ATL: GABRIELLE - Remnants - Discussion

[cycloneye]

00z Best Track.

AL, 97, 2013090400, , BEST, 0, 154N, 640W, 30, 1008, LO

[Gustywind]

SSD Numbers...

03/2345 UTC 15.4N 64.0W T1.5/1.5 97L

[TropicalAnalystwx13]

Definitely looks to be approaching tropical depression status right now. We'll see what happens with diurnal maximum. Could push it over the cliff. Also seems to have inherited a more poleward component...maybe just clip eastern Hispaniola or shoot the gap between it and Puerto Rico? We'll see.

[CronkPSU]

1.5 is an increase as well from this afternoon, right?

[TheStormExpert]

When is D-Max?

[Blown Away]

System looks on satellite to be moving more NW now...Seems the sharp recurve may be in the cards after passing near/over PR and/or Hispaniola...

[Gustywind]

1.5 is an increase as well from this afternoon, right?

Yeah, it's an increasing trend. Here is a recap of 97L since its first appareance

03/2345 UTC 15.4N 64.0W T1.5/1.5 97L
03/1745 UTC 14.4N 63.2W T1.0/1.0 97L
03/1145 UTC 14.5N 62.9W TOO WEAK 97L
03/0545 UTC 14.8N 61.4W T1.0/1.0 97L
02/2345 UTC 14.3N 60.3W TOO WEAK 97L
02/1745 UTC 14.0N 59.7W TOO WEAK 97L
02/1145 UTC 14.3N 59.4W TOO WEAK 97L
02/0545 UTC 14.2N 59.5W TOO WEAK 97L
01/2345 UTC 14.7N 61.7W TOO WEAK 97L
01/1745 UTC 14.0N 60.6W TOO WEAK 97L
01/1245 UTC 14.2N 60.8W TOO WEAK 97L
01/0545 UTC 13.5N 58.5W TOO WEAK 97L

[gatorcane]

System looks on radar to be moving more NW now...Seems the sharp recurve may be in the cards after passing near/over PR and/or Hispaniola...

Not necessarily. The Euro/UKMET also shows it going NW between the Dominican Republic and Puerto Rico for the first 48 hours or so then slowing down and bending more to the west between 48-72 hours with the Euro stalling it around Hispaniola or just north of for several days within weak steering current.

Not that I am saying it will following the Euro or UKMET considering all the other guidance suggests a sharp recurve, just pointing that out.

[TJRE]

Cimms -Mid-Level Shear 0000Z

Would one of the pro-mets be kind enough to embellish on this image for us???

High Pressure aloft? anti-cyclone support?

thank you TJ




Uploaded with ImageShack.us

http://tropic.ssec.wisc.edu/real-time/w ... oom=&time=

[floridasun78]

so if moving nw that mean will not affect bahamas some models show earlyer??? it go out to sea

[Hammy]

I'm wondering at this point if there's any chance that they'll investigate the more eastern system tomorrow as well if they fly out since they won't have too far of a trip to 97L--convection is on the increase and I see what appears to be westerly inflow.

[gatorcane]

System is moving WNW:

Information as of the most recent model cycle

At 0000 UTC, 04 September 2013, LOW INVEST (AL97) was located in the North Atlantic basin at 15.4°N and 64°W. The current intensity was 30 kt and the center was moving at 9 kt at a bearing of 290 degrees. The minimum central pressure was 1008 mb.

http://www.ral.ucar.edu/guidance/realtime/plots/northatlantic/2013/al972013/

[pgoss11]

I'm just wondering if the latest organization that's happening with 97L is what's given it that "poleward" motion look to it.

[HurriGuy]

Yeah I agree...the eastern blob looks pretty interesting.

[gatorcane]

I'm just wondering if the latest organization that's happening with 97L is what's given it that "poleward" motion look to it.

Looks can be deceiving because there is still some SSW shear impacting the system. That causes the convection to blow-off some to the north but the low-level center continues to track WNW.

[NDG]

As if the TW NE of 97L is getting absorbed by 97L and is helping in moistening the environment at least in the NE quadrant and eventually the northern quadrant which had very dry air during the last couple of days.

http://tropic.ssec.wisc.edu/real-time/m ... t72hrs.gif

[blp]

While 850mb vorticity has increased the 500mb vorticity has decreased a good deal in the last three hours.

http://tropic.ssec.wisc.edu/real-time/windmain.php?&basin=atlantic&sat=wg8&prod=vor2&zoom=&time=

[HurricaneTracker2031]

My forecast for Atlantic:

http://goo.gl/L0BpT9

[WYNweather]

When is D-Max?

Diurnal maximum and minimum. During the day it is diurnal minimum over water because, the surrounding air has less specific heat capacity than the sea,and thus warms faster, but cools down faster during the night. During the night time, the water is typically warmer than the surrounding air. Now the air near the surface which is in contact with the water warms by conduction, and then begin to rise. The during the day, the warming of the air which is above the water creates a quasi-capping inversion, inhibiting convection. Keep in mind that air rises from the surface to the higher levels, so when the air warmer than the sea during the day, it acts as a lid.

From weather underground.

[ozonepete]

Cimms -Mid-Level Shear 0000Z

Would one of the pro-mets be kind enough to embellish on this image for us???

High Pressure aloft? anti-cyclone support?

thank you TJ




Uploaded with ImageShack.us

http://tropic.ssec.wisc.edu/real-time/w ... oom=&time=

This shows mid-level shear, which is the shear between the lower and mid-levels of the atmosphere. Shear is the change in wind speed and direction with height, and this chart is mainly showing speed shear, or the amount of change in wind speed with height. The faster the shear, i.e. the faster the wind changes from the lower to higher levels of the atmosphere (or vice versa), the more negative the effect on tropical cyclones. Tropical cyclones require a low shear environment because their circular wind fields, even when very intense (such as a 100 knot cyclone) cannot handle outside interference to their "delicate" spinning balance. When shear increases it is like blowing on a spinning top - even relatively small interferences with the balancing act can tilt the upright position and cause major problems.
CIMSS always showed full shear from the lower levels all the way up to jet stream level. This year they've added mid shear, which shows shear from low to mid levels, which is a great added tool because if the full shear looks strong but mid shear doesn't look bad, we know that most of the shear is in the upper levels. That's what we see right now with this storm, and since this storm is just developing and thus doesn't reach very high up into the atmosphere (not higher than mid levels) we know it's not affected by the highest shear and thus shear is negligible for this to develop right now.
The chart also shows the direction of the shear - so we can see it is a clockwise flow right over the lower to mid-circ right now. That doesn't tell us anything about the upper flow so I would never use this chart to determine if there's a beneficial upper high over it. If you want to know that just use their upper level wind chart, ok?