intensifying. There have been studies that have stated that global warming may actually be a negative factor on hurricanes because of greater shear, but I don't know if I should take that with a grain of salt. The fact that we have not had a major hurricane hit US soil in seven years, and it appears the streak will continue (and my guess is into next year as El Nino starts to rage in September) is quite telling. Anyway, another topic for another time. I do believe it is still intensifying, albeit at a slow rate. And I still think it could make 105-110 at landfall.

[drezee]

Buoy 42003:
9:47 am 988.7 mb
with 37kt 1-min sustained winds pressure maybe lower maybe 985

[mutley]

Could Isaac be disassociating itself from that big band of convection over the east coast of Florida? And could that be hindering intensification? It looks like that band is never going to make it to the west coast of Florida.

[Sanibel]

That detached band over Florida tells you it isn't pulling everything in. I still say it will though.

[rainstorm]

i suppose this will be another one of those gom TS's that appear to deepen as it goes onshore due to friction. im guessing the best isaac will ever look is after its left the water.

i wonder if isaac would have done better had it went east of florida toward NC? the GOM has been a pretty dead zone for a long time now.

[AdamFirst]

Treasure coast getting shellacked by one of the last major feeder bands

NWS Melbourne confirmed tornado touchdown in Indian River County - 20+ mobile homes damaged, other structures damaged. Major flooding is occurring areawide.

Weather this morning was worse than all day yesterday

[drezee]

update on 42003:
10:46 am 987.7 mb
maybe in SW part of eye...light winds...

[jabman98]

With people suggesting Isaac could be more of a rain/flooding issue than a wind issue, wondering how saturated the ground is already where Isaac is projected to go. I think Louisiana has had a rainy summer, right?

Also, is Isaac projected to get to any of the drought-stricken areas? They sure could use the rain.

[tolakram]

Some loops.

Bookmark this page to always see the latest images: http://www.ssec.wisc.edu/data/1min/index.php

Longer loop, through 16:11Z, 12:11PM EDT: http://www.ssec.wisc.edu/data/1min/inde ... height=800

[midnight8]

For those with Ham radio or shortwave radio capabilities I got the following email reguarding Isaac from ARES today.

FYI --

Tropical Storm ISAAC's Emergency Net Frequency


With the latest storm predictions having TS ISAAC's
making landfall in the Greater New Orleans area at
a late Tuesday/early Wednesday time frame now --

The ARRL Delta Division (AR, LA, MS & TN) will
activate the Delta Division Emergency Net tomorrow
evening (Tuesday, August 28th) at 1800 CDT (6 PM)
local time, on 3.890 MHz. Initial Net Control is
to be WB5LHS operating from the Louisiana Governer's
Office of Homeland Security & Emergency Prepardness
in Baton Rogue, LA


Stations outside of the affected area are well advised
to monitor *only* -- Do *not* transmit unless asked to
do so by Net Control.

72/73 John Moore, KK5NU

[rtd2]

"THE INITIAL MOTION ESTIMATE IS 305/12. NO SIGNIFICANT CHANGE WAS
MADE TO THE PREVIOUS FORECAST TRACK. THE LATEST 12Z UPPER-AIR DATA
INDICATE 20-40 METER HEIGHT RISES AT THE 500 MB AND 400 MB LEVELS
ACROSS THE SOUTHEASTERN AND SOUTH-CENTRAL U.S....WHICH SUGGESTS
THAT THE SUBTROPICAL RIDGE TO THE NORTH OF ISAAC HAS STRENGTHENED
SLIGHTLY".

This part of the disc is slightly interesting.....

What will this do to the storm?

Stair Stepping ...no straight lines

[tolakram]

Another look at the heat potential.

[wxman57]

Now that the wind field is shrinking how long does the increased storm surge from the prior large wind field stay with Issac? Is it safe to assume that given the proximity to landfall that the increased threat of a higher storm surge will still be present even if Issac tightens up to a much smaller wind field?

it's the size of the stronger wind fields that determines max surge. Currently, Isaac has a very small area of stronger winds. That should be the case at landfall as well. SLOSH indicates about 5-8 feet into SE LA as an average-sized Cat 1, but Isaac will be a bit smaller than average as far as its 58 and 74 mph wind field at landfall.

[tolakram]

And a Flash loop, 1 minute imagery: http://www.ssec.wisc.edu/~rabin/goes14/loop_srso.html

[PTPatrick]

If GFS comes true it could be drought buster for the mid ms valley moving slowly through Arkansas and eventually MO and IL then the OH valley....that's NOT a bad thing

[otowntiger]

That detached band over Florida tells you it isn't pulling everything in. I still say it will though.

That detached band over eastern FL pennisula is pulling away toward the north and east isn't it?

[rtd2]

interesting ...morning started off sunny blue skies calm but about 30 min ago. Winds have pick up from nothing to 5-10 sustained and 20-25mph gust weird Im about 17 miles north of Biloxi..elevation 117 feet Above sea level

[wxwatcher1999]

Maybe I'm wrong but I just don't see how it could go east of NO unless it starts moving more north real soon?

[tolakram]

Latest.



Looking top down (corrected) it's easier to see how the inner part of the storm is doing well wrapping convection around. it also has the appearance of shifting west (missing frames). Not sure how to read that jump, might be an illusion.

Java Required: http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... mframes=25