Windspeed
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Everything posted by Windspeed
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You're going to come off as quite bipolar in your postings if you start hanging on each GFS operational run for long-range track and immediately making a declaration of death in your "outlook" of the upcoming period every time that track doesn't pan out. The very next run could have an entirely different TCG location and resulting stronger track intensity ~120 hrs out. Best to just realize we have potential development to follow. The ensembles are still more valuable in the long range as has already been stated multiple times, repeatedly. When we actually do have a TC to track, we then may start focusing more on operational track placement and pattern, though you still must be cautious beyond 144+ hrs for the downstream pattern, as that can easily flip. At any rate, your persistent declarations about the peak season being this or that based on single operational model outputs every six hours is not particularly contributive to the discussion. That's not to say we should not point out a pattern that swings more unfavorable. But that is entirely not what is being suggested by modeling here in the mid-to-long range.
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Thought that was already deemed 98L. Sometimes they'll discuss them as ALxx. Former NHC Specialist Kimberlain referred to the disturbance as AL98 earlier. At any rate, unsurprisingly the GFS weaker in the mid-to-long range with the potential TC due to tracking through the Greater Antilles and timing/position being not as aligned with strong upper ridging. That upper ridging is a beast though and is probably more the takeaway; i.e., IF a TC gets positioned under that, things could escalate quickly.
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NW periphery of 97L's wave axis is now moving through the Windward Islands of the Lesser Antilles. Nothing immediately eye-opening yet. Convective showers and storms embedded in strong easterly flow around the wave. If something within the axis begins to fold, it's likely to be a tick east and not coming into range of radar until later this evening.
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Nice post by Todd Kimberlain. My takeaway here would be AL98 staying relatively weak regardless of TCG until it begins to approach the Lesser Antilles. Lower steering flow will begin to align more with upper steering flow, which would likely allow the system to stack better vertically. The GFS has been a little wonky with convective feedback over the EPAC in the long-range, given some of the oddball convective spin-ups after Genevieve considering the shift of upper 200 hPa vorticity eastward; yet it continues to show a mighty large upper ridge / anticyclone developing over the Caribbean and GOM late in the period, which could spell trouble if a hypothetical TC is moving through the region. There is also a strong STJ that splits flow and ejects eastward over the Southern CONUS. That would seemingly decrease upper level westerlies over the NW Caribbean and GOM downstream. Again, this all means squat if there is no TC there to take advantage. I am still apprehensive of the GFS right now. So take the strong fantasy Caribbean runner with a grain of salt until we actually have a TC to track.
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In the short-term, the wave just east of the Lesser Antilles does have weak vorticity and increasing convection, especially on its SW axis. Some of last night's EPS showed potential development of this disturbance, though today's 12z ECMWF operational keeps this open into central America. The 12z UKMET and GEM operationals are much more forgiving and do want to produce a TC as it traverses the deep Caribbean. No need to mention the 12z GFS since @Idub23 has that covered into September. [emoji6]
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12z ECMWF now runs a TC, presumably the AEW that just exited Africa, just north of the Antilles through the Florida Straits and deep into the Gulf. Extends WAR and builds heights. Obviously this is way out in fantasy long range, but we now have a major operational model coming into line with its ensembles. Was only a matter of time. Now we'll just have to be patient and see how TCG occurs and where. Additionally how the upper pattern will unfold as any potential systems reach the WATL. We are too far out to know if any particular potential TC will aligned under a favorable or unfavorable setup. A lot of variables and a lot depends on downstream TUTT evolution, split and where those upper heights build specifically. Overall takeaways should just be increased potential for a long-tracking TC out of the MDR and notable WAR extension.
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Long range European ensemble continues up...
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Andy commenting on the EPS and Caribbean potential in the ~200 hr range. Note the powerful upper ridge being modeled over the Caribbean. Granted, the operationals do not have a TC under this feature yet. They may of course never. However, the EPS ensembles do and also have that upper ridge. Depending on TC placement, of course, that would support a powerful TC from the S. Bahamas to the NW Caribbean barring land interaction. Obviously this doesn't mean Jack Squat if there's no TC. But that's why you watch the ensemble packages for potential vorticity. At any rate, with MJO coming aboard in that range, this is all we've got until the ops do eventually start getting into closer range to better resolve something and we can see how those runs will start panning out.
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You don't really focus on strength, you focus on signatures. That there are numerous possible tropical lows means potential increases for something to be somewhere favorable or unfavorable. At ~200 hrs all your looking for are potential low placements. Then you go back and analyze the possible upper environments for those areas. At some point an operational will start picking up on any one sig. At that range it is still a crapshoot, however. You're just looking for more potential area of interest and then analyze the pattern to keep looking for something to rear its ugly head in the ops.
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Speaking of ensembles... [emoji102]
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Then you would be failing to see or underselling the favorable atmospheric conditions that were developing over Hanna and over the western GOM. It just ran out of time to see that potential through.
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That already occurred the last week of July and first week of August. We had a two week stretch that had two hurricane landfalls. Were conditions perfect for a major? No, but Hanna would have been a major given 6 to 12 more hours over the western GOM. It was a very well-developed hurricane intensifying right up to landfall with a symmetrical eyewall. Would that being a major hurricane at landfall really change the conversation about this quieter stretch? Not really in my opinion. We'd still have some struggling systems until conditions flip to more favorable in the coming weeks. Again, it's August 13th.
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Are you seriously asking that question? Do you even read this thread? lol... Hell.... Kill me...
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TAFB/NHC has issued a code yellow for a weak disturbance near the North Carolina coastline that is forecast to move ENE in the coming days with 20/30 probs. It does have weak mid-level vorticity and could take on more tropical characteristics in the coming days as the system moves out into the open Atlantic. ZCZC MIATWOAT ALL TTAA00 KNHC DDHHMM Tropical Weather Outlook NWS National Hurricane Center Miami FL 200 PM EDT Thu Aug 13 2020 For the North Atlantic...Caribbean Sea and the Gulf of Mexico: The National Hurricane Center is issuing advisories on recently upgraded Tropical Storm Josephine, located over the tropical Atlantic Ocean several hundred miles east of the Lesser Antilles. 1. A low pressure area over eastern North Carolina is expected to move east-northeastward across the north Atlantic well to the south of New England and the Canadian Maritime provinces for the next several days. This system could acquire some subtropical or tropical characteristics during the next two to three days while it moves over warm sea surface temperatures. * Formation chance through 48 hours...low...20 percent. * Formation chance through 5 days...low...30 percent. Forecaster Beven
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Has anyone said it was? Seems like most, including myself in recent posts, have gone to great lengths to cite the differences. Yet, ACE is still more than double climatological average for this date. It's also just Aug. 12th and we've had two hurricane landfalls in 2020 in addition to an ongoing TCG during an unfavorable period. You keep harping a specific operational model, in this case the GFS in the long-range, over and over again. I am uncertain why you are trying to climb upon this hill which to die. It's premature to do so a month prior to climatological peak. Counter arguments already established in this thread that we are in a less active period. It is too early to be locking down on a 240+ long-range operational output to make heads or tales of what will or will not occur versus just utilizing climatological modeling tools that such scenarios are better intended and better suited, such as ensemble precipitation guidance, long-range pattern and oscillation modeling, which do suggest a ramp up of activity across the Atlantic Basin in a few weeks.
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Last night's ECMWF ensembles were picking up on a AEW in the 7-10 day range and developing it near the Northern Leeward Islands. To be honest, the operationals have not been the greatest this year on TCGs. The GFS op even ghosted a CA monsoonal gyre last week and went so far to produce a fantasy GOM hurricane over many consecutive runs. Odd fantasy TCGs aren't unusual, but entire monsoonal gyres are. They also have not handled positioning of upper 200 hPa vorticity well for convection. So the GFS may've just had that too far displaced east over the Caribbean. WPAC TCG has been off as well in the operationals. At any rate, complaining aside, I'm not sure if it's a lack of global flight data or just bad luck. We're still in the long range for improving pattern and environmental factors in the 10+ day range, however. You want to focus more on ensembles in the long-range and ops for short-term TCG. But even in the short-term, the ops haven't been great.
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Isaias was a fast mover and the depth of the 26° isotherm is very anomalous off the SE CONUS this year. It's been a very hot Summer with limited cloud cover and few stalled boundaries, especially over the past 30-40 days. Everything on the shelf is above 26°C now based on AOML; and since the shallow layer for SSTs is only 25-30 meters at depth, it essentially is anomalously warm right up to the shoreline. Though keep in mind, the isotherm map isn't on the same scale, as the shallow shelf is only 50 meters deep at interaction with the Gulf Stream, where, at that point, it drops well below 100 meters on a much higher gradient extending ESE. This may also be throwing off the TCHP map as depth of 26ºC isotherm is one of the data sets along with immediate surface layer temperature profiles. In past years, the shallow shelf was hardly represented by the 26º isotherm. Perhaps in recent years this was changed in the way data was displayed; however, if the entire shelf is above that isotherm, it should still be represented in the immediate surface layer at ~30 meter estimate. Though Isaias' low level circulation was amplified by a tropical low level southerly jet on its eastern semicircle due to trough interaction, it was really moving too fast and had too small an RMW to do anything but perhaps upwell and push ~28°C water from 50+ meters depth down the shelf near the Gulf Stream. The immediate landfall area did cool a few degrees, but that appears to be rebounding fast due to hot days + clear skies. Also recall that Isaias only managed to regain hurricane intensity very near the South Carolina shoreline. Additionally, it remained rather devoid of convection on its southern semicircle and struggled to mix down higher winds until interaction with the coast. Its windfield only expand near landfall with influence of the low level jet and baroclinic enhancement up the Mid-Atlantic coast. In comparison, Hanna was a slow mover with a much broader low level circulation as it traversed the Central GOM and had a large region of persistent intense multi-convective systems that did a number on the shallow layer heat content, not to mention some extended upwelling. But that's been several weeks ago and, unsurprisingly, the Central and WGOM immediate shallow layer is running ~29-31°C again.
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In a meteorological sense, it's called oceanic lag time. The ocean heat content always lags behind atmospheric mean temperature gain. It also takes time, even in the most favorable large scale patterns, for hurricane season to reach fruition.
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If I read you right, you're calling for 2 hurricanes and 1 major hurricane the remainder of the season? I mean that's fine but you realize it's August 12th? Climatological favorability across the basin doesn't normally kick in until around August 20th-26th even in active years. I think a lot of folks fail to realize how quickly an unfavorable synoptic and environmental pattern can transition to favorable. Shear issues appear to be short-term. The hostile westerly upper level flow across the Caribbean is due to the current convective outbreak in the Eastern Pacific. However, more favorable upper 200 hPa vorticity will shift to over the Atlantic Basin by August 20th. Westerly windshear will decrease as the EPAC swings into a more suppressed regime. Likewise the strong easterly 700 hPa windbursts that have driven SAL will back down as Azores SPHP shifts into a more SER/WAR extended pattern (as is typical does this time of year). As such, the MDR will moisten for the September run. Sub-800 hPa to sea level pressures have already been running lower than climatological mean. All these factors within consideration, I think some folks are going to be taken surprise during the peak regardless of the active to hyperactive forecasts.
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I am not making any adjustments. Signals still scream a crazy active peak that is prolonged through October with -ENSO and +AMO signals. Now how NAO evolves could influence deep Caribbean tracks versus more interaction with the Eastern Seaboard. WAR/SER should be in place through October though. There will still be westerly shortwaves and intermittent weaknesses for recurves. But several TCs will time under waxing extensional Azores-Bermuda ridging versus waning as troughs lift over New Foundland and Greenland maritimes with robust SERs rebuilding in place; therefore, I do not think we're staring down another 2010/2011 type active season where everything is central Atlantic based. I should specify peak MDR/CV stretch of season, as this season up to this point is entirely dissimilar. Perhaps something akin to 2004 and 2008 with enough blocking in place to drive some W. Caribbean and GOM systems like Ike, Gustav, Ivan, Felix, Frances, etc. Again, I want to avoid 2005 in comparison because, if you recall, after July we really did not have many MDR/CV long-tracking hurricanes that reached the far WATL. Katrina developed out of TD10 remnants in the Bahamas. Rita was home grown as well. Wilma was pure WCARIB post frontal and tropical wave interaction. All those other numbers were among a swarm of TCs that developed out in the middle of the central Atlantic. Again, with the pattern evolving, I will be surprised if we don't have at least a few hurricanes that eat up some longitude and become Antilles, Central America or SE Conus threats. Not saying it will be 2017 again, but can you imagine a 2017-like year in the MDR but with significantly greater longitudinal tracks?
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July of 2005 was so anomalous, I'm not sure it's even reasonable to compare ACE numbers to it. When you have two long-tracking major hurricanes that reached Category 4 and 5 prior to peak weeks, it remains a freak outlier in terms of ACE compared to even other hyperactive years. 2017, 2010, 2008, 2004, 2003, 1999, 1998, 1995 and so forth are much more in line climatologically speaking. This year so far has been more about numbers of named storms, though I do expect ACE to be skyrocketing in September this year regardless of hyperactive or just normally active.
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The would-be Josephine does have a good shot at hurricane intensity and could overperform during a 24 hour window. Easterlies back down and prior to TUTT development, upper divergent flow may create an environment for RI if only for a 12-hr period, but that could be enough. Still don't think I'd be bold enough to call for a Category 3 until we see a well-developed core. Stable 700 hPa Theta-E can break hearts. Regardless of intensity swings, Josephine will have a rough go beyond 72 hours when those westerlies start cranking. Here is Stewart's 5AM: The aforementioned unfavorable conditions of dry air entrainment and southeasterly shear are expected to give way to more conducive environmental conditions by 24 h when the cyclone will begin to move underneath the center of a synoptic-scale upper-level anticyclone. This will result in the shear decreasing to near zero, along with a pronounced improvement in the upper-level outflow pattern. The much lower shear conditions should also reduce the amount of dry air entrainment, while allowing for some moistening of the surrounding environment to occur. These more favorable conditions are expected to persist through at least the 60-h period, and thus slow but steady strengthening is forecast during that time. By 72 h and beyond, the global models and regional models show the system moving out from underneath the positive influence of the upper-level anticyclone, encountering moderate southerly to southwesterly vertical wind shear, which is expected to induce gradual weakening. It should be noted that during the 48-60 h period when the shear will be the lowest and sea-surface temperatures will be near 28.5C, there is a narrow window of opportunity where the intensity could peak higher than what is currently indicated. The new NHC intensity forecast is very similar to the previous advisory, and is slightly higher than the consensus intensity consensus models IVCN and HCCA due to anticipation of the very favorable low-shear conditions. I do think Josephine becomes a hurricane for a day, but it won't last long with that 30+ kts of shear blocking its path:
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You mean the season so far or just the hype? The season so far is not really indicative of the potential that exists in a few weeks. If we're hearing crickets by the second week of September, then I'd start considering a bust. Still, we have had two hurricanes already, albeit not a lot of ACE withstanding. Yet, more than double climatological mean for this date. At any rate, a busy four-to-five week stretch can produce a lot of hurricanes. Too many examples of that to even mention. You can look up most active years and see when they really took off. I would also add that as far as seasonal forecasts, a very real bust is certainly possible, though I think it is rather unlikely that we miss out on an active season. A bust for hyperactive forecasts is obviously still very much in play simply due to their rarity. That we had so many forecasts favoring hyperactivity is due to many favorable factors coming into play for the height of the season, which, we are not there yet. We're still waiting for all of those ingredients to produce. Also, bust or no bust, yes, we could have a nightmare hurricane landfall and if we do not reach sufficient ACE and numbers, it would still be a bust. I know most of you, if not all, realize this. But therein lies the rub, even if we do have a bust, those factors likely do produce some majors that track into the Caribbean. We don't have the same setup as 2010 and 2011. We're going to see some strong long-tracking hurricane impacts in 2020. Edit: Err.. 2011, not 2013. lol... That an entirely different scenario. Just, no. Also, I keep adding on and on to this post, sorry, however, I also want to point out that[mention=1541]Scorpion[/mention] never said anything about a bust. They were referring to hyperactive seasons with no major hurricane impacts. I just brought up the bust discussion because it seems to be floating around already in this thread and I was already rambling besides.
