Alex Advisories

[soonertwister]

THEY "DIDNT FIND" 50KTS... IT WAS AN OBSEVATION VISUALLY... NOT ACCURATE... FLIGHT LEVEL WAS STILL 45KNT.. AND THE SURFACE WIND IS ABOUT 80% OF THAT AT THE SURFACE...

When they observe surface winds from low altitude they look for a specific set of visual clues that vary depending on surface wind speed. Obviously they felt that the surface wind was greater than the flight level wind or they would not have reported it to be higher. And when flight level is well below 1500 feet, the standard formula of -20% doesn't necessarily apply.

For instance, they can observe the wave height and choppiness of the seas, and the amount of spray off the wave caps and how quickly and far it blows. These guys aren't rookies you know. This is what they do for a lving.

[Stormchaser16]

Its not in the pacific.......

The fact of the matter is- an LLC is Underneath signifigant convection, and is becoming much better organized.... the pressure has dropped throughout the day from when they had it at 40MPH before with 1010MB, now its down to 1007...... you are right about the 50KT observation, we are not sure where that came from. However if i converted that correctly, 36 KTS would be around 40MPH yes? In the atlantic we call that a TS yes?

[ameriwx2003]

The 11 PM discussion on ALEX is a good read and explains why Alex looks more organized then it really is...:)


http://www.storm2k.org/ham/hw3.php?conf ... hwvmetric=

[Derecho]

Speaking of things that confuse people, I have to add the infamous line "D" in VORTEX reports.

From hurricanehunters.com:

"D. ESTIMATE OF MAXIMUM SURFACE WIND OBSERVED IN KNOTS. 65 kt means the highest estimated surface wind is 65 knots on this particular inbound leg. The flight meteorologist looks at the sea surface and can estimate how strong the winds are by what the sea looks like. At particular wind speeds, the sea begins to form white caps, then patches of foam, then some of the foam patches begin to appear green, etc. The key word here is "observed"; the meteorologist may not see the highest surface winds because of darkness, heavy rain or clouds, so often this number is lower than the maximum flight level wind. A "knot" is a nautical mile (nm) per hour. To convert to miles per hour, use 1.15 miles/nm; 65 nm/hr x 1.15 mi/nm = 75 miles per hour. To convert to meters per second, cut knots in half: 65 kt = 33 m/s. If not observed at all, this block is reported as NA (Not Applicable)."


So it's a guy leaning out the window GUESSING the wind speed based on what the waves look like.

And it's about as accurate as it sounds. It rarely factors into NHC thinking on an advisory.

Flight level winds are far more accurate.

[Stormchaser16]

Exactly sooner- this is why the 11PM advisory should have at least reflected some of what they found..... I would have thought 45MPH would have been a reasonable upgrade, given that they had it at 40MPH before with 1010MB, now we are down to 1007MB, and a very nice SAT/IR presentation

[Derek Ortt]

yeah, and it was dark.

Everyone in the field knows that the estimates are just that and are subject to large error

but 40kT is still quite possible

[Three Blind Mice]

look at the wind fields. Thats why I called it a fish storm. Look at the current winds on the coast of GA SC. Unless we get Stewarts move to the north quickly(next 24) then this is a fish storm.

[wxman57]

Careful, the center is not beneath that convection, it's still exposed to the north. Cirrus is moving north over the center, though, a sign of decreasing shear. Here's the latest position with respect to the convection to the south. Note that some storms are building north toward the SE side of the low, definitely a sign of diminshing shear:

<img src="http://myweb.cableone.net/nolasue/alex15.gif">

[WXBUFFJIM]

I still think the intensity forecast is a bit low also, but a big improvement from earlier tonite. The official forecast makes this 50 knots with gusts to 60 knots near hatteras and Okracoke Island. I still suspect we may go 60 knots with gusts over hurricane force possible in this region later tomorrow night into Tuesday morning. If the shear lessens more so than anticipated, we may have a period of rapid deepening near the outer banks later tomorrow. That's the thing I'm worried about, not just the rip current/heavy rain issue. Rapid deepening over the gulf stream is not a good thing and it's a dangerous place for that to happen.

Jim

[vacanechaser]

Whats with all caps?

I still would have given it at least 45MPH winds in the 11PM advisory just based on the way the system has signifigantly organized. They should have reflected at least a part of what the recon. seemed to have found

sorry about the caps... i had it locked when i updated the site and just didnt feel like changing it after i typed the message.. lol.. lazy...

you just cant base the wind increase based on how it looks.. apperantly hr didnt feel it was an accurate ob.. stewart is one of the bst there and he usually gets attacked because he over does things sometimes... everytime we talk with him, he says he likes to see the convection continue over a period of time... i am sure that if it is still looking the same in the morning, you can expect 50mph..

[Derecho]

Its not in the pacific.......

you are right about the 50KT observation, we are not sure where that came from.

We know EXACTLY where it came from. It's the visual wave guesstimate. And they'll go with adjusting FL winds downward EVERY time over the line D visual estimate, because visual estimation flat out isn't accurate.

[Stormchaser16]

Well that discussion IS pretty good, however i have not seen anymore LLC's pop out of the convection, one main one now sits underneath the northern edge of the convection......

Also derecho- I think its a little more then guessing, however i can see why they would not upgrade based upon it, however it would probably have been a good idea to have split the difference

[wxman57]

Its not in the pacific.......

The fact of the matter is- an LLC is Underneath signifigant convection, and is becoming much better organized.... the pressure has dropped throughout the day from when they had it at 40MPH before with 1010MB, now its down to 1007...... you are right about the 50KT observation, we are not sure where that came from. However if i converted that correctly, 36 KTS would be around 40MPH yes? In the atlantic we call that a TS yes?

Actually, that's not correct - yet. The LLC is north of the heavier convection. Don't let cirrus fool you on IR imagery. There are a few storms beginning to rotate northward toward the SE part of the center, however.

<img src="http://myweb.cableone.net/nolasue/alex15.gif">

[Stormchaser16]

Good point vacane- i definately would have not gone with 50MPH however given the pressure drop and consolidated convection over the LLC, 45MPH is what i would have expected

I know that is where it came from Derecho- however the point was that, we dont know for how long of a time period that was based over.....

[wxman57]

Its not in the pacific.......

The fact of the matter is- an LLC is Underneath signifigant convection, and is becoming much better organized.... the pressure has dropped throughout the day from when they had it at 40MPH before with 1010MB, now its down to 1007...... you are right about the 50KT observation, we are not sure where that came from. However if i converted that correctly, 36 KTS would be around 40MPH yes? In the atlantic we call that a TS yes?

Actually, that's not correct - yet. The LLC is north of the heavier convection. Don't let cirrus fool you on IR imagery. There are a few storms beginning to rotate northward toward the SE part of the center, however.

<img src="http://myweb.cableone.net/nolasue/alex15.gif">

[Derecho]

Well that discussion IS pretty good, however i have not seen anymore LLC's pop out of the convection, one main one now sits underneath the northern edge of the convection......

Also derecho- I think its a little more then guessing, however i can see why they would not upgrade based upon it, however it would probably have been a good idea to have split the difference

From 6+ years of looking at VORTEX reports I can tell you the visual estimate is basically ignored ALL of the time, if it conflicts with measured winds.

Which leads to the valid question of why they bother with it; 1) it's likely a holdover from an earlier time and 2) if their equipment fails at least they've got SOMETHING reported.

[WXBUFFJIM]

Definitely a sign of some intensifying. The time I'd be worried about is later tomorrow as this thing makes a B line towards Hatteras. A period of rapid deepening is possible if shear lessens more so than expected now. It's definitely got potential to be 50-60 knots with gusts above hurricane force on the outer banks later tomorrow and tomorrow night. Drumm Inlet, which was hit by Isabel last year definitely is no stranger to tropical storms or hurricanes. We'll definitely have to monitor this throughout the next 24-36 hours. After 48 hours, southwesterly shear should cap intensification as this thing moves away from the Outer Banks.

Jim

[The Dark Knight]

Same here...

[Stormchaser16]

http://www.ssd.noaa.gov/PS/TROP/DATA/RT ... -loop.html

wxman- yes its still on the northern side, however on IR it does look like the convection is coming over the LLC

[ameriwx2003]

The 11 P.M. discussion also states this

Some significant strengthening could occur Monday and Monday
night as alex begins to move northeastward and passes over the
gulfstream under decreasing vertical shear

The next 24 hours should be interesting:):)