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WxWatcher007

Hurricane Isaías

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Just looking at the visible satellite pictures and nothing else earlier today I thought it was the SW blob of the axis that had the most spin look.  Now that convection is dying and it looks like that NE blob is taking over.  Such a huge area of disturbed weather.  It will be interesting to see how this plays out.

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Reads-info sharing looks very good-helpful, especially recon and newer model science (PV). My written material is old science-rules of thumb and can be misleading (i try to realize that in my posts). 12z/28 cycle: trends are drawing a "little more" consensus... recurve somewhere along eastern seaboard, even if into GMEX (i.e .I see the EC starting recognize the system--slightly). UK is now onto this as a pretty strong storm at 144 hrs along with cont'd GGEM brutus. Somewhere in the middle of all this has to be an eventual reality, a week in advance. I still focus up here in NYC area on moisture contribution this Sunday-early Wednesday and possible rip current interruptions of ocean swimming. Following NHC and their science as well as ensembles etc. 

One note: I saw the troll post.  imo,  some of us like lead time on possible travel plan adjustments. That means we have to provide information that is reliably accurate in a broad sense.. at least 5 days in advance, to be potentially helpful in planning.  At this point... would you risk a non pandemic cruise off the east coast Sunday-Thursday, especially with some mariners tending to not realize downside-vulnerability to their vessel.  Not I.  I think we have enough examples in the past 15 years where there was plenty of advance information that suggested stay in port or avoid and the failure to do so resulted in deaths-injury. This is why there is discussion outside official channels. Not to hype but realize something is available that we may consider useful.  For me it's water...portions of extreme nw NJ have missed last weeks big rains.  We can benefit from a sizable recharge.

Keep the humbled information flow going, always realizing it's only modeling and our biases of interpretation. 

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2 minutes ago, wxeyeNH said:

Just looking at the visible satellite pictures and nothing else earlier today I thought it was the SW blob of the axis that had the most spin look.  Now that convection is dying and it looks like that NE blob is taking over.  Such a huge area of disturbed weather.  It will be interesting to see how this plays out.

During their flight recon seemed to find the better shifts in wind (although broad) further north. As that burst of convection continues and that eastern lobe of convection wanes or rotates northward, I think we see the consolidation necessary to give us Isaías.

I really don’t think we can hone in too much on track or intensity yet, but we do have some broad stroke ideas to rattle around here.

1) the ensemble guidance likes to put this in the Bahamas by Friday or Saturday. There hasn’t been much deviation there, even with the operational runs. From there I agree with wdrag that there’s some type of curve coming as that ridge and possible trough steer this northward. This isn’t going to trend to Louisiana IMO. My speculative thought is that the FL panhandle to OTS after a close SE call and obviously anything in between is the range of possibilities in my head. 

2) The system has three main challenges: dry air by a close proximity SAL, wind shear, and possible land interaction with Hispaniola. That means that we’re unlikely to see an all systems go type intensification for a while. These are all things that can change though. Any resilient core could increase the intensification ceiling.

Like the NHC, we’re in wait and see mode. Like I said yesterday, I think the best way to track this right now is to use the ensembles to track deviations in the upper level steering pattern, the radar/satellite data to discern 6-12 hour trends with the system itself, and the operational guidance for weenie fodder :D

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2 hours ago, WxWatcher007 said:

During their flight recon seemed to find the better shifts in wind (although broad) further north. As that burst of convection continues and that eastern lobe of convection wanes or rotates northward, I think we see the consolidation necessary to give us Isaías.

I really don’t think we can hone in too much on track or intensity yet, but we do have some broad stroke ideas to rattle around here.

1) the ensemble guidance likes to put this in the Bahamas by Friday or Saturday. There hasn’t been much deviation there, even with the operational runs. From there I agree with wdrag that there’s some type of curve coming as that ridge and possible trough steer this northward. This isn’t going to trend to Louisiana IMO. My speculative thought is that the FL panhandle to OTS after a close SE call and obviously anything in between is the range of possibilities in my head. 

2) The system has three main challenges: dry air by a close proximity SAL, wind shear, and possible land interaction with Hispaniola. That means that we’re unlikely to see an all systems go type intensification for a while. These are all things that can change though. Any resilient core could increase the intensification ceiling.

Like the NHC, we’re in wait and see mode. Like I said yesterday, I think the best way to track this right now is to use the ensembles to track deviations in the upper level steering pattern, the radar/satellite data to discern 6-12 hour trends with the system itself, and the operational guidance for weenie fodder :D

I believe NASA expects the current space station Dragon crew to return to earth this weekend, albeit close to Florida. Will this be impacted by this storm?

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29 minutes ago, etudiant said:

I believe NASA expects the current space station Dragon crew to return to earth this weekend, albeit close to Florida. Will this be impacted by this storm?

The storm is forecasted to be closest to Florida this weekend so if there is a return there it may be impacted. I thought all shuttle crews returned via California or Texas though. 

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Just now, WxWatcher007 said:

The storm is forecasted to be closest to Florida this weekend so if there is a return there it may be impacted. I thought all shuttle crews returned via California or Texas though. 

Used to be that way when NASA was running the show. Not sure how they are returning with Musk in charge.

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53 minutes ago, etudiant said:

I believe NASA expects the current space station Dragon crew to return to earth this weekend, albeit close to Florida. Will this be impacted by this storm?

Yes, this needs to be watched as recovery is risky in high swells.   This is no shuttle, they splash down like the Apollo days.

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Definitely messy right now but as @csnavywx stated this big convective burst can help focus things. We’ll see when things stand when recon arrives in a few hours. 

A durable MCV could go a long way toward getting this thing going.

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It looks like it's definitely moving more NW rather than WNW in the last hour or so.  It's gained a few degrees of latitude in the past couple hours.

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6 minutes ago, cptcatz said:

It looks like it's definitely moving more NW rather than WNW in the last hour or so.  It's gained a few degrees of latitude in the past couple hours.

What has? There is no defined center

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5 minutes ago, Yeoman said:

What has? There is no defined center

The overall system.  At least to me it seems.

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The NHC discussion was excellent with something I’m very intrigued by. @Windspeedwas getting at this a bit before. Position the system properly relative to the shear mechanism (ridge or trough) and you get a neutral if not favorable environment. Something to watch closely. The PV streamer matters much less if this can organize well—which is far from certain if this tracks over Hispaniola.
 

The intensity forecast remains problematic for primarily two 
reasons: 1) the lack of a well-defined center and inner-core wind 
field and 2) likely land interaction to some degree. In the 
short-term, a bonafide center could develop tonight in response to 
the expected development of intense convection caused by orographic 
forcing by the mountainous islands of the central and northern 
Leeward Islands. Once a center closes off, which has likely been 
inhibited from doing so due to the disturbance's fast forward speed 
in excess of 20 kt, the low-level convergence will improve and 
convection will become more organized and symmetrical, allowing for 
strengthening to occur. The main question is how much land 
interaction with Puerto Rico and Hispaniola will disrupt the 
circulation in the 36-48-hour period. Assuming the system remains 
intact after emerging off the coast of Hispaniola, the slow track 
over the very warm waters of the Straits of Florida would result in 
more strengthening, assuming the system doesn't interact with the 
Cuban landmass. Although the GFS-and ECMWF-based SHIPS intensity 
guidance shows considerable southwesterly vertical wind shear of 
20-30 kt in the 72-96 h period when the disturbance is over the 
Straits, the global model fields show that this is self-induced 
shear caused by the SHIPS model incorporating the system's 
impressive upper-level outflow winds in its shear calculations. As a 
result, this is not being considered a negative intensity factor 
compared to land interaction. Due to aforementioned uncertainties, 
the new NHC intensity forecast remains on the conservative side, and 
lies between the slightly weaker IVCN and stronger NOAA-HCCA 
consensus models. Interests in Hispaniola, the Bahamas, Cuba, and 
Florida should continue to monitor forecasts as changes to both the 
track and intensity are likely.

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This is starting to look like a classic shredderolla.    It starts to get it's act together, then goes right into the southern coast of it. It's never seen or heard from again.

 

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24 minutes ago, Amped said:

This is starting to look like a classic shredderolla.    It starts to get it's act together, then goes right into the southern coast of it. It's never seen or heard from again.

 

Not so fast

 

AL09_2020072900_GEFS_large.png

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1 hour ago, MJO812 said:

Not so fast

 

AL09_2020072900_GEFS_large.png

Most of those ens tracks are shedders, unfortunately

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2 hours ago, Dr. Dews said:

Most of those ens tracks are shedders, unfortunately

Correct me if I'm wrong...but if it *has* to go over Hispaniola - that's the best path. There's lower elevations (relative to other parts of the island under that mean and most of the ens tracks.

 

image-asset.png

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Good morning, 00z/29 Wednesday EPS/GEFS 500MB wind fields (still 12z/Monday the 3rd as yesterday), and tracks of the still limited center/location. Still looks like recurve to me and for now seems to be modeled as a marginal TS (lots of land interactions along the way?). It's "potential" main impacts up here in the NYC forum appears to be increased moisture and rip current risks (haven't looked at tides- but for an as yet an unnamed still uncertain track, just have no confidence on that tidal aspect). Will monitor NHC and all our forum contributors/discussion. I like the 500 mb wind speed cores and the general 850 wind field (not shown here) for us. WPC seems to have 1.5-3.0 inches of rain in their products for the NYC forum early next week. The ~52 member NAEFS continues focused along the eastern seaboard. One small downside..while there is yet option for GMEX to interior se USA, i could  easily see a hard right out to sea recurve  after getting to ~Virginia's latitude...presuming it survives that far as an 850 vort max. 626A/29

Screen Shot 2020-07-29 at 5.50.24 AM.png

Screen Shot 2020-07-29 at 5.51.41 AM.png

Screen Shot 2020-07-29 at 5.55.04 AM.png

Screen Shot 2020-07-29 at 5.55.55 AM.png

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418391554_COD-GOES-East-regional-prregional.airmass.20200729.101019-overmap-bars.thumb.gif.3ab759d4e36f53a48863e2691fe64000.gif

tell me this PTC.........doesn"t become an ODB    rappin up

1551727853_COD-GOES-East-global-atlantic_13.20200729.102019-overmap-bars.thumb.gif.89ee361b9eb4cf665f1a0c132fcb4585.gif

 

Mutt and Jeff right behind.......

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So here’s where I think things stand this morning:

77616615.gif?0.9995642399052285
 

In the last few hours, it looks like PTC 9 has been trying to consolidate a more robust mid level circulation around the persistent burst of impressive convection just west of Dominica. This has resulted in slightly higher winds and a continued gradual pressure drop. While this is a step in the right direction toward developing a closed LLC, as we see from radar and the image above, there is still a major issue. 

The overall wave is still tilted from SSW to NNE. The NHC mentions that in their 5am discussion and it’s evident above. Absent a more circular/symmetrical appearance, any organization will be gradual. We see progress but a lack of organization on the radar.

KcLeFYM.jpg

However, the continued convective burst is likely to continue, and as a result, I do think we’ll get a surface low in the next 6-12 hours if things persist. That should give us Isaías. Something to watch today is whether this can consolidate and get a poleward tick as a stronger system.

That brings us to the next stage of the forecast. Yesterday I listed dry air as a key challenge for development and intensification but I feel differently today. Despite lurking shear and SAL, PTC 9 has developed a solid pocket of moisture that should serve it well as it moves westward. 

JojlZzf.jpg

The biggest challenge by far is the evolution of the track. Will PTC 9 be able to avoid the high peaks of Hispaniola? As @Kmlwx points out above, there are parts of the island that have lower elevation. Should the center cross those NE areas or stay just offshore, a major hurdle will be overcome. Some of the ensemble guidance does this and the result is a stronger system more capable of combating shear in the western Atlantic.

A trek over the more mountainous terrain would effectively destroy the organization of the system and given how large it is, it is hard to envision any meaningful recovery, especially if shear is present. 

Not much can be known about possible US impacts until we have the answer to the land interaction question, but the steering pattern seems increasingly favorable for US impacts.

The ridge still looks rather dominant, pushing whatever we have into the Gulf, Florida, or somewhere along the eastern seaboard. With stronger solutions (anything above low end hurricane) out of the picture for now, this just increases that risk. OTS is still possible but it seems increasingly unlikely to me. 

Bottom line, the overall organization of PTC 9 is improving and I expect a TS today. We are still emphatically in wait and see mode until we have a center and course trajectory over the Greater Antilles. If the system is able to avoid significant damage over Hispaniola, the US threat increases due to the currently modeled steering pattern.

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15 hours ago, FLweather said:

Agree. Same view here. I see it potentially entering the GOM.

Really though just judging by satellite might actually be two separate areas instead of one broad area. 

 

The trough that ultimately causes recurve is modeled across guidance and is deep ...the recurve will very likely happen...but my bet is this interaction begins taking place across western Cuba tracking the storm into the eastern Gulf of Mexico with best chances from LA to Panhandle of Fla...Just my current long range thoughts...

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This looks bad for Hispaniola regardless of TCG, as strong southerly low-level convergence along the axis right over the mountains with orographic ascent/forcing is going to put down some extreme rainfall as it passes over. This comes into play as the axis becomes aligned more poleward.

 

The area due west of Dominica still looks most suspicious for cyclogenesis in the short-term, if it's going to occur sooner than later.70e218cef715ebc3b178b16cda7f8a2e.gif&key=2e6cccc8a6c0a4c658bd3f67d4ae54788ba4ffcb3fc84909b3401e7b2559deea

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This looks bad for Hispaniola regardless of TCG, as strong southerly low-level convergence along the axis right over the mountains with orographic ascent/forcing is going to put down some extreme rainfall as it passes over. This comes into play as the axis becomes aligned more poleward.
 
The area due west of Dominica still looks most suspicious for cyclogenesis in the short-term, if it's going to occur sooner than later.70e218cef715ebc3b178b16cda7f8a2e.gif&key=2e6cccc8a6c0a4c658bd3f67d4ae54788ba4ffcb3fc84909b3401e7b2559deea
Recon finds no low level center, but...17df678aecabe8c4eaa9bf07673b31d7.jpgc720a9eab67b351db356243adc319477.jpg

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