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General Discussion >> 2017 Forecast Lounge

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cieldumortModerator
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HUR. GERT Lounge
      #97785 - Thu Aug 03 2017 02:16 AM



A vigorous and fairly sizable wave rolling off the westernmost tip of Africa this morning has the interest of many models. Conditions for development this week and into next are much better than encountered by recent waves which attempted to get going within the monsoon trof in the central-east Tropical Atlantic (see Lounge).

As of the August 3, 2017 2AM TWO, NHC has assigned 50-50 odds that this wave becomes a tropical cyclone within 5 days. It is worth noting that forecast environmental conditions suggest that this feature could become a long-track hurricane. Movement is likely to be west or west-northwest at 10 to 15 mph for the next several days.

Invest 99L has become TD8 and the title has been updated. - Ciel


Edited by cieldumort (Tue Aug 15 2017 06:56 PM)


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MikeCAdministrator
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Re: Significant E Atl Wave (99L) [Re: cieldumort]
      #97787 - Thu Aug 03 2017 07:41 AM

Long range speculation includes watching the global (and other) forecast models to watch for trends, when a system is still an invest and not fully developed things can (and do) change wildly from run to run, but they tend to vary less as time goes on. These models are helpful in that they give a general path to look for, and we look for consensus and stability between runs to gauge confidence in what they do. many times the position of the system in the model isn't as important as the conditions (Ridges/troughs/lows/upper level lows/dry conditions) around it.

That said, here's the first model set for 99L:

0z Euro: Not as strong as it was on the prior run, but it has it crossing the leewards as a Tropical Storm Tuesday night, then falling apart int the Caribbean afterwars (another system near the Yucatan starts going in the Bay of Campeche).

6z GFS: Develops a hurricane around 40W in the Central Atlantic Monday morning, keeps it north of the Caribbean islands, and bends it back west (north of the Bahamas), and has a major hurricane landfalling in coastal Georgia near Brunswick/St..Simons on Thursday August 17th (2 weeks from today). The 0z run prior to this had the same result. After landfall the 6z GFS turns it northward inland over North Georgia then eastern Tennessee (Knoxville) into Kentucky and Indiana weakening rapidly. (with a ton of rain).

The fact the models want to push this so far west implies the high will be strong around that time, which would increase the odds for some sort of impact on the land US down the road, if it doesn't stay south and go through the Caribbean like the current Euro Shows. So some sort of impact is likely, to what degree and where (islands vs US) is still up in the air. If the trend moves east during the next few runs, out to sea becomes more likely.

Way too early to say which is going to be more correct, nothing has developed yet, and the first runs are typically very wrong.



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MikeCAdministrator
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Re: Significant E Atl Wave (99L) [Re: cieldumort]
      #97790 - Thu Aug 03 2017 01:19 PM

12Z GFS run seems a bit off on initialziation (phantom wave from the real wave?) But is east and out to sea this time, with no direct landfall.

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M.A.
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Re: Significant E Atl Wave (99L) [Re: MikeC]
      #97792 - Thu Aug 03 2017 04:01 PM

So far it looks to be a fish spinner. Bermuda could see some of this one. The CV season is upon us.

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MikeCAdministrator
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Re: Significant E Atl Wave (99L) [Re: MikeC]
      #97793 - Thu Aug 03 2017 05:25 PM

12Z Euro is still into the Caribbean, so I wouldn't jump to that conclusion this far out, I pointed out the GFS had a bad init latching onto a phantom area rather than the actual low, (too far west), I think the answer is somewhere in the middle.

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MikeCAdministrator
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Re: Significant E Atl Wave (99L) [Re: MikeC]
      #97794 - Thu Aug 03 2017 07:47 PM

18Z GFS is back further west with a much closer approach to the Bahamas on August 13th, but not over, and then makes landfall as a major hurricane on the NC outer Banks near Morehead City on August 15, heads over Hampton Roads/Norfolk and back out into the Atlantic then races over eastern Long Island and over Boston on august 16th. Slightly better init than the earlier run. GFS does not really develop invest 90L (the other one being tracked) in the bay of Campeche at all.


Esemble spread is biased toward the east.

Still a lot of uncertainty there, but 99L will likely be a long lived tropical system that can be watched over the next week or two. The leewards still need to watch it also, the GFS seems to be overdoing development right now.





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MikeCAdministrator
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Re: Invest 99L Lounge [Re: cieldumort]
      #97796 - Fri Aug 04 2017 12:08 AM

0z GFS run rolling in so far it looks like it will miss the Caribbean to the north on this run, however Euro will still likely take it into the Caribbean. Closest approach for the Caribbean is Thursday night into Friday. At this far into the run (+186 hour) it's slightly south of the prior 18Z run. Ridging to the north is fairly strong also.

After this, it gets very close to the Turks and Caicos islands in the Bahamas, enough to be a problem there. Into the central Bahamas late August 12th into the 13th. Bermuda high is strong, major hurricane over Nassau on the 13th.

Late evening on the 13th, its very close to Florida, very close or just over Cape Canaveral (925mb major hurricane) but stays just offshore (very similar to Matthew), eventually landfalls near Savannah/Hilton Head on Aug 15th, a bit weaker, then rides inland through North Carolina.

earlier runs of the CMC misses the islands and takes it out to sea, the UKMET rides it through the northern Caribbean islands (weak)

The newer 0z run of the CMC is weaker, but much further west.

Splitting the difference takes it very close to the northern Caribbean islands, maybe skimming Hispaniola after missing Puerto Rico barely to the north.

HMON/HWRF develop it into a hurricane in about 5 days.

In short still too soon to tell impacts, about a 50/50 split for Caribbean impact, and much less for US/Bahamas impact, but more than earlier. A slight shift to the west. The most alarming thing about the GFS is the 600dm ridge that holds for several days, which would likely force the storm west and raises the chances of land impacts a great deal (taken in isolation, if the trend holds, even more so)

99L needs to be watched VERY closely over the next week and a half.




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MikeCAdministrator
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Re: Invest 99L Lounge [Re: MikeC]
      #97797 - Fri Aug 04 2017 06:15 AM

To balance out the 0z GFS run, the 0z Euro run weakens it a bit before crossing over the Leeward islands on Wednesday then rapidly weakens it in the eastern Caribbean and it gets torn up near Hispaniola and brings some rain to Jamaica as a weak low, Friday August 11th. Interesting to note that the The Euro is faster with the system forward movement than the GFS.

The GFS shifted back a bit east, missing the Bahamas and Florida this time, gets very close to Cape Hatteras on Aug 15th and close to Cape Cod on the 16th, but it stays east and recurves it out.

The Euro halso has a strong rdige, but it keeps the system in the Caribbean. So the 50/50 shot for going north or through the islands is still there.

System is important to watch, but way too early to say where it winds up.


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M.A.
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Re: Invest 99L Lounge [Re: MikeC]
      #97800 - Fri Aug 04 2017 07:19 AM

This is certainly grabbing my attention. Looks to be a very interesting week to come. Still hoping for a fish spinner.

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MikeCAdministrator
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Re: Invest 99L Lounge [Re: M.A.]
      #97801 - Fri Aug 04 2017 09:02 AM

the GFS seems to be really overdoing intensity on 99L, so I suspect it's a bit off. It may be a close call for the Leeward Islands. Particularly since dry air will stall any development today or tomorrow.

On the normal model plots, I'd think the TVCN is most likely (This doesn't mean much, however)


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MikeCAdministrator
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Re: Invest 99L Lounge [Re: MikeC]
      #97802 - Fri Aug 04 2017 11:34 AM

!2Z GFS starting to roll in, starts off weaker than the last run, but recovers at 24 hours. (Yesterday's 12Z run already had it as a Tropical storm right now, and obviously that didn't happen)

By 48 hours, the position is about the same as the 6z run, but its a bit weaker. TD/tS vs hurricane.

by 96 hours it moves faster and a bit further south of the earlier run, this appears to be closer to the Euro run, although it is a strong Tropical Storm at this point. This run seems more realistic toward actual conditions than the prior run.

At 120 hours out it is much further southwest than the earlier run, and nearing the northern leeward islands, tropical storm strength.

Near/over St. Johns and Barbuda in the Leewards on Thursday morning as a Tropical Storm then moves over/near St. Kitts, toward the Virgin Islands.

Tropical Storm landfall on Puerto Rico Thursday night, then moves toward Hispaniola, by friday night it's over Haiti and getting torn apart. By Saturday morning the remains are over Guantanamo in Cuba.

By Monday, August 14th it emerges west of Cuba into the Gulf and gets a little stronger, maybe a TS again, then heads toward southeastern Louisiana with a TS landfall late afternoon on the 15th.


This is closer to the Euro run and much weaker (never gains hurricane strength) and stays weak.


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MikeCAdministrator
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Re: Invest 99L Lounge [Re: MikeC]
      #97803 - Fri Aug 04 2017 02:42 PM

12Z Euro does not develop 99L, moves it into the Caribbean.

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MikeCAdministrator
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Re: Invest 99L Lounge [Re: MikeC]
      #97804 - Fri Aug 04 2017 09:01 PM

18Z GFS back to something.

Strenghtens to a TS around Monday/Tuesday in the Atlanta, weakens a bit as it gets closer to the Leewards, goes over Barbuda Late Wednesday night into Thursday morning, barely misses Puerto Rico to the north on Friday, then stays just north of Hispaniola, Stays north of Cuba, Goes over the middle Florida Keys on Sunday August 13th as a major hurricane, ,rides just offshore of the west coast of Florida as a major hurricane. Landfall near Panama City, FL on August 14th, as a major hurricane, then up through Alabama/Georgia and Eastern Tennessee,


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MikeCAdministrator
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Re: Invest 99L Lounge [Re: MikeC]
      #97805 - Sat Aug 05 2017 08:26 AM

Overnight model runs show a much weaker system, GFS an Euro included, the Euro does not develop 99L at all, while the GFS does develop a tropical storm that crosses the leewards Wednesday Morning then weakens and eventually dissipates over Hispaniola. The NHC is slowly dropping chances for development based on the Euro's persistence in not developing the system.

The storm's forward motion has been faster than earlier GFS model runs showed.


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MikeCAdministrator
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Re: Invest 99L Lounge [Re: MikeC]
      #97806 - Sat Aug 05 2017 12:02 PM

12Z operational GFS run continue to keep the system weak, and moves it into the northern Leeward islands a depression or wave Wednesday night into Thursday. Weakens it into a wave and clips the eastern side of Puerto Rico on Thursday. The main vortex stays north of Hispaniola on this run, but it remains weak (just a wave/TD) on Friday then loses it entirely.




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MikeCAdministrator
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Re: Invest 99L Lounge [Re: MikeC]
      #97808 - Sat Aug 05 2017 02:21 PM

12Z Euro is a bit stronger for this system than prior runs, shows potential for development for 99L Tue-Wed where before it did not. This is very similar to the 12Z GFS run this time, with the system north of Puerto Rico on Friday, but as a wave or weak depression. Just a bit slower.


The elongated nature of this system is making it difficult for anything to get going, but general conditions aren't bad for it, it has two competing areas for a center to develop, and neither is winning out right now.


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MikeCAdministrator
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Re: Invest 99L Lounge [Re: MikeC]
      #97810 - Sun Aug 06 2017 08:10 AM

This mornings runs have brought concern back to 99L.

The 0z Euro now moves the system north of the Caribbean, and starts to develop it a week from today (aug 13th) east of the Bahamas, at the end of the run (Aug 16) there is a hurricane sitting off south Carolina, with it still moving toward land.

The 6Z GFS is similar but it clips the northern Bahamas on August 13th, as a weaker system, then bends it back north for a near landfall between Charleston and Myrtle Beach on Aug 15th and then rides along the coastline through the outer banks.

Still too far to say much of anything about this system other than continue to watch it.


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IsoFlame
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Re: Invest 99L Lounge [Re: MikeC]
      #97815 - Mon Aug 07 2017 10:23 AM

With the 25th anniversary of Hurricane Andrew approaching, initially weak, long-track 99L will be monitored for any potential to rapidly develop ITVO the Bahamas late weekend/early next week- especially if the ridge strengthens to the north of the system about the same time.

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JMII
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Re: Invest 99L Lounge [Re: IsoFlame]
      #97817 - Mon Aug 07 2017 11:00 AM

Any Cape Verde storm that pops up normally catches and keeps my attention. With so much warm water to traverse the potential for a strong system is higher then normal. The models have clustered a bit further north and currently 99L's development is less favorable so hopefully those trends continue.

--------------------
South FL Native... experienced:
David ('79) - Floyd ('87) - Andrew ('92) - Georges ('98) - Irene ('99) - Frances & Jeanne ('04) - Katrina & Wilma ('05) - Matthew ('16)


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MikeCAdministrator
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Re: Invest 99L Lounge [Re: JMII]
      #97818 - Mon Aug 07 2017 11:14 AM

Not much to update with 99L, none of the major models do anything with it anymore, but it still is a good idea to Monitor, particularly when it gets north of the Caribbean.

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