ATL: DANNY - Remnants - Discussion

[TropicalAnalystwx13]

Steering should be comfortably west-northwest over the next few days regardless of strength with the mid-level ridge to the north of Danny.

[TheBurn]

Was in Puerto Rico this summer and they are having a heckuva drought, would be great if they caught just the edge of it for some much needed rain

Where's the "Like" button?

[tatertawt24]

Even if it falls apart in true Atlantic fashion, it overachieved in my opinion. Proud of it!

[Bocadude85]

Danny looks like a little buzzsaw.

http://www.ssd.noaa.gov/PS/TROP/floaters/04L/imagery/vis_lalo-animated.gif

[Sanibel]

Might get an unexpected boost past 55* from favorable SST's.



There's a dry but present southern inflow (sign of potential).


I can see why they were saying 100mph. Don't underestimate this thing because of size. Zoom on this and you'll see some serious hurricane behavior.

[tatertawt24]

At 12:45 UTC it looked like a really tiny version of Bret (1999).

[ozonepete]

One question.

The
initial intensity of 65 kt is based on NHC objective Dvorak
classifications of T4.1-T4.2 using an eye feature.

What does this mean? Modified ADT?

I think the NHC means they're using TAFB and SAB estimates, both of which use an objective Dvorak technique. I don't know why TAFB and SAB come up with different numbers sometimes; probably slightly different input data, but one of the pro mets here probably knows. I'll look into it. Anyway, modified Dvorak techniques, such as CIMSS' ADT (Advanced Dvorak Technique) gets the original objective technique number and then runs additional algorithms to adjust the number for things the original technique doesn't always handle well. Your question is interesting, because while NHC's simpler method got 4.1 or 4.2, CIMSS' current ADT number is 3.1 which is clearly too low. But their analysis page shows they analyzed it without noting the eye so that's one reason they're way off. We will see how soon they catch it since they run every hour.

[StarmanHDB]

Little Danny looks like it's about to make its final punch out of the moisture laden ITCZ. It'll be very interesting to see what happens from here. Will Danny's tiny moisture envelope be able to sustain any convection amongst that huge mountain of dry air which it's about to encounter?

[gatorcane]

pretty impressive little Hurricane (almost an oxymoron) actually I must admit. Is this setting the record for the smallest hurricane in the Atlantic MDR?

[Gustywind]

Danny Has Intensified Rapidly into a Hurricane

Aug 20, 2015; 11:11 AM ET Danny, a very small tropical cyclone has attained hurricane strength and should remain a hurricane for the next few days as it moves towards the Leeward Islands.

http://videowall.accuweather.com/detail ... Start=true

[Yellow Evan]

One question.

The
initial intensity of 65 kt is based on NHC objective Dvorak
classifications of T4.1-T4.2 using an eye feature.

What does this mean? Modified ADT?

I think the NHC means they're using TAFB and SAB estimates, both of which use an objective Dvorak technique. I don't know why TAFB and SAB come up with different numbers sometimes; probably slightly different input data, but one of the pro mets here probably knows. I'll look into it. Anyway, modified Dvorak techniques, such as CIMSS' ADT (Advanced Dvorak Technique) gets the original objective technique number and then runs additional algorithms to adjust the number for things the original technique doesn't always handle well. Your question is interesting, because while NHC's simpler method got 4.1 or 4.2, CIMSS' current ADT number is 3.1 which is clearly too low. But their analysis page shows they analyzed it without noting the eye so that's one reason they're way off. We will see how soon they catch it since they run every hour.

Normally TAFB/SAB numbers are considered "sbujective" in NHC bulletins and ADT numbers are "objective". My guess is that this is internal ADT. As you said, it's not uncommon for TSFB/SAB to get different numbers, and FYI, it's an issue in other basins as well (in the West Pacific, SAB and JTWC often give different numbers.

[TropicalAnalystwx13]

One question.

The
initial intensity of 65 kt is based on NHC objective Dvorak
classifications of T4.1-T4.2 using an eye feature.

What does this mean? Modified ADT?

I think the NHC means they're using TAFB and SAB estimates, both of which use an objective Dvorak technique. I don't know why TAFB and SAB come up with different numbers sometimes; probably slightly different input data, but one of the pro mets here probably knows. I'll look into it. Anyway, modified Dvorak techniques, such as CIMSS' ADT (Advanced Dvorak Technique) gets the original objective technique number and then runs additional algorithms to adjust the number for things the original technique doesn't always handle well. Your question is interesting, because while NHC's simpler method got 4.1 or 4.2, CIMSS' current ADT number is 3.1 which is clearly too low. But their analysis page shows they analyzed it without noting the eye so that's one reason they're way off. We will see how soon they catch it since they run every hour.

I was more reading it as the forecasters on shift did their own Dvorak classification, factoring in the eye scene. SAB was T3.0/45kt at 1145z, and TAFB was T3.5/55kt. Both too low.

[Bocadude85]

Perhaps Danny has ingested some dry air?

http://www.ssd.noaa.gov/PS/TROP/floaters/04L/imagery/rb_lalo-animated.gif

[Sanibel]

That southern inflow should trade maintaining intensity for dry air. It has already intensified in an area where it was zapped by dry air. SST's only get better from here.

[Raebie]

Relatively significant movement north?

[NCSTORMMAN]

Perhaps Danny has ingested some dry air?

http://www.ssd.noaa.gov/PS/TROP/floaters/04L/imagery/rb_lalo-animated.gif

Doesn't look like it to me. Dry air is well to the north and I think it is just spreading the convection out. Next few frames will tell the tale. Now I will head back to coding a new web application :+)

[Sanibel]

GFDL weakens it as it approaches the islands but then strengthens it north of the islands.

[Yellow Evan]

I think the NHC means they're using TAFB and SAB estimates, both of which use an objective Dvorak technique. I don't know why TAFB and SAB come up with different numbers sometimes; probably slightly different input data, but one of the pro mets here probably knows. I'll look into it. Anyway, modified Dvorak techniques, such as CIMSS' ADT (Advanced Dvorak Technique) gets the original objective technique number and then runs additional algorithms to adjust the number for things the original technique doesn't always handle well. Your question is interesting, because while NHC's simpler method got 4.1 or 4.2, CIMSS' current ADT number is 3.1 which is clearly too low. But their analysis page shows they analyzed it without noting the eye so that's one reason they're way off. We will see how soon they catch it since they run every hour.

I was more reading it as the forecasters on shift did their own Dvorak classification, factoring in the eye scene. SAB was T3.0/45kt at 1145z, and TAFB was T3.5/55kt. Both too low.

With non-automated Dvorak, T-numbers come in either whole numbers or .5's, so probs not.

[wjs3]

One question.

The
initial intensity of 65 kt is based on NHC objective Dvorak
classifications of T4.1-T4.2 using an eye feature.

What does this mean? Modified ADT?

I think the NHC means they're using TAFB and SAB estimates, both of which use an objective Dvorak technique. I don't know why TAFB and SAB come up with different numbers sometimes; probably slightly different input data, but one of the pro mets here probably knows. I'll look into it. Anyway, modified Dvorak techniques, such as CIMSS' ADT (Advanced Dvorak Technique) gets the original objective technique number and then runs additional algorithms to adjust the number for things the original technique doesn't always handle well. Your question is interesting, because while NHC's simpler method got 4.1 or 4.2, CIMSS' current ADT number is 3.1 which is clearly too low. But their analysis page shows they analyzed it without noting the eye so that's one reason they're way off. We will see how soon they catch it since they run every hour.

Hey Ozonepete. It is interesting and the NHC is ALWAYS careful to call out TAFB and SAB when they provided the T number. I interpreted this as the NHC did their own quick object scoring using an eye pattern (the eye had JUST popped up during the time the 11 AM package would have been written) whereas the other T numbers might have used non-eye pattern (since there wasn't a visible or IR eye at that time). Said differently, the eye popped out as the package was being written so the NHC ran its own classification (perhaps just by walking over to TAFB and having the analyst rework it using the eye pattern). I'll see what I can find out.

[Gustywind]

AN IMPRESSIVE PHOTO OF HURRICANE DANNY FROM SPACE

https://pbs.twimg.com/media/CM3KyxOU8AAeDee.jpg:large