TS Emily: 215 Miles SSE Of San Juan, PR

[Juliancolton]

looks like a serious threat to the NE islands then chances are this recurves away from the US and possible pose a threat to bermuda. Plenty of time watch this one.

Yeah, I'm not seeing the ridge to keep this thing south or west. I still like Hortense 96 as a good analog.

[Scorpion]

Hopefully if it fishes it at least can get the islands. The good trustworthy GFDL says yes

[Srain]

Just remember until we get TC genesis, those hurricane models are nothing more than entertaining imagery and should be taken with a grain of salt.

[Eyewall2005]

oh god, here we go

Here we go with what??

Odds are 1 of those trofs will do the job and set this thing fishing. Main concern is the NE islands were this looks like it will pose a serious threat. All this is just pure speculation on my part. I am to entitled to my own opinion right?

[Avdave]

It depends on when the ridge builds. The SOI spike was only a short lived one, so I'm envisioning the models are pretty decent through Wednesday or so with the weakness off the Atlantic Seaboard. My concern is the track after it lifts north of the Greater Antilles.

Gotcha on the when the ridge builds. That part makes sense to me. You will need to explain to me what the SOI is, I have heard of it but again, I am not a tropical person but trying to catch up here and how it plays into the Tropical scenario.

[VAwxman]

Guys, while not necessarily the most favored solution, we cannot yet rule out a Caribbean cruiser type either. Seems no one really talking about it, but that option is not off the table if it stays weak and farther south, therefore possibly giving it a shot to sneak underneath the day 6 trough that dives off the east coast.

[Avdave]

Guys, while not necessarily the most favored solution, we cannot yet rule out a Caribbean cruiser type either. Seems no one really talking about it, but that option is not off the table if it stays weak and farther south, therefore possibly giving it a shot to sneak underneath the day 6 trough that dives off the east coast.

So if it stays weak and further south, you mean on a line around Barbados, St Lucia, Aruba type of cruiser?

[VAwxman]

So if it stays weak and further south, you mean on a line around Barbados, St Lucia, Aruba type of cruiser?

I'd put it just north of there given that it does look like it is a little more north of where the "center" of the invest was noted on the last suite of hurricane model runs.

[am19psu]

I take it you don't agree with CUMET's post yesterday about northeasterly shear actually causing the dry air to be advected in from the western side of the circulation? If you believe that, it seems that southerly shear would be worse than northerly shear for the advection of dry air from the SAL.

I totally agree with CUMet's post yesterday. That was probably the post of the day. Unfortunately, I don't have access to that level of streamline analysis, so I am just basing my ideas on the empirical research Jason Dunion has been working on. At a first approximation, a shear vector pointing from the dry air disrupts tropical cyclogenesis.

[am19psu]

Gotcha on the when the ridge builds. That part makes sense to me. You will need to explain to me what the SOI is, I have heard of it but again, I am not a tropical person but trying to catch up here and how it plays into the Tropical scenario.

SOI is the Southern Oscillation Index. When the SOI increases over a few days, it usually teleconnects to more ridging along the East Coast in about 10 days. It's not perfect, but it's right more often than not.

[Ed Lizard]

I totally agree with CUMet's post yesterday. That was probably the post of the day. Unfortunately, I don't have access to that level of streamline analysis, so I am just basing my ideas on the empirical research Jason Dunion has been working on. At a first approximation, a shear vector pointing from the dry air disrupts tropical cyclogenesis.

Does the size itself of the system and pouch matter. I'd think the larger system would be less likely to outflow dry air towards the upshear direction enough to really affect the core when the shear isn't particularly strong.

[am19psu]

Guys, while not necessarily the most favored solution, we cannot yet rule out a Caribbean cruiser type either. Seems no one really talking about it, but that option is not off the table if it stays weak and farther south, therefore possibly giving it a shot to sneak underneath the day 6 trough that dives off the east coast.

Agreed. The weak part is the key to that forecast. If it does develop in the next 2-3 days, it will head northwestward.

[am19psu]

Does the size itself of the system and pouch matter. I'd think the larger system would be less likely to outflow dry air towards the upshear direction enough to really affect the core when the shear isn't particularly strong.

Dunion's research hasn't really talked about size much, but I don't see why size would matter. I'd think the inertial stability is the much more important parameter.

[Srain]

The GFS suggests genesis near the 48 hour mark and that model does suggest a more Central Islands threat for now...

[am19psu]

I take it you don't agree with CUMET's post yesterday about northeasterly shear actually causing the dry air to be advected in from the western side of the circulation? If you believe that, it seems that southerly shear would be worse than northerly shear for the advection of dry air from the SAL.

I should also point out that the storm relative stuff is important to CUMet's post yesterday. Again, that's something I'm not going to be able to do. I'd be interested to hear CUMet's thoughts on this.

[Big O]

I would venture a track something like this with the blue line most likely. Intensity, maybe not as strong in the short-term but very intense in the long-term.

Are you implying that this could take an Andrewesque track through south Florida and into the GOM? If it makes it into the GOM will the ridge hold steady or will there be another trough to lift it N and NW?

[wxmeddler]

Are you implying that this could take an Andrewesque track through south Florida and into the GOM? If it makes it into the GOM will the ridge hold steady or will there be another trough to lift it N and NW?

All depends on strength. Its impossible to tell at this point.

[k***]

Andrewesque definitely needs to be added to a list of discouraged ways to describe a disturbance in the MDR

[Scott747]

Andrewesque definitely needs to be added to a list of discouraged ways to describe a disturbance in the MDR

I cringed.

[Bryan Wood]

SOI is the Southern Oscillation Index. When the SOI increases over a few days, it usually teleconnects to more ridging along the East Coast in about 10 days. It's not perfect, but it's right more often than not.

Based on the jump on July 25th and 26th, would this be a possibility next week or is two days too small a time frame for the increase?

[Srain]

Looks like some tasking is in the pipeline for 91L. Good to see a G-IV mission as well...

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

1005 AM EDT FRI 29 JULY 2011

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 30/1100Z TO 31/1100Z JULY 2011

TCPOD NUMBER.....11-059 AMENDMENT

I. ATLANTIC REQUIREMENTS

1. NEGATVIE RECONNAISSANCE REQUIREMENTS.

2. OUTLOOK FOR SUCCEEDING DAY:

A. INVEST SUSPECT AREA AT 31/1800Z NEAR 14.0N 54.0W.

B. ADDED....A G-IV MISSION FOR 01/0000Z.

3. REMARK: P-3 MISSIONS FOR 29/1200Z AND 30/0000Z

CANCELED BY NHC AT 28/2345Z.

[am19psu]

Based on the jump on July 25th and 26th, would this be a possibility next week or is two days too small a time frame for the increase?

That's the million dollar question. I don't have a good answer for you. My guess is that we'll see more ridging than currently indicated, but I don't know how much.

[EasternUSWX]

This thing is huge.

http://www.ssd.noaa.gov/goes/flt/t2/flash-vis.html

[CUmet]

I should also point out that the storm relative stuff is important to CUMet's post yesterday. Again, that's something I'm not going to be able to do. I'd be interested to hear CUMet's thoughts on this.

Mike Montgomery's pouch site a dividing streamline analysis for each pouch, although admittedly it's difficult to interpret. What's easier to interpret for me are the wind vectors, which I believe are the ones that are used for calculating the streamlines. The description of the product is here.

The original paper associated with this is here: Riemer and Montgomery (2010)

What Riemer and Montgomery (2010) show is that the pouch is distorted in the presence of shear, which make the TC vulnerable to dry-air intrusions. In their simulation, they had a TC undergoing easterly speed shear, so easterly storm-relative upper-level winds with westerly storm-relative low-level winds. Hence, you get inflow into the western quad, and doing back trajectories (Fig. 6 in the paper) shows that the dry air intrusion is *most effective* when it originally located downshear-right. However, the magnitude of the dry-air intrusion into the TC depends on moisture gradient, the vertical profile of moisture, and the vertical profile of winds...so it *can* come from elsewhere.

My interpretation of this is that it doesn't necessarily contradict Dunion's work. The dry air doesn't just travel inwards towards the TC, but it also gets advected counterclockwise around the TC. It may be that if you see dry air upshear of the TC, the Riemer and Montgomery processes described above may have already been underway for some time.

I do think it's either inaccurate or misleading to say that the shear vector is "advecting" the dry air into the TC. From what I've read on the topic, it's more complicated than that.

[GaWx]

The 12Z Euro is totally unimpressed through 72 hours. However, this may mean that it stays weaker and on a more westward track into the Caribbean and potentially the GOM (assuming it ever actually beomes a TC).

[am19psu]

Mike Montgomery's pouch site a dividing streamline analysis for each pouch, although admittedly it's difficult to interpret. What's easier to interpret for me are the wind vectors, which I believe are the ones that are used for calculating the streamlines. The description of the product is here.

The original paper associated with this is here: Riemer and Montgomery (2010)

What Riemer and Montgomery (2010) show is that the pouch is distorted in the presence of shear, which make the TC vulnerable to dry-air intrusions. In their simulation, they had a TC undergoing easterly speed shear, so easterly storm-relative upper-level winds with westerly storm-relative low-level winds. Hence, you get inflow into the western quad, and doing back trajectories (Fig. 6 in the paper) shows that the dry air intrusion is *most effective* when it originally located downshear-right. However, the magnitude of the dry-air intrusion into the TC depends on moisture gradient, the vertical profile of moisture, and the vertical profile of winds...so it *can* come from elsewhere.

My interpretation of this is that it doesn't necessarily contradict Dunion's work. The dry air doesn't just travel inwards towards the TC, but it also gets advected counterclockwise around the TC. It may be that if you see dry air upshear of the TC, the Riemer and Montgomery processes described above may have already been underway for some time.

I do think it's either inaccurate or misleading to say that the shear vector is "advecting" the dry air into the TC. From what I've read on the topic, it's more complicated than that.

Thanks, man. I definitely appreciate the input. Hopefully I'll get to the paper here in a bit.

[Cheeznado]

The 12Z Euro is totally unimpressed through 72 hours. However, this may mean that it stays weaker and on a more westward track into the Caribbean and potentially the GOM (assuming it ever actually beomes a TC).

Interestingly enough the 12Z GFDL, which was developing this into a hurricane, has completely reversed and now looks like the 12Z Euro, weak LP into the Islands in about 4 days.

[wxmx]

Could miss the trough, and is a lot better looking @ day 5 ... Caribbean cruiser?

[Big O]

I cringed.

I said an Andrewesque track, not intensity.

[wxmx]

Another important teleconnection is the -NAO/-AO, which would favor either a close recurve or a Caribbean/GOM track.