Tropical Depression Dorian

[Ed Lizard]

I think with the new system, the GFS is a wildcard,  And hitting Hispaniola perfectly from the East takes a near straight Westward track, with barely a hint of motion North of due Westward.  With Euro never seeing this system, really, and BAM, HWRF and GFDL models initialized off the GFS guidance, I think model guidance will be extra useless.

 

They should have waited until after Dorian, switched super computers, and then debugged, IMHO.

 

Or not, 12Z Euro ensembles are further South, although I expect because many weakened Dorian to a wave...

 

Dorian is obviously sheared, but I *think* it is keeping convection near the LLC.

 

 

[Superstorm93]

Dorian is looking pretty sickly 

 

At this point, I wouldn't be surprised if it didn't degenerate into a wave at some point over the next 120 hours. Even if it doesn't degenerate, it'll still have to contend with the Greater Antilles. So all in all, it's future is bleak to say the least. 

[thewxmann]

Hey, at least the latest Euro keeps Dorian as an intact entity to SE FL.

[Floydbuster]

The NHC track shows a bend directly towards Southeast Bahamas and Southeast Florida in 120 hrs. Of course, if this were in an ideal environment, it would be a significant threat. If Dorian makes it there, odds favor it being weak.

[AutoPenalti]

I still have hope that this system will survive

[dtk]

They should have waited until after Dorian, switched super computers, and then debugged, IMHO.

Ha.  The computer switch was a long time in the making.  Many developers spent countless hours working on codes, transitioning to the new hardware/software, testing, debugging, etc.  There was a ton of evaluation done over the past several months, of the WCOSS-run codes.  The GFS on WCOSS is statistically indistinguishable from the CCS version (in terms of nearly all verification metrics).

 

NCO moved the go-live date up to yesterday as things had been stable for some time (there was a hardware/disk issued that led to the original postponement), out of an abundance of caution.  If Dorian survives and we have a TC in the Caribbean/threatening U.S. interests, we would have entered a CWD.  If in a CWD, we would be unallowed to make the switch (costing the government, and taxpayers, a ton of money to keep the old CCS up and running).

 

The only "bug" that was found (at least thus far) was related to a minor land surface issue with the NAM.  This was simply a code/version control mistake.  The fix is already identified and will be going in soon.

 

Given the aggressive timeline and the amount of work that went into this machine transition, it is nothing short of a minor miracle we were able to go live when we did without any major hiccups.

[Srain]

Ha.  The computer switch was a long time in the making.  Many developers spent countless hours working on codes, transitioning to the new hardware/software, testing, debugging, etc.  There was a ton of evaluation done over the past several months, of the WCOSS-run codes.  The GFS on WCOSS is statistically indistinguishable from the CCS version (in terms of nearly all verification metrics).

 

NCO moved the go-live date up to yesterday as things had been stable for some time (there was a hardware/disk issued that led to the original postponement), out of an abundance of caution.  If Dorian survives and we have a TC in the Caribbean/threatening U.S. interests, we would have entered a CWD.  If in a CWD, we would be unallowed to make the switch (costing the government, and taxpayers, a ton of money to keep the old CCS up and running).

 

The only "bug" that was found (at least thus far) was related to a minor land surface issue with the NAM.  This was simply a code/version control mistake.  The fix is already identified and will be going in soon.

 

Given the aggressive timeline and the amount of work that went into this machine transition, it is nothing short of a minor miracle we were able to go live when we did without any major hiccups.

 Thanks for the factual update, dtk. For all the poo pooing that some like to toss around about NOAA and the operational aspects of the NCEP, we have a darn good system and many dedicated folks that work very long hours and go un noticed to the average citizen. We still have the best weather forecasting folks in the world as far as I am concerned and the efforts to provide a reasonable operational computer generated forecasting tool have not been lost by those who tend to be a bit more weather wise, than not.

[Ed Lizard]

Maybe something did just change with the actual expected track of Dorian.  I just saw the GFS suddenly swing Southward, and found it odd.

 

 

 

Latest GFDL and HWRF show Dorian weakening even before the Greater Antilles, and suicide by Hispaniola seems a distinct possibility for an already not particularly strong system.  The GEFS means shows that while there is a spray in the tracks, the Northernmost tracks are the ones likely to survive beyond 5 days and they'd be recurving.

 

 

Natural optimistic nature, still holding out hope for Florida, although FIM, which seems to have an optimistic track for possible South Florida excitement, never gets Dorian much over 50 knots even before it starts running just North of the Greater Antilles.

 

[Ed Lizard]

Hot link, not attachment

 

Two things, while the center appears to be on the Northwest side of the convection, it doesn't seem exposed.

 

That said, although it could be because the center is mostly obscured, I'm not sure I can see Earth relative West winds South of Dorian.

 

[IsentropicLift]

Hot link, not attachment

 

Two things, while the center appears to be on the Northwest side of the convection, it doesn't seem exposed.

 

That said, although it could be because the center is mostly obscured, I'm not sure I can see Earth relative West winds South of Dorian.

 

I was going to post earlier that to me it looks like an open wave, but that could just be because the two centers are so disjointed.

 

Why can't we get a non struggling storm anymore? Seems like even when 99% of the conditions are favorable the 1% seems to win out. Other than the fact that the lower level flow was to fast, all the other pieces seemed to fall into place after it jumped the sub 26C SST hurdle two days ago.

[Ground Scouring]

Dorian is looking pretty sickly 

 

At this point, I wouldn't be surprised if it didn't degenerate into a wave at some point over the next 120 hours. Even if it doesn't degenerate, it'll still have to contend with the Greater Antilles. So all in all, it's future is bleak to say the least. 

Less than 24 hours ago some people thought (based mainly upon their own interpretation of the less-reliable HWRF and GFDL, plus how good Dorian looked for a time) it would be quite a robust system. I'm glad that I knew that this would degenerate and head into Hispaniola. The small size of this system was its own enemy.

[IsentropicLift]

Less than 24 hours ago some people thought it would be quite a robust system. I'm glad that I knew that this would degenerate and head into Hispaniola. The small size of this system was its own enemy.

I'm a fan of smaller storms. They take less time to complete ERC's and they tend to strengthen more rapidly.

[Ground Scouring]

I'm a fan of smaller storms. They take less time to complete ERC's and they tend to strengthen more rapidly.

Small storms are never preferable in an environment with substantial stable air and/or easterly wind surges.

[bluewave]

This summer is at least is starting out like the last two in that we will have 4 weak storms by the end of July.

[Weathergun]

I was going to post earlier that to me it looks like an open wave, but that could just be because the two centers are so disjointed.

 

Why can't we get a non struggling storm anymore? Seems like even when 99% of the conditions are favorable the 1% seems to win out. Other than the fact that the lower level flow was to fast, all the other pieces seemed to fall into place after it jumped the sub 26C SST hurdle two days ago.

 

More shear and dry air, were always factors, after moving over warmer SSTs.

 

The models often too quick with weakening/lifting out ULLs. I suspect conditions will remain unfavorable for the next 3-4 days.

[phil882]

I was going to post earlier that to me it looks like an open wave, but that could just be because the two centers are so disjointed.

 

Why can't we get a non struggling storm anymore? Seems like even when 99% of the conditions are favorable the 1% seems to win out. Other than the fact that the lower level flow was to fast, all the other pieces seemed to fall into place after it jumped the sub 26C SST hurdle two days ago.

 

You can't forget that we are still only in the last week of July... in fact having two Cape Verde TCs in July is nearly unheard of. They may have not be impressive systems, but all four TCs that have occurred in June and July had mainly tropical origins. You can't say that about 

 

 

This summer is at least is starting out like the last two in that we will have 4 weak storms by the end of July.

 

Its worth noting that the 2011-2013 period, we have had a total of 12 named storms in the May-July period. Meanwhile the climatological average for that time period should be between 3-5. Its been very unusual how much early season activity we have had the last few years. 

[Ed Lizard]

Silver lining optimism- the 6Z FIM 9 opens Dorian to a wave before it reaches the Greater Antilles.  Silver lining, corpse of Dorian passes through Cuba, per 15km FIM, there is still a distinct wave, with an 850 mb RH max.

 

Not so silver, 850 mb flow away from the decrepit picture of Dorian (Gray) suggests Westward or West-Northwest motion, or towards South Texas, 500 mb flow is West to West-Southwest, towards the Mexican coast, or a suggestion of some mid level shear.  Not horrible, but not perfect.  Deep shear is tricky, Dorian's corpse North of a 250 mb cyclone, or Easterly flow.  Not the preferred anticyclone aloft, but not horrible from a deep shear perspective.

 

Weenie wishcasting, while OHC remains almost negative where it counts, offshore Galveston, it seems decent enough to within fairly close to the Deep South Texas and Mexican coasts.  Weenie and not ashamed wishcasting, while it seems increasingly likely Dorian will die with or without Hispaniola's help, I am 3/64th glass half full optimistic on regeneration into a tropical cyclone before reaching Tamaulipas or extreme Deep South Texas, and 1/32nd optimistic it would be at least a high end tropical storm.

 

Further silver lining of a different nature, while 6Z GEFS individual tracks are a spray from the Gulf through a recurve, mean GEFS MSLP still suggests the perturbations that do keep a cyclone will come close (but probably fish) to the Southeast US.  And a TC hit on the SE US or Mexico, even if not a tight core hurricane, my natural rose colored glasses outlook would I allow me to appreciate either,

 

[gulfcane]

[icebreaker5221]

You can't forget that we are still only in the last week of July... in fact having two Cape Verde TCs in July is nearly unheard of. They may have not be impressive systems, but all four TCs that have occurred in June and July had mainly tropical origins.

 

Yeah, glad someone brought this up.  I'd much rather what we've had the last 3 years than much of the 1980s: 80, 83, 84, 87, and 88 all produced zero named storms before Aug 1.  At least a TS is something to talk about. 

[Ground Scouring]

You can't forget that we are still only in the last week of July... in fact having two Cape Verde TCs in July is nearly unheard of. They may have not be impressive systems, but all four TCs that have occurred in June and July had mainly tropical origins. You can't say that about the past few seasons' early storms.

That alone tells me (and any thinking person) that conditions in the deep tropics this year are far more favorable than they were in 2011 and 2012, with a greater amount of instability, a favorable IOD / MJO configuration, and generally a favorable global base-atmospheric state. The consistently-sterling quality of the waves coming off Africa indicates a more robust ITCZ, and SAL is much lower this July than in recent seasons--and is even lower than what you would normally expect in July, when the Saharan heat ridge / SAL reaches its greatest extent. And to be honest, from a chasing standpoint, I would be much more satisfied with a slow-starting season like 1958, 1961, 1996, or 2004--along with a bunch of others--that ended up as extremely active in August-October. They were also top-quality seasons with a high hurricane-to-total-NS ratio and many major storms. In 1961, in fact, the second named storm did not form until September, and then four major hurricanes formed in an incredibly active two-week period. Don't forget 2004's August-September onslaught: nothing formed until Alex on 31 July, and then four hurricanes hit FL in a little more than two weeks. And by the way, all these years, like this year, featured none of the subtropical crap we have come to expect during a dull peak season. These were explosive years with a large number of landfalls. Slow start? I don't give a whit about that. That's not what counts here.

[Ground Scouring]

I'm not sure why Levi is so aggressive with his forecast. His track by days four and five is too far N of the NHC's and is very unlikely to verify in either strength or path. A track N of Hispaniola is predicated upon a stronger, more well-stacked Dorian than is currently the case. I have a feeling that he is bucking the trend and forecasting a path N of the islands, and an intensity higher than that of the NHC by day five, mainly to earn more followers. His last forecast for Chantal busted horribly by deviating from the NHC and being too aggressive. If that happens again, I would conclude that he is too self-possessed with his following to be an objective forecaster.

http://www.tropicaltidbits.com/blog/2013/07/26/dorian-struggling-more-today-long-term-future-still-uncertain/

 

(I am posting this as a lesson to anyone--no one in particular, however--who may feel tempted to post nonsense that plays up a system more than what, objectively, it deserves.)

[IsentropicLift]

The 12z GFS degenerates Dorian into an open wave within the next 48-72 hours northeast of the islands

[bluewave]

You can't forget that we are still only in the last week of July... in fact having two Cape Verde TCs in July is nearly unheard of. They may have not be impressive systems, but all four TCs that have occurred in June and July had mainly tropical origins. You can't say that about 

 

 

 

Its worth noting that the 2011-2013 period, we have had a total of 12 named storms in the May-July period. Meanwhile the climatological average for that time period should be between 3-5. Its been very unusual how much early season activity we have had the last few years. 

 

The strong West African Monsoon helped for the early far east Atlantic development. But the drier and more stable

conditions to the west limited the strengthening  potential. Bertha in July 08 had much more favorable conditions

to develop into a major. 

 

 

 

July 2013

 

 

July 2008

 

[Ed Lizard]

Yeah, glad someone brought this up.  I'd much rather what we've had the last 3 years than much of the 1980s: 80, 83, 84, 87, and 88 all produced zero named storms before Aug 1.  At least a TS is something to talk about. 

 

 

83, 88 and the unmentioned but 'slow' 1992 may not have had action before August 1st, but all had serious red meat storms hitting or barely missing the United States.  Quality trumped quantity. 

 

 

Anyway, silver lining again, new GFS sort of like 6Z FIM, could a remnant wave of Dorian drift Westward and bring rain to Texas?  We really haven't had a real Easterly wave type rain event yet this year.  Not sure looking at the GFS rain with Dorian's corpse would get here, but something to hope for.

 

 

Just looked at vis loops again with lat/long turned on for reference, and I see no signs of West winds in low clouds South of Dorian already,  48 hours to degeneration back to an open wave might be generous.

[TropicalAnalystwx13]

Call me crazy, but I'm not completely sure Dorian is going to degenerate over the next few days. There's a lot of dry air around, for sure, but the system is entering ever-increasing sea surface temperatures and seems to be responding accordingly. Over the past few hours, constant bursts of convection have been forming over the low-level center; its still closed, and barely, but this should help it. Chantal may have been special, but if it survived, I don't see any reason why Dorian can't.

[Ed Lizard]

Chantal survived?

 

Anyway, Dorian is still producing some cold cloud tops, but it just doesn't 'look' right and if it still has a closed low, it just barely still has a closed low.

[AvantHiatus]

Chantal survived?

 

Anyway, Dorian is still producing some cold cloud tops, but it just doesn't 'look' right and if it still has a closed low, it just barely still has a closed low.

It's debatable but Chantal retained a semi-coherent low level circulation before the Eastern Caribbean and land interaction with Hispaniola finished it off.

[wxmx]

83, 88 and the unmentioned but 'slow' 1992 may not have had action before August 1st, but all had serious red meat storms hitting or barely missing the United States.  Quality trumped quantity. 

 

 

Anyway, silver lining again, new GFS sort of like 6Z FIM, could a remnant wave of Dorian drift Westward and bring rain to Texas?  We really haven't had a real Easterly wave type rain event yet this year.  Not sure looking at the GFS rain with Dorian's corpse would get here, but something to hope for.

 

 

Just looked at vis loops again with lat/long turned on for reference, and I see no signs of West winds in low clouds South of Dorian already,  48 hours to degeneration back to an open wave might be generous.

According to the latest ASCAT, the area of westerly winds is very limited, so it might be very difficult to detect any westerly moving low level elements. Also, this is in the brink of opening up, but without hard data, it's impossible to  tell so.

[wxmx]

Upper level conditions will remain mostly the same until after it gets loose of the TUTT's grip plaguing the C and W Atlantic...and that's west of 75W

[phil882]

It's debatable but Chantal retained a semi-coherent low level circulation before the Eastern Caribbean and land interaction with Hispaniola finished it off.

 

Perhaps the most interesting aspect of Chantal demise was the very well organized set of arc clouds that emanated outward from the low-level circulation at the same time the well organized llc that was observed by Martinique radar was collapsing. Most of you know that arc clouds are a clear sign of dry air near the low-level circulation which is not a favorable environment for development. However, very well defined and extended sheets of arc clouds like this could be a deterrent for another reason, as they force ascent in a band well away from the small llc, which could cutoff inflow and dissipate an already weak circulation.

 

 

 

We appear to be seeing a less pronounced version of the same arc cloud dispersion with Dorian today (note the linear band of clouds near 45W.