ATL: GRACE - Renmants - Discussion

[Fego]

But with Danny and Erika is like a seasonal trend, although nothing is written on stone, so a strong shear outlook can change, more if is a long term outlook.

[LarryWx]

As several posts above have noted, shear levels all of the way to the Caribbean are pretty light and favorable. However, shear is forecasted by the 6Z GFS to increase between 45W and the Caribbean starting Wednesday as Grace gets toward that area. So, assuming that the 6Z GFS isn't in lala land, shear levels will not remain favorable once we get to Wed and beyond. If it is in lala land, that would be a different story. However, the higher shear is totally believable considering the strong El Niño. We'll see.

[cycloneye]

BULLETIN
TROPICAL STORM GRACE ADVISORY NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072015
1100 AM AST SUN SEP 06 2015

...GRACE CONTINUES WESTWARD OVER THE EASTERN TROPICAL ATLANTIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...12.9N 29.9W
ABOUT 450 MI...720 KM WSW OF THE CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES

[gatorcane]

As several posts above have noted, shear levels all of the way to the Caribbean are pretty light and favorable. However, shear is forecasted by the 6Z GFS to increase between 45W and the Caribbean starting Wednesday as Grace gets toward that area. So, assuming that the 6Z GFS isn't in lala land, shear levels will not remain favorable once we get to Wed and beyond. If it is in lala land, that would be a different story. However, the higher shear is totally believable considering the strong El Niño. We'll see.

Well we will see, but we do know forecasting shear in advance is difficult. It's one thing if the shear was already there right now, but it is not. The UKMET doesn't show this intense shear as it still shows a robust cyclone heading WNW by hour 132. I do see the GFS and ECMWF models increasing the shear by mid this week.

Also as we have seen with Fred, it may not be enough to kill off Grace and she could find more favorable conditions downstream, as Fred is now doing. As other posters have noted, going north of the Caribbean would be her best chance. We must remember had Erika done that as she was forecasted to, it could have been a much different situation.

[blp]

Grace is starting to look real good. Looks ready to take off.

[emeraldislenc]

Does anyone think it has an opportunity to reach a hurricane?

[LarryWx]

Does anyone think it has an opportunity to reach a hurricane?

In my mind it has a decent chance to become a H over the next 48 hours based on favorable shear.

[chaser1]

Does anyone think it has an opportunity to reach a hurricane?

In my mind it has a decent chance to become a H over the next 48 hours based on favorable shear.

Yep, totally agree. In fact, I will be a little surprised if Grace does not reach hurricane intensity in about 24 hours especially if a strong southerly outflow channel develops as the strong easterlies might suggest. I'd go so far as to guess that reaching Cat. 2 intensity might not be out of the question. Then, in light of Grace potentially becoming a deeper and larger cyclone (along with some added influence of Fred slightly weakening the ridge between the two systems... as considered by Crownweather above), this might impact a more northward component to Grace's near term motion, and then track a bit more westward after 36-48 hours. As for longer term prospects, i'm simply looking to see if the GFS continues to advertise the same strong vertical shear or if the shear (or timeline for its arrival) begins to change over the next few model runs.

[emeraldislenc]

Thanks for your opinion!

[LarryWx]

You're welcome.
As was noted in the models thread, the 12Z GFS has less shear forecasted than prior runs all of the way to 60W on Friday, when Grace is forecasted to get there. If its shear forecast happens to be accurate, that would mean it would have under 10 knots of shear if it remains south of 16N through that period. If it were to go up toward, say, 17N Wed-Fri instead of the currently forecasted 15-15.5N, then it would likely be hitting more unfavorable shear levels.

Chaser1, check out the 12Z GFS' lower shear near the forecasted center of Grace all of the way to 60w. My provider's shear maps have it under 10 knots at least til then near the center.

By the way, the 12Z GFS continues with the wet forecast for the VI/PR late week (1-2"), which would be helpful for the drought there.

[gatorcane]

12Z CMC model (not the greatest model) takes Grace north of the Caribbean and develops a hurricane out of this again with it eventually hitting the Bahamas and Florida. Thankfully, it is just the CMC model and is in the long-range - still there is potential in my opinion if Grace makes it north of the Caribbean in tact (as her predecessor Erika was supposed to do).

[ConvergenceZone]

12Z CMC model (not the greatest model) takes Grace north of the Caribbean and develops a hurricane out of this again with it eventually hitting the Bahamas and Florida. Thankfully, it is just the CMC model and is in the long-range - still there is potential in my opinion if Grace makes it north of the Caribbean in tact (as her predecessor Erika was supposed to do).

and as we all know, the stronger it gets before it gets to the islands, the more likely it is to be pulled a bit further north. Most of the models aren't factoring this in because they don't think it will go hurricane in that time period. Models are hit and miss when it comes to predicting strength. The next couple of days will be very interesting.

[Emmett_Brown]

Another storm in an el nino year, destined to be kept in check by shear if current NHC forecasts are correct. If this was a neutral or nina year, this would have probably been something to watch out for. Always prepare though, you never know. My guess is this will be an open wave by the time it makes it to the Caribbean.

[LarryWx]

With Grace having become a TS E of 50W in the MDR, that makes a whopping 4 this season. Looking back at the prior 17 developing strong+ El Nino years, this breaks the old record set in 1899, when there were 3. 1987 had 2. The other 15 had only either 1 or 0! Keep in mind that this includes 6 seasons during the satellite era. So, the record high during the satellite era's 6 developing strong+ El Nino seasons was only 2 til this season's 4! So, 2015 is clearly on its own with regard to storms that formed E of 50W. Furthermore, there's no telling that we're done at 4 being that it is only 9/6.

[YoshiMike]

Nice input. Definitely something to think about.

[blp]

i was looking at that. I think we could get at least two more. Very interesting season we have this year. Can you imagine if we did not have the shear in the Carribean.

[TheStormExpert]

Another interesting thing to note is the fact that 4 of the 7 named storms this season have formed in the MDR and East of 50W! Both hurricanes formed and were respectively hurricanes only in the MDR as well.

[TheStormExpert]

:uarrow: i was looking at that. I think we could get at least two more. Very interesting season we have this year. Can you imagine if we did not have the shear in the Carribean.

IMHO if that storm killing shear did not exist Florida very well could've had it's first hurricane hit since 2005 already!

[YoshiMike]

Agreed

[chaser1]

As was noted in the models thread, the 12Z GFS has less shear forecasted than prior runs all of the way to 60W on Friday, when Grace is forecasted to get there. If its shear forecast happens to be accurate, that would mean it would have under 10 knots of shear if it remains south of 16N through that period. If it were to go up toward, say, 17N Wed-Fri instead of the currently forecasted 15-15.5N, then it would likely be hitting more unfavorable shear levels.

Chaser1, check out the 12Z GFS' lower shear near the forecasted center of Grace all of the way to 60w. My provider's shear maps have it under 10 knots at least til then near the center.

Hey Larry you're right. Seems like the prior GFS runs wanted to overstate downstream (48hr.-96hr) upper level shear through the evolution of newly divergent "jet" that was to develop off the strong northerly flow into a developing upper anticyclone over the Central Caribbean. I think a lot is also dependent on if/how much "beefier" Grace becomes. Right now, she's looking like she hasn't eaten in a day lol. Will be interesting to see if she not only starts popping some impressive convection again later this afternoon, but more importantly whether she's got the capacity to move beyond a diurnal process and begin to better maintain her convection.

Interestingly, the 12Z model seems to move the upper high to the west a bit quicker, but more importantly seems to lessen the depth of any trough in the upper high's wake, thus no longer indicating a strong southwesterly upper level shear as before. What seems to still remain is a shear zone of about 20 knots that ride west to east along (or just below) 20N, however given the general long-wave positioning of the W. Atlantic upper level ridging... I have to question whether a well developed tropical cyclone might deflect that flow and furthermore have to even question what would seem to be erroneous 200mb SW wind-barbs depicted in the S.E. Caribbean (at 78 hours) given the lack of an apparent TUTT and strength of the upper high to its west. Of course, these are musings over one model run. Just as Gatorcane mentioned a short while ago about CMC eventually bringing Grace up towards the Bahamas , I'm beginning to feel that nearly all the models have become a bit more crazy this past year. Definitely need a bit more symmetry and look for trends in future runs.