Evening QS of Irene

[Derek Ortt]

http://manati.orbit.nesdis.noaa.gov/dat ... MBds99.png

its on the edge, but the flow SE of the axis should be out of the SW if this were a true circ

This is 12.5km. This is not the 25km version that misses centers. Even NHC has indicated that it is likely a wave

[deltadog03]

no LLC on that

[sponger]

I wonder how the mid level circulation is holding together?

[deltadog03]

i think thats what everyone is tracking...

[Sanibel]

This, to me, seems to be arguing a technicality with a well-curved and contained system...

[deltadog03]

but, i had a very hard time finding one today...even on the vis...who knows...

[Sanibel]

This is what I don't understand. I could see a clear west wind spiral going into the center all day on visible. If we were at the same computer I could show it to you.

[gkrangers]

Its not a technicality. A low level circulation is the entire basis of a tropical cyclone.

Also, Derek, its somewhat misleading to say the NHC believes its an open wave. Earlier maybe, but not in the 5PM discussion. They do have trouble discerning where the low level center is...but the discussion is nothing like last night where they mentioned it being a wave, and keeping continuity.

[deltadog03]

derek, i think your quickscat analisys...is correct..dr.lyons just said they can't find a LLC...that the hook was the MLC...good job

[Sanibel]

You misunderstood me gkrangers. I meant the strict Quickscat interpretation could be arguing a technicality when it has already proven to be unreliable. It missed category 4 Iris before and showed an open wave for that hurricane...

[Sanibel]

Not to prolong this Delta, but you have to know what they were using to determine it. Maybe Lyons was offhandedly referring to the Quickscat...

[deltadog03]

true, but honestly could you find a LLC on the vis today?

[Sanibel]

If we were at the same monitor I could point it out. It was the striated lines of clouds curling into the center on the SW edge.

A ship reading would easily solve this.

[deltadog03]

oh, i know...give me a WEST wind and we can call it...lol...i mean, im not saying anything that your saying is not correct...im just relaying what lyons said...and im sure he constantly talks to nhc

[Swimdude]

Ok, a LLC doesn't just GO AWAY, does it? There's still a spin to the storm. And I know this sounds like I have no clue what i'm talking about, which is possibly true... But there's still a spin on the infrared... Doesn't this mean there's still a LLC?

[Stratosphere747]

Ok, a LLC doesn't just GO AWAY, does it? There's still a spin to the storm. And I know this sounds like I have no clue what i'm talking about, which is possibly true... But there's still a spin on the infrared... Doesn't this mean there's still a LLC?

Could easily be a "broad" circulation that is not at the surface.

[Derek Ortt]

a vigorous MLC.

Erin in 1995 had the same type of situation. Dvorak T numbers were 2.5 or 3.0, yet recon kept finding no circ at the surface, but at the 850mb level. It took Erin about 2 days to form a surface circ, same as Claudette in 2003

[Andrew92]

a vigorous MLC.

Erin in 1995 had the same type of situation. Dvorak T numbers were 2.5 or 3.0, yet recon kept finding no circ at the surface, but at the 850mb level. It took Erin about 2 days to form a surface circ, same as Claudette in 2003

I don't entirely remember the environment Erin was in in 1995, but I remember it intensified pretty fast within 24 hours. Not trying to wishcast, especially since I don't live within hurricane territory (Michigan), but is the environment that Irene in going to be similar at all to Erin's?

Just trying to learn here.

-Andrew92

[wxman57]

Ok, a LLC doesn't just GO AWAY, does it? There's still a spin to the storm. And I know this sounds like I have no clue what i'm talking about, which is possibly true... But there's still a spin on the infrared... Doesn't this mean there's still a LLC?

When you're looking down on a storm with satellite, you have to remember that the storm is a 3-D object. The clouds you're seeing on satellite may be tens of thousands of feet above the surface (i.e. a mid-level circulation). You can see a circulation plain as day on satellite but that doesn't mean that the circulation extends all the way down to the surface of the ocean, which is a requirement for a tropical cyclone. Tropical waves can have a very distinct closed circulation visible on satellite, but just a kink in the isobars at the surface.

Satellite interpretation of an LLC is very, very difficult, particularly when the center may be obscured by mid and high clouds and also at night. This was the case with Irene all day and then again tonight.

So, you might have me sit right beside you at your PC and point to a well-defined circulation and I might agree it's there. But you cannot determine if that circulation is 1000 or 5000 feet above the water or if it is at the surface if you cannot see the very lowest level stratus clouds.

That said, sanibel was correct in saying that sometimes QuickSCAT misses circulations, even on systems that have a recon-confirmed circulation. In the case of Irene, it could well have a weak surface spin that's too small for QuickSCAT to pick up.

Wait, news flash... Just got word the NHC upgraded Irene to a TS. I guess they're ignoring the QuickScat and basing the upgrade on banding convection. They've also adjusted the track right a bit more.

[Rainband]

The NHC is the final word