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2021 Atlantic Hurricane season


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17 minutes ago, MJO812 said:

Good luck getting anything in the US with the troughs that are modeled. 

If, as GFS most runs and about half the ensembles, have a TC in the Gulf in 8 or 9 days, trough position only means is it Texas/Mexico, Louisiana/Mississippi, or Alabama/Florida?  Little escapes the Gulf.   Northeast US, late September (1038), late October (Sandy), just off top of my head, and I am sure as the pattern transitions to Autumn, steering will be constantly changing.  Oh, empirical MJO prediction has been fairly good this year, Florida could have an interesting October from Caribbean systems,.

EWP_Oct.PNG

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4 minutes ago, Ed, snow and hurricane fan said:

If, as GFS most runs and about half the ensembles, have a TC in the Gulf in 8 or 9 days, trough position only means is it Texas/Mexico, Louisiana/Mississippi, or Alabama/Florida?  Little escapes the Gulf.   Northeast US, late September (1038), late October (Sandy), just off top of my head, and I am sure as the pattern transitions to Autumn, steering will be constantly changing.  Oh, empirical MJO prediction has been fairly good this year, Florida could have an interesting October from Caribbean systems,.

EWP_Oct.PNG

Agree

Troughs will become deeper as we head into October which can spell trouble if one phases with a trough.

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1 hour ago, MJO812 said:

He never learns 

This  idiot seems to agree with me. I said a  month ago Sept would be suppressed. We are all often wrong including those who said the  pattern in the  peak season was  "ominous" for the east  coast. Turned  out  just the  opposite.

 

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13 minutes ago, ldub23 said:

This  idiot seems to agree with me. I said a  month ago Sept would be suppressed. We are all often wrong including those who said the  pattern in the  peak season was  "ominous" for the east  coast. Turned  out  just the  opposite.

 

This tweet from Dr. Ventrice is strongly misleading IMHO.
 

 

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 There’s no suggestion Sept will turn out quiet. First, Larry is looking to end up being a hurricane for 10+ days and a MH for most of that period. In terms of ACE, that’s strong activity by itself….lots of energy for the first 13+ days of the month! Second, if the EPS has the right idea, there will be only a couple of days between the demise of Larry and the next MDR system or two. Third, there’s the threat of Gulf activity over the next 10 days or so. That may produce 1-2 more TCs. Fourth, ensembles go out only through 9/20. That still leaves 1/3 of the month that can’t even be seen yet. Fifth, there usually are one or more TCs that aren’t even hinted at far in advance on models. Sixth, there’s still the very real chance of a far eastern MDR TC, sharp recurve or not, near 9/11-12 from the suggested very strong AEW still forecasted over Africa in a few days and then moving offshore ~9/11.

 So, there really is no indication of anything less than an active Sept based on objective measurements.

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I can't follow the forecast GFS Gulf system back w/ 850 mb vorticity, I *think*, following PW back, this might be the origin of the system the GFS develops.  It reaches the area of higher vort/already high PW (edit- in far S Caribbean/coast SA), merges, and something develops.  Looks harmless now.

MidmonthGulfSystem.PNG

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Per the 12Z GFS and CMC, that strong AEW over Africa that especially the Euro but also the ICON have been developing on 9/11 just offshore never recurves but instead stays weak and moves WSW in the E Atlantic. You can actually trace the vorticity/precip associated with it on the 12Z GFS then move W all of the way to the Lesser Antilles on 9/17 followed by it moving WNW into the Caribbean but staying very weak.

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46 minutes ago, Ed, snow and hurricane fan said:

I can't follow the forecast GFS Gulf system back w/ 850 mb vorticity, I *think*, following PW back, this might be the origin of the system the GFS develops.  It reaches the area of higher vort/already high PW (edit- in far S Caribbean/coast SA), merges, and something develops.  Looks harmless now.

MidmonthGulfSystem.PNG

Seems to me that convection is not directly related to what the GFS develops, but just some thunderstorm activity with no real convergence.  If you look carefully at the GFS vorticity, it looks like the system the GFS forms in the W. Caribbean is the combination of a tropical wave currently in the SE Caribbean between Curacao and Trinidad, along with a vorticity spoke extending SW from Hurricane Larry.  See satellite wind analysis below to see the weak convergence associated with the tropical wave. 

(As you probably recall, I described the process by which a new tropical cyclone can form from a vorticity spoke extending SW from a recurving TC in this thread:) 

Trop wave SE Carib.png

gfs_z850_vort_watl_fh-72-144 (1).gif

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6 hours ago, cptcatz said:

GFS and Euro are trash in the long term. How do you still base your opinion on their 10-15 day forecast? It makes you look like an idiot after you're wrong time after time. 

It’s the Greatest failure of the internet.  Instead of increasing the opportunity for greater information exchange it spawns trolls who contribute zero but get their loser shits  and giggles from interrupting serious and solid exchanges of truly valuable info. 

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31 minutes ago, GaWx said:

Per the 12Z GFS and CMC, that strong AEW over Africa that especially the Euro but also the ICON have been developing on 9/11 just offshore never recurves but instead stays weak and moves WSW in the E Atlantic. You can actually trace the vorticity/precip associated with it on the 12Z GFS then move W all of the way to the Lesser Antilles on 9/17 followed by it moving WNW into the Caribbean but staying very weak.

The plot thickens... there is clearly an upper trough/weakness in the subtropical E Atlantic that has been trending stronger past few days, but only a stronger system would really feel the effects of this.  GFS has that trough as well and it's even deeper than the ECMWF, but a sounding clearly shows mainly easterly winds from 500 mb and below around the tropical wave as it comes off the African coast, with SE winds above 500 mb. (Note it comes off the coast about a day earlier then the ECMWF).

The ECMWF/EPS have a known significant bias to show "landcanes" that are too strong inside W Africa and then coming off at an unreasonably high latitude.  This bias was on display seen even with a relatively weaker wave like the one that is just moving off the African coast today.  See how ECMWF trends about 350 mi SW with the center of vorticity vs. runs three or four days ago.
 

ecmwf-ens_z500aNorm_eatl_fh144_trend.gif

ecmwf_uv850_vort_eatl_fh24_trend.gif

GFS sounding E Atl Sep 11.png

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4 hours ago, ldub23 said:

This  idiot seems to agree with me. I said a  month ago Sept would be suppressed. We are all often wrong including those who said the  pattern in the  peak season was  "ominous" for the east  coast. Turned  out  just the  opposite.

 

That guy also said September 2017 would be dead and... It wasn't

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52 minutes ago, jconsor said:

The plot thickens... there is clearly an upper trough/weakness in the subtropical E Atlantic that has been trending stronger past few days, but only a stronger system would really feel the effects of this.  GFS has that trough as well and it's even deeper than the ECMWF, but a sounding clearly shows mainly easterly winds from 500 mb and below around the tropical wave as it comes off the African coast, with SE winds above 500 mb. (Note it comes off the coast about a day earlier then the ECMWF).

The ECMWF/EPS have a known significant bias to show "landcanes" that are too strong inside W Africa and then coming off at an unreasonably high latitude.  This bias was on display seen even with a relatively weaker wave like the one that is just moving off the African coast today.  See how ECMWF trends about 350 mi SW with the center of vorticity vs. runs three or four days ago.
 

ecmwf-ens_z500aNorm_eatl_fh144_trend.gif

ecmwf_uv850_vort_eatl_fh24_trend.gif

GFS sounding E Atl Sep 11.png

 

Interesting thoughts!

 And just like that, the 12Z Euro doesn't recurve it. Instead it starts out like it will recurve, but then it turns back W, then WSW, and then SW while weakening. Also, it comes off about 12 hours earlier than the prior run and closer to the timing of the GFS/CMC though still slower than those. These run to run changes and model differences show me that it is still too early to make a definitive call on what this AEW moving off ~9/11 will or won't do. After all, it is still ~6 days away from the coast and a lot can change before then.

 

Old Euro run (0Z) is along the African coast moving back inland to the NE:

ecmop_00_h500_ta_h_0192.png.699288a6b0e7eb6cfd714ce884f1536c.png

 

New Euro run (12) is 400 miles to the WSW about to turn SW and weaken:

ecmop_12_h500_ta_h_0180.png.f0bb0b9d57861ac9dbda4c49b01cad4b.png

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14 hours ago, GaWx said:

0Z EPS is still very active in the MDR late in the run/something  to watch for late Sept:

1488850626_ecmen_00_mslps_ta_h_0360(2).png.ff1f6152961e728070c0425c1eacb965.png

12Z EPS for same time is not nearly as active as 0Z run: 

(Edit: But regardless, I'm still keeping a wary eye on the vigorous AEW progged to move off Africa near 9/11. Earlier in this run, you can see a significant SW shift in the mean of this wave along with an increase in the number of members that don't recurve and instead that turn WSW vs the 0Z run.)

 

ecmen_12_mslps_ta_h_0348.png.d8c55bdcc1ee0d9bca4177c14916bff6.png

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On topic- 18Z GFS suddenly spins up 91L in 3 days (not a closed low yet).  No idea what happens after, 500 mb pattern, it will get swept quickly off the East Coast, I suspect, if it develops much at all.

 

Long Island born (Doria, Belle) and live in Houston (Allison, Rita scare (12 hours no power, MIL lost her fruiting avocado tree, but nothing like expected locally) Ike, Barry (no rain, but winds started serious wildfires W of here), then TS Harvey and Imelda), I lose local interest, because, Freeport in 1940s and Jerry as exceptions, season ends with Equinox, but 1938 was an obsession growing up, Sandy, of course (missed Gloria in the Navy), I stop looking for 10 day storms in 3 weeks, but I'll follow any ECUSA threats all year.  Then Nor'Easter season.  1978 alone, 2 school cancelling storms.  Still very excited, but no power for 2 weeks after Ike, people at my church dying in Harvey, relatives flooded out by Allison, now more love/hate confliction now.

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1 hour ago, Ed, snow and hurricane fan said:

W Car system is so far South it crosses BoC quickly, and doesn't develop.

Only a couple of GEFS disagree, no W Carib threat to the Gulf in a week-10 days, a Beta type school cancelling for a day system would have been fun, but now looks like we survive the Equinox, the unofficial (1940s and Jerry, yes, I know) end of Texas season,  a week w/o electricity, no adrenaline this year, but no power sucks.  Louisiana to Maine, season still happening.

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The same strong AEW currently over central Africa that the models have for many days been having move off 9/10-11 and becoming a TC almost immediately on a number of Euro and Icon runs is the strongest on the new GFS run that I can recall. Even though it weakens, it is now the 3rd GFS run in a row with a trackable AEW getting into the Caribbean 9/17 and is the most energetic it has been when getting there (strong wave). This once again gets to Cuba/FL Straits/S FL late on 9/20 and tells me once again that this could conceivably threaten the Caribbean ~9/17-20 followed by the CONUS starting ~9/20.

Climo says that a scenario like this isn’t at all far-fetched for an AEW moving off ~9/10, especially in La Niña.

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The 6Z GFS/GEFS and EPS are continuing the idea that the AEW moving offshore Africa 9/10 (GFS) or 9/11 (Euro) (is the same AEW) may very well eventually be something to contend with. The 6Z GFS is the 4th run in a row that gets it near FL ~9/20 as a strong wave. Also, this run suggests there may be another active wave a few days behind it. In addition, note the strong E US ridge being suggested for around that period.

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A convergent boundary has setup in place north of the Yucatán that is associated with 91L's northern axis. Low level flow is southerly but with an absence of any notable cyclonic rotation. However, if this boundary can persist with strong convection and increase the gradient, an MCS may develop, which could increase potential of development as the feature drifts north into the central GOM. Shear appears too strong over the BOC for anything to get going for the original low pressure. If something is to organize, it's going to be out of that region of strong low level convergence.bd3b7a95ecbf050cda379acde9941796.gif

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Here we go regarding that same AEW moving off Africa ~9/11:

1. ICON has it stronger and further out than earlier runs as it moves west at the end of the run. It is already pretty far north at 20N, which would suggest a good chance at an early recurve, but keep in mind that the models are jumping around as they try to figure out how strong this AEW will be and where it will track as evidenced by lots of run to run changes

icon_mslp_pcpn_eatl_60.thumb.png.3e89333153796c7b94a42e67e250544c.png

2. UKMET finally has it as it just moved to within its 144 hour range. This track, too, would mean a likely early recurve but note that this has it a TS right off Africa and a near H within 24 hours, both of which could be too strong:

 NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 120 HOURS
              FORECAST POSITION AT T+120 : 15.6N  15.7W

                        LEAD                 CENTRAL     MAXIMUM WIND
      VERIFYING TIME    TIME   POSITION   PRESSURE (MB)  SPEED (KNOTS)
      --------------    ----   --------   -------------  -------------
    1200UTC 11.09.2021  120  15.6N  15.7W      998            39
    0000UTC 12.09.2021  132  17.3N  18.7W      992            50
    1200UTC 12.09.2021  144  18.9N  20.6W      983            57

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12Z GFS is the 5th run in a row taking this same 9/10-11 emerging AEW into the Caribbean ~9/18 as a result of it staying weak. This wave is what is causing the convection at the Lesser Antilles on the far right in this image:

gfsop_12_p850ts_gc_h_0294.png.340520a8284fdf6f58357b82ba06eb8b.png

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