Tropical Storm Gordon,Analysis,Sat Pics,Models Thread

[Scorpion]

Interesting NHC discussion tonight. I for one am not buying the recurving idea just yet.

[fci]

I think that the NHC is just being careful in the discussion since the models have pretty much ignored the system.

After they latch on I would suspect a consensus of the recurvature.

[wxmann_91]

Actually, the weakness is pretty deep and powerful and remains through 72 hr...

http://www.nco.ncep.noaa.gov/pmb/nwprod ... v_072m.gif

Afterwards, the gap closes, and if by then, for some reason, Seven has not recurved yet, we'll have to watch this closely.

[orion]

Interesting NHC discussion tonight. I for one am not buying the recurving idea just yet.

According to the discussion, I'm not sure they are buying it either. A lot of IFs still out there with this one. I do think it will recurve, but I'm thinking west of the NHC track.

[Josephine96]

any chance of it getting close to the SE?

[CrazyC83]

Right now I give it a 55% chance of recurving, 30% chance of keeping west to the East Coast and 15% chance of quick dissipation.

[Josephine96]

I'll go 50 percent curve, 35 percent East Coast, 15 percent doesn't survive..

[WxGuy1]

Let's take a look at some mean level winds to get an idea where TD7 will and won't go. I've made 3 mean 400-700mb streamline graphics, indicating the position of TD 7 on each graphic with yellow arrows indicating steering currents in its path.

Don't sound so disappointed (some of you) that this developing storm won't likely affect any land areas.

Excellent -- thanks for providing those maps! It'd be nice to see more maps such as those posted on here, so as to help alleviate and/or prevent the "my hunch is that this will miss the 'weakness in the ridge' and head towards the US" comments. It would be very difficult for TD7 to work 180 degree against the steering current (maybe bordering on impossible depending upon how you define the steering current -- i.e. the direction of travel definition would mean it is impossible, by definition, of going 'against' it).

Now, there is one minor complication. Notice how close the cyclone is to the pseudo stagnation point / center of the COL to the immediate WNW of TD7. This col is characterized by a low to the north (Florence), an inverted midlevel trough to the south, a high over the northwestern Caribbean, and a high ENE of Bermuda over the central Atlantic (using geostrophic flow, I'm assuming the streamlines are parallel to isohypses / lines of constant height)... We see nearly textbook deformation just west of TD7, with the axis of contraction largely in a WNW-ESE alignment and the axis of dilatation in a NNE-SSW alignment. If the cyclone can drop southward a bit, streamline analysis indicates that it would be recurved to the southwest instead of the northeast (it'd be on the equatorward side instead of the poleward side of the stagnation point / center of the col). In the first graphic, it looks like the flow just 5 degrees south of TD7 will end up being deflected southward, while TD7 itself looks to be deflected northward. As Florence moves away, this point will move west-northwestward with time.

Fortunately for those who are looking to avoid a storm hitting the US, it appears as though TD7 will be on the poleward side of the col / stagnation point, thereby allowing it to recurve out to sea.

[boca]

Now that we in Sept the troughs get a little stronger which tend to turn storms poleward like Florence. I think the only area which should be concerned about TD7 is Bermuda after they get smacked by Florence. I think the way the pattern is the only way the states will get hit is from the Gulf or Caribbean Sea which I'm not putting to much stock into that happening this year and yes its just my opinion so don't jump on me because its still September but I don't see anything major this year and I hope I'm right for us to recoup from 04 and 05.

[Matt-hurricanewatcher]

On strength...Cimss shear maps show 3-5 knots over the system at the upper levels, with very little at the mid levels. Also the upper low at 24 north/58 west. The stream of clouds racing northward ahead of it. It is moving westward at about 10 knots. This is forming a Anticyclone right over the cyclone, even so there is some shear at the very high levels...Pushing some cirus to the southeast...But overall this thing is becoming organized well through out the last few hours.

So we got a ULL moving westward. Which is northwest of the cyclone...This helps form a outflow jet. Also this helps form a developed Anticyclone. What needs to be watched is how the LLC and central dense gets along. So far they are ontop of each other. The Cdo is round=little shearing.

I see no reason with current developments, that this could not go on to be a respectable storms.

0 30 knots
6 35 knots
12 40 knots
24 50 knots
36 60 knots
72 70 knots
96 85 knots

This is assuming in the later part, that things remain faverable. In which can change.

[BatzVI]

I find this interesting....from the 805 discussion:

THE TROPICAL WAVE ALONG 54W AND ASSOCIATED SURFACE LOW NEAR 21N
IS DISCUSSED IN THE SPECIAL FEATURES SECTION. GUIDANCE AND
RECENT SATELLITE PICTURES SUGGEST THIS WAVE MAY BE SPLITTING.
THE LOW IS FORECAST TO MOVE W THEN NW IN THE WAKE OF
FLORENCE...AND THE SRN PORTION OF THE WAVE IS EXPECTED TO
GRADUALLY PUSH W THROUGH THE TRPCL ATLC AND INTO THE ERN
CARIBBEAN THROUGH MIDWEEK. ONLY ISOLATED SHOWERS/TSTMS ARE
CURRENTLY NOTED S OF 16N WITHIN 200NM OF EITHER SIDE OF THE AXIS.

[Epsilon_Fan]

these storms have been fairly unremarkable... now this new one is just going to follow Flo out to sea. Where's the drama? I guess we are all glad it has panned out like this so far but maybe deep down a little bored...

[gilbert88]

Unremarkable was normal until 1998.

[orion]

Now, there is one minor complication. Notice how close the cyclone is to the pseudo stagnation point / center of the COL to the immediate WNW of TD7. This col is characterized by a low to the north (Florence), an inverted midlevel trough to the south, a high over the northwestern Caribbean, and a high ENE of Bermuda over the central Atlantic (using geostrophic flow, I'm assuming the streamlines are parallel to isohypses / lines of constant height)... We see nearly textbook deformation just west of TD7, with the axis of contraction largely in a WNW-ESE alignment and the axis of dilatation in a NNE-SSW alignment. If the cyclone can drop southward a bit, streamline analysis indicates that it would be recurved to the southwest instead of the northeast (it'd be on the equatorward side instead of the poleward side of the stagnation point / center of the col). In the first graphic, it looks like the flow just 5 degrees south of TD7 will end up being deflected southward, while TD7 itself looks to be deflected northward. As Florence moves away, this point will move west-northwestward with time.

Thanks to wxman57 for the graphics and to wxguy1 for the further info. I apologize if I am missing something obvious here, but what is COL? Trying to learn and that is new to me... thanks!

[all_we_know_is_FALLING]

I like how we have a TD and a hurricane in the Atlantic and still a relatively small number of members here. I guess since they aren't major threats to the US that would explain it.

Anyways.. onto TD7. It's still too early to make a confident forecast, but I think a curve out to sea or a possibly storm along the Eastern Seaboard looks most likely. Of course, nothing should really be ruled out yet, and anything can happen.

[CrazyC83]

Yeah we have so few here that it is hard to keep the Recon on Florence updated...we all seem to have different views on TD7 right now.

[Matt-hurricanewatcher]

Tropical depression 7 convection kills the cane. This thing is getting closer to a tropical storm if not one.

[southerngale]

I like how we have a TD and a hurricane in the Atlantic and still a relatively small number of members here. I guess since they aren't major threats to the US that would explain it.

Anyways.. onto TD7. It's still too early to make a confident forecast, but I think a curve out to sea or a possibly storm along the Eastern Seaboard looks most likely. Of course, nothing should really be ruled out yet, and anything can happen.

There was a thread about that recently. This was my post in there:

And as to the first post of this thread, it should be common sense that if there is a potential for landfall, more people will be interested/concerned. I see some of the same faces (well, names) here every day...those are generally the "weather freaks" as I call them. I've been called that all my life as well. Anyway, those are the ones who will likely watch/track any TS/cane, give or take a few stragglers. That doesn't mean there will be more posts (see Frick's post above).

But to act like it's a shocking event that many people only care if it has the potential to make landfall is crazy, IMO. Of course the average person cares more if it could make landfall near them or near people they know. This is to be expected and seems so logical to me. MOST people aren't interested in weather that will never affect them and MOST people use Storm2k as a resourceful tool when something *could* potentially affect them.

Most people don't care about weather in the middle of an ocean.

[all_we_know_is_FALLING]

Oh. I read that thread.. haha.

I wasn't shocked that there wasn't as many people as there was during previous storms, just surprised that there were so few people. But, then again, it's late at night and such and such.


Anyways, what are the chances of TD7 affecting Bermuda? That would be interesting and bad for them, to have two systems so close together.

[WxGuy1]

Thanks to wxman57 for the graphics and to wxguy1 for the further info. I apologize if I am missing something obvious here, but what is COL? Trying to learn and that is new to me... thanks!

A col refers to a specific upper-level pattern... Imagine a 2x2 box, with a Low in the upper-level and lower-right corners, and a high in the upper-right and low-left corners:

L ||| H
----- -----
H ||| L

OR

H ||| L
----- -----
L ||| H

In this arrangement, the fluid (air) at the center of the pattern has zero motion (i.e. it's calm). The remainder of the flow can be imagined by thinking about the direction of flow expected given the height gradient. For example, in the first/top example, there will be westerly flow between the L and H on the left half of the pattern. Imagine putting a balloon in this area... It will move eastward until it nears the vertical lines. In the top part of the box, there is southerly flow between the L to the left and the H to the right; in the bottom part of the box, there is northern flow between the H to the left and L to the right. So, where will the balloon go? It depends upon whether it is just above the middle line or just below the middle line. If it's just above the middle line, it'll eventually be turned northward with the southerly winds; if it's just below the line, it'll eventually be turned southward with the northerly winds. Technically, if it's right on the line, it'll decelerate as the velocity approaches 0, and it'll get "stuck" in the middle. From a deformation standpoint in the top example, the horizontal line represents the axis of contraction (where winds are "smooshing" air together), and the vertical lines represent the axis of dilatation (where air is being "stretched").

In this case, looking at the mid-level mean wind forecasts that Wxman provided earlier, there appears to be a col, with TD7 located just ESE of the center. If it were located just a little farther south, it would be 'caught' in the zone of northerly flow south of the axis of contraction. Instead, as it looks now, it'll be north of the axis of contraction, so it'll be deflected northward.

EDIT: I edited the first graphic provided by wxman --> http://www.tornadocentral.com/now/col.png ... The axis of contraction is seen the bright green, dot-dash-dot segment; the axis of dilatation is represented by the dark green, diamond-shaped segment. The red dashed line represents an inverted trough, making the mid-level environment similar to the first example above. Streamlines become extremely useful for applications such as this.