ATL: GRACE - Renmants - Discussion

[WPBWeather]

If this season wasn't an El Nino year then this storm could of been potentially a big threat down the road.

Don't count anything out yet. Some terrible storms come in El Nino years.

[BobHarlem]

If this season wasn't an El Nino year then this storm could of been potentially a big threat down the road.

Don't count anything out yet. Some terrible storms come in El Nino years.

True, but with Danny/Erika as examples so far, and no reason to believe it will be any different this go around with Grace, it's hard to do so other than watching it probably fall apart later on (just looking at the NHC forecast).

[emeraldislenc]

You are right never let your guard down if it moves north of the islands it could have a dufferent outcome!

[Yellow Evan]

If this season wasn't an El Nino year then this storm could of been potentially a big threat down the road.

Don't count anything out yet. Some terrible storms come in El Nino years.

True, but with Danny/Erika as examples so far, and no reason to believe it will be any different this go around with Grace, it's hard to do so other than watching it probably fall apart later on.

All storms eventually die.

This season could IMO be better but it could be worse. So far it's exceeded expectations.

[cycloneye]

For me,2015 season has been above what I expected on MDR in terms of ACE.

[gatorcane]

Convection is back on the increase near the llc (sw side)

[gatorcane]

It is interesting to note the new GFS run brings Grace down to 991MB by hour 60. That is much stronger than the previous GFS run. GFS does not show weakening until around day 4 now pushing out the timeframe when that commences. I wonder if the NHC will consider this in the discussion / intensity forecast for the upcoming update or if they will wait for the overnight model runs to see if they come in more intense.

[blp]

For me,2015 season has been above what I expected on MDR in terms of ACE.

Agree, everything from here on out is gravy. Take a look at this tweet from Dr. Klotzbach. Puts your post in perspective.


45m45 minutes ago
Philip Klotzbach ‏@philklotzbach
Grace has formed in the tropical Atlantic. The 1981-2010 average for 7th named storm formation is 9/13.

[cycloneye]

TROPICAL STORM GRACE DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072015
1100 PM AST SAT SEP 05 2015

Most of the deep convection associated with Grace is located west
and southwest of the estimated center position, consistent with
light-to-moderate easterly shear analyzed over the cyclone by
UW-CIMSS and the SHIPS model. The initial intensity remains 35 kt
based on the latest Dvorak classifications from TAFB and SAB. Grace
will be moving over warm waters and in a low shear environment for
the next 24 to 36 hours, which should support some strengthening.
After that time, the shear becomes westerly and increases with the
cyclone moving over slightly cooler waters. As a result, much of the
intensity guidance suggests that Grace will weaken later in the
period, with dissipation also possible. The new NHC intensity
forecast is similar to the previous one and is close to the latest
IVCN intensity consensus.

The initial motion estimate is 280/12. Grace should continue moving
generally westward to west-northwestward to the south of a
subtropical ridge for the next several days. The track model
guidance is in good agreement on this scenario, although there is
some variability in forward speed. The new NHC track forecast is
an update of the previous one and lies a little south of the
consensus given that Grace is forecast to be weaker by the end
of the period. This track is close to the latest predictions from
the GFS model and the FSU Superensemble.

FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 12.8N 27.5W 35 KT 40 MPH
12H 06/1200Z 13.0N 29.5W 40 KT 45 MPH
24H 07/0000Z 13.3N 32.3W 45 KT 50 MPH
36H 07/1200Z 13.6N 35.1W 50 KT 60 MPH
48H 08/0000Z 14.1N 38.0W 45 KT 50 MPH
72H 09/0000Z 14.8N 44.2W 45 KT 50 MPH
96H 10/0000Z 15.3N 49.5W 40 KT 45 MPH
120H 11/0000Z 16.0N 54.5W 35 KT 40 MPH

$$
Forecaster Brennan

[Hammy]

I just checked the satellite for the first time in about four hours or so, and how things have changed.


100z

445z

[Hammy]

:uarrow: I'm inclined to think there is 2 vor'ts with no dominate one atm whats your thinking hammy.

cropped for locational consistency:


Earlier pass, at 111z appears that there may have indeed been both a northern and southern vortex, or at least some displacement between low and mid-level. Grace appears to be rapidly organizing at the surface though, as the 331z pass shows what may be a mid-level eye type feature forming, about midway between the two earlier vortices.


Latest pass shows it as well (unfortunately seems to be lower resolution)

Very deep westerly flow at low levels is there as well, with a nice inflow band visible there. Especially given how the season was expected to go, Grace seems to be consolidating quickly tonight. It would be nice to get an ASCAT pass to get a better idea of the intensity.

[Gustywind]

000
WTNT32 KNHC 060839
TCPAT2

BULLETIN
TROPICAL STORM GRACE ADVISORY NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072015
500 AM AST SUN SEP 06 2015

...GRACE STRENGTHENING OVER THE EASTERN ATLANTIC...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...12.4N 28.5W
ABOUT 390 MI...630 KM SW OF THE CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES

[Hammy]

One last pass before I'm overcome with drowsiness shows what I'll now call a formative eye, though convection seems to be collapsing in recent hours.

[gatorcane]

Latest floater loop, nice spin and movement appears to be a little north of due west as it is gaining a little latitude:

[ronjon]

Becoming much better organized. Might have a window of another 24 hrs to strengthen.

[abajan]

Despite everything that's going against its development (shear, dry air etc.) I feel it's going to become a hurricane sometime within the next couple of days, if only briefly. I have nothing to support this. It's just a hunch. I actually felt so from the time it left Africa but time will tell.

This post is NOT an official forecast and should not be used as such. It is just my opinion and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[gatorcane]

Grace now showing up in the wide Atlantic satellite, far right:

[gatorcane]

Right now at least I don't see any cyclone-killing shear in the path of Grace, in fact the upper-level winds look favorable all the way until the Leewards. Of course these shear maps do change and are not static:

[Fego]

I agree , but then I got kind of confused when I saw this 06z GFS 200mb-800mb wind shear image at 126 hours. Am I missing something?

[crownweather]

Two thoughts gatorcane and others - I'm wondering if Fred may leave a weakness in the ridge to pull Grace a little further north than the guidance suggests. Should this happen, it could potentially pull Grace far enough north to either brush the NE Caribbean or miss it altogether and head towards the Bahamas (i.e. Canadian model & yesterday's GFS model). It's a long shot, I know, but it is something that I noticed in doing my analysis this morning.

Another thought, like you mentioned gatorcane, is that I don't see the tropical cyclone shear that the guidance is forecasting for later this week. Yes, there is currently 30 knots of shear in the NE Caribbean and also over the central/western Caribbean, but elsewhere, at maximum it is 15-20 knots. It has made me take a harder look at whether Grace will in fact meet such a quick demise like the models are forecasting.