Ground Scouring

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Everything posted by Ground Scouring

  1. Based on improved methodologies since then, reanalysis will likely lower Allen's peak about 10 kt or so. The upcoming third pass will likely show Patricia tied with or lower than Wilma. I hope that the crew is getting images, considering the nice moon tonight and intense eyewall lightning...
  2. And all these observations are from the "weaker" southeast quadrant, amazingly. Winds are likely 165-170 kt, based on the higher reduction ratio likely applicable in this RI case.
  3. I never said that it wouldn't be devastating...a larger, 130- to 135-kt hit is extremely destructive. A little more polite tone would be nice, too.
  4. Given everything that I've mentioned, plus the fact that previous NHC forecasts (such as at 03Z) showed ~20 kt of weakening due to shear, I'm surprised that the latest forecast totally omits shear/land and shows no weakening before landfall, despite mentioning ERC potential. Why?
  5. The landfall intensity is unlikely to verify as microwave data indicate a formative outer eyewall that is likely to commence an ERC over the next six hours. Combined with increasing shear and frictional effects from mountains, this factor is likely to cause faster-than-indicated weakening before landfall, regardless of exact speed and track. (Keep in mind that the NHC usually underestimates weakening as well as rapid deepening.) I would anticipate 130-135 kt (rather than 160 kt) at landfall, however, with an expanding wind field/fetch meaning a bigger storm surge.
  6. Residents in some of the islands were really caught off guard by Joaquin. I can see why. The southern islands (Acklins, Crooked, Mayaguana, and the Inaguas) were not even under a Hurricane WATCH until 5:00 a.m. EDT/09Z this morning, only four hours or so before hurricane-force winds arrived, because the NHC track failed to account for the more southerly movement and showed an earlier westerly turn, keeping hurricane-force winds north of those islands. Why didn't the NHC at least recommend a watch? This reminds me of Humberto 2007, when a rapidly intensifying storm deviated east of the forecast track and was expected to be near hurricane intensity, yet the NHC, following earlier model guidance and intermediate advisory protocol, showed an earlier landfall in Texas and didn't even recommend/issue a Hurricane Watch. The reliance on continuity really seems dangerous when dealing with an evolving situation so close to land. Will this be fixed? While I hate to blame the NHC, in this and some other cases, I don't see how it can avoid responsibility for failing to recommend appropriate watches/warnings because it adhered to continuity and model guidance instead of short-term meteorological trends. Are Bahamians suddenly even less important because they aren't U.S. citizens? (Note: I actually posted the above on the NHC's Facebook page and am eager to hear its response.)
  7. Pine Cay in the Turks and Caicos Islands has been reporting sustained, low-end TS winds of ~35-40 kt for several hours overnight and currently. I don't know the elevation of the anemometer, but the Turks and Caicos are not under any TS Watches or Warnings.
  8. The 06Z GFS ensemble mean shows a significant eastward shift, keeping Joaquin east of the U.S. and out to sea...it's a bit early, but I'm thinking that this will end up as a significant synoptic-scale victory for the ECMWF suite. The first visible images show that the eye is practically right over Samana Cay. San Salvador Island, some ~80 mi to the northwest, earlier reported sustained winds of 74 kt with gusts to 96 kt...very impressive, considering the distance. With dry air now fully mixed out and a solid, persistent ring of cold cloud tops enclosing the eye, I expect significant strengthening once the eye clears out later today. Probably 125-130 kt (perhaps 135 kt) is reasonable. Edit: Thanks to billgwx for the correction.
  9. If Joaquin were, by virtue of its large size, be able to phase more fully with the cutoff low via binary interaction, then I see no reason why it might not be a low-end major hurricane (~100 kt) at landfall if it were to track into eastern NC. SST anomalies off the Southeast coast have been running several degrees above average this summer and very high oceanic heat content has been concentrated in the Gulf Stream. As Joaquin accelerates north, its faster movement should offset the effects of increasing shear somewhat. Plus, we will likely be dealing with a moderate to strong Category 4 hurricane over the northeastern Bahamas (120-125 kt), based on current intensification trends and the favorable outflow pattern that is to develop in a day and a half or two. That means an even more intense system to deal with as it interacts with the cutoff. Someone on Twitter brought up a good point: that the ECMWF ensembles, while showing a very intense Joaquin, taking it out to sea show a smaller system (as does the deterministic run) than is actually the case. While the southwesterly movement and deeper intensity would favor, relative to the trough axis, a sharper northeast curve, the larger size of Joaquin might well compensate and allow more interaction with the trough. Honestly, I just don't see how ex-Ida will affect the track of Joaquin. The main factors will be location/intensity in one and a half to two days, how fast the cutoff moves/develops, and how large of a system Joaquin becomes. Based on the overall size of the system, I am becoming a bit more concerned that the ECMWF ensembles may bust, contrary to my original expectations, though I still am unwilling to change my bets.
  10. The collapse of convection over the western semicircle since ~12Z clearly shows the influence of drier low- to mid-level air wrapping around from the north. So long as the dry air is in place, hindering the further development of the inner core, then the intensification we have seen thus far is likely to level off. The system will probably need another day to fully mix out the dry air, by which time the low-level ridging to its southwest should start to weaken. That weakening trend should allow the formation of a deeper moist inflow from the Caribbean and cut off some of the dry air infiltrating from the north. Once the dry air diminishes, I fully expect rapid intensification, given what we've already seen under less-than-ideal conditions.
  11. Comparison between the 00Z and 12Z ECMWF ensembles shows more spread among the individual members and less of a phase within the 12Z guidance. The 12Z suite also shows less of a sharp northwest bend with many members, with more showing a general north movement off the East Coast than at 00Z. So there is a definite eastward trend within the widening spread/uncertainty, further supporting my contention that a more southerly/deeper storm within the short term would more likely miss the East Coast.
  12. The convective pattern of Joaquin suggests that the center may begin moving almost due south or west-southwest over the next 12 hours. The developing inflow band on the south and west sides will likely pull the center southward as convection strengthens, further enabling steady intensification. Rapid deepening will likely begin in earnest late tomorrow as the internal structure improves. I'm thinking that 90-95 kt by late Thursday seems very plausible, and I would not rule out 100-105 kt. A significant impact to San Salvador and Eleuthera is increasingly likely.
  13. I think that the models have yet to come to terms with the short-term movement of Joaquin. The GFS has been much less reliable than the ECMWF ensembles in gauging the more southwesterly movement of Joaquin over the past 24 hours. The GFS was inconsistent and, until the past run, showed no sustained south-of-west motion before the turn to the north. Conversely, the ECMWF ensemble mean has shown this for more than a day, and has a done a better job with Joaquin's stronger-than-anticipated status. This has key implications for the long-term track of Joaquin, for its position in two to three days will affect how it interacts with the cutoff low over the Southeast. The ECMWF ensemble mean is almost ~2 degrees south of the GFS solution by 12Z Thursday. A deeper and more southerly Joaquin, as seems more plausible, would more likely turn sharply northeast and miss a potential phasing with the trough as it acquires a negative tilt by days four and five. Being near the trough axis rather than upstream, Joaquin would not turn significantly west of north by day five. A well-known meteorologist on Twitter likened the scenario to a person (the trough axis) kicking a football (Joaquin). By 120 hours, the blocking heights to its northeast will start to flatten, allowing the cyclone to curve just offshore of the Mid-Atlantic and southern New England. This scenario seems more likely than a Sandy-like phase over the Mid-Atlantic. Needless to say, I'm far from being sold the deterministic GFS solution, especially since a hurricane striking the Mid-Atlantic or New England in a strong El Niño year would be unprecedented.
  14. Josh should seriously consider flying to Nassau and then to the outer islands for this one... Latest recon data suggest that winds are likely 55-60 kt. Edit: ATCF has 55 kt for the 18Z fix.
  15. Once the low-level and mid-level centers become fully aligned, I truly believe that Joaquin will likely intensify faster than forecast. By days two and three, the storm will be wedged between a developing cutoff low over the Southeast and a cold mid-level trough over ex-Ida to its east. Such an environment is not only conditionally unstable, favoring rapid convective growth, but also, with a blocking high to the north, conducive to low ambient pressures as well as upper-level divergence. This environment, filled with ample low-level moisture and high precipitable water, would support the development of dual outflow channels in the south and north quadrants of Joaquin, especially as the cutoff low becomes negatively tilted by day four and beyond. As Joaquin interacts with the trough, it may maintain its intensity or deepen even further on day four, thanks to some indirect baroclinic influences, as the storm initially parallels the mean shear vector. Already, Joaquin is clearly organizing even though the centers are not yet fully aligned. The storm is clearly intensifying faster than originally expected, and even the deterministic ECMWF is likely underestimating the rate of deepening, showing 990 mb by 12Z tomorrow, even though the pressure is already down to that level. An excellent outflow channel is already established in the southern quadrant, and the nascent CDO is slowly expanding westward as northerly shear lessens. Based on all indications, significant, quite possibly rapid intensification will commence tomorrow, as an upper-level anticyclone builds over the system. Thus, Joaquin will likely have about four full days (Wednesday through Saturday) to intensify significantly. The stronger intensity in the short term would likely bring the cyclone into the east-central Bahamas in little more than two days, with the deeper system enhancing mid-level heights to its north. The ECMWF ensembles have consistently shown this. Given all indications and trends, I would not be surprised if Joaquin becomes a significant hurricane (85+ kt) as it meanders over the east-central Bahamas on Thursday and Friday. A potentially severe impact to the Bahamas (Eleuthera, Cat Island, San Salvador, and possibly even the Exumas) is becoming more plausible. The 1929 Bahamas hurricane underwent rapid deepening in a similar set-up; Joaquin may well follow its example, only farther east.
  16. Even with the MJO inducing upper-level divergence over the western Caribbean in a week, the strong vertical shear lurking just to the north would kill anything tracking out of the Caribbean. Plus, there's land interaction to contend with. I'm leaning toward no development.
  17. I really feel that the NHC is too nonchalant about how its forecasts are communicated. In the NHC’s view, consumers, media, and government are responsible for their own behavior. While technically true, taking such a hands-off approach and making incremental, relatively modest changes to the forecast products seems an underwhelming response to a significant problem. The NHC should cater to consumers, not vice versa. Additionally, the media and governments should be held accountable for their own incompetence and/or misinformation. If I were the NHC, I would set up a group of specialists with broad interdisciplinary experience, including in behavioral psychology, communication, and maybe even neurology. This group, located within the NHC but separate from forecasting duties, would aggressively use social media and other levers of communication and direct how the media and government communicate official forecasts to the public. The group would call out, correct, and advise media and government on how to present official forecast products. I would also make significant changes to the products themselves. Personally, I have long inveighed against having the five-day cone as a publicly visible product. Although five-day errors, both with the track and intensity, have diminished in recent years, uncertainty is quite high even two or three days out, especially with weaker systems like Erika. I think that the NHC should continue to use the five-day cone as an experimental product, but use the three-day cone as its sole public product. Prepared residents and competent officials need only a few days to get ready. On the NHC site, the first product that viewers should see is not the three-day cone, but the various wind probabilities charts (34-, 50-, and 64-kt), which should only extend out to day three. Maybe the probabilities legend should also be modified so that only the ≥ 50% (high probability) areas are highlighted. Viewers would then have a higher degree of confidence in the forecast and have a better idea as to what impacts could be expected. More specific, area-relevant rainfall, wind, tide, and other impacts could then be given out with greater certainty. (In addition to the main probabilities charts, I might also consider adding a separate but analogous product for major hurricane winds in severe storms.) Finally, I think that Erika and other storms have shown that the global models, while not perfect, have improved sufficiently as to be preferred over the statistical and other dynamical guidance in many cases. The ECMWF ensembles and ensemble mean have proven, time after time, to be the most reliable track and intensity guidance, overall, within 72 hours. To use this season as an example, they did a better job with Danny, Erika, and Grace than any of the other global models (including even the ECMWF deterministic run!) and had fewer phantom storms for cyclone genesis. Had the NHC given greater weight to these global models with Erika, its track and intensity forecasts would have likely been much more accurate, if not perfect.
  18. 3-5" of rain and minor street flooding over three days do not represent an extreme rain event outside saturated areas. Maybe the lack of strong landfalls makes people exaggerate anything that nears land. The really extreme rainfall occurred over Dominica and Hispaniola, with unfortunate, deadly results...
  19. To be honest, I don't see how this will be a significant precipitation event for the FL peninsula. The vorticity will likely fall apart as it moves west-northwest over Cuba and into the southern Gulf before being sheared by the mid-trough. Without a well-defined system, however weak, in the area, the threat for widespread heavy rains drops considerably. HPC's three-day QPF outputs have gone down from 5-8"+ yesterday to 3-5" today, with most of the heaviest totals affecting the southern and western coasts of the peninsula, with a sharp gradient heading inland. If you live in an area that isn't already saturated, such modest three-day totals won't produce anything more than some minor, localized flooding. I feel that the threat has been broad-brushed, giving most residents outside flood zones a false sense of severity.
  20. Erika is likely making a little comeback off the north coast of Cuba. Convection is increasing over the remnant low-level vortex and the system is quickly moving into an area of somewhat lighter vertical shear, near the axis of the developing anticyclone over the Straits of Florida. I think that we'll likely see Erika regenerate into a weak TS (35-40 kt) sometime overnight or early tomorrow, necessitating TS Warnings for the lower Keys and the west coast of Florida. A regenerating Erika would likely track a bit closer to the Tampa Bay area once it makes its turn more to the northwest after passing near the lower Keys. A stronger-than-expected Erika slowing down or stalling near the Big Bend would likely result in greater QPF output than either the GFS or the ECMWF indicates, thanks to training bands. The potential for significant flooding over parts of the western and northern FL peninsula would exist.
  21. CIMSS analysis indicates that the mid-level circulation is heading fairly close to 305° over a valley northeast of Port-au-Prince. That is pretty close to, or even just north of, the NHC track. On its current heading it may reach the Windward Passage and, once over water, could put down a low-level center near the easternmost tip of Cuba. Observations from Port-au-Prince indicate that some low-level feature could already be attempting to form closer to the mid-level vortex. Vertical shear will be reduced and is already likely decreasing thanks to the strong convection inducing warming of the atmosphere, thereby weakening the upper low to the northwest of Erika. All these trends, if sustained, could suggest a stronger system (45-50 kt perhaps) nearing FL a bit farther east, close to the upper Keys and the westernmost Everglades. I'm not sure, so I think we need to wait and observe trends. Personally, I would give turtlehurricane's scenario at least a bit more likelihood, maybe 30-35% of occurrence.
  22. How well would the mid-level vorticity survive its passage over Hispaniola? The 12Z GFS kills the vorticity over land, resulting in an open trough moving into South FL.
  23. The latest NHC discussion notes: Do you think that, if that were to occur thanks to the destruction of the remnant surface center, the NHC forecast for a strong TS in FL (the 72-hour position is 50 kt inland, indicating 55-60 kt at the coast) could verify?
  24. The NHC is forecasting a strong tropical storm (55-60 kt) at landfall in FL, given that the 72-hour position is 50 kt well inland. This is a 100% bust on the high side.