Windspeed
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Everything posted by Windspeed
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Seriously, if something significant does advance west out if the MDR, that has ECONUS landfall written all over it.
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That pattern tho..
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It's actually performed better at TCG than the current operational. Yes, every once in a while a storm will form in the mid-range due to a feature in the pattern change. However, the current operationals are missing the mark too frequently on near-term TCG potential. Like 99L for example. The current para is the only one that has a TC. Perhaps that fails to occur and it misses the mark. But the operationals have chosen poorly with genesis environmental fields. We shall see.
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I left off the '1'. Spring 2021 is tentative for upgrade if there are no issues.
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Incorrect. That is the non-operational parallel GFS model that would become the GFS version 16 operational in 2021 if there are no hitches. It is still in experimental phase. The current operational GFS is version 15.
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99L in the eastern Caribbean is looking really healthy today. It is convectively active along the axis with notable southerly backside flow in the low levels. This probably does not yet have a closed circulation at the surface, but the cloud pattern is suggestive for mid level cyclonic turning. There is a building upper 200 hPa anticyclone over the Caribbean and sufficient easterly 800 hPa moisture surge surrounding 99L's envelope. Shear is nil through its potential westward track. If the disturbance manages to close off a surface vortex, it has the ingredients to intensify.
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It's absolutely possible but a rarer solution. You need a very strong NS/NF/Greenland maritime block and general troughness N. Plains and Central Canada. Takes a lot of luck (or bad luck depending on perspective) to get that setup and a TC in the right position, but it does occur. Anyone remember Hazel? Again, not saying this is going to happen, but SSTs off the SE are still way above normal. Isaias did little to upwell and the disturbance forecast to move ENE out into the Atlantic won't be strong enough to put much of a dent in the thermocline. Also similar setups have been Hugo and Isabel, though Isabel was a large mess by the time it got up to the Carolinas. You also need a favorable upper environment and mitigatable shear, which is also more difficult at that latitude. So it takes more than just the maritime block. But we can get NW moving systems off the SE to Outer banks and have them reach the Great Lakes region.
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We've got an orange and two lemons now. ZCZC MIATWOAT ALL TTAA00 KNHC DDHHMM Tropical Weather Outlook NWS National Hurricane Center Miami FL 200 PM EDT Sat Aug 29 2020 For the North Atlantic...Caribbean Sea and the Gulf of Mexico: 1. A tropical wave located about 550 miles east of the Windward Islands is producing disorganized showers and thunderstorms. Some gradual development of this system is possible during the next several days while it moves westward at about 15 mph toward the Lesser Antilles. Regardless of development, this system will likely produce gusty winds and locally heavy rainfall across portions of the Windward and Leeward Islands on Sunday. * Formation chance through 48 hours...low...20 percent. * Formation chance through 5 days...low...30 percent. 2. Another tropical wave is located over the eastern Atlantic Ocean just southwest of the Cabo Verde Islands. This system is expected to move very slowly for the next several days, and some development is possible early next week over the eastern or central tropical Atlantic. * Formation chance through 48 hours...low...near 0 percent. * Formation chance through 5 days...medium...40 percent. 3. A low pressure area is expected to form off of the southeastern coast of the United States early next week. Additional subsequent development is possible as the system moves east-northeastward across the northwestern Atlantic Ocean. * Formation chance through 48 hours...low...near 0 percent. * Formation chance through 5 days...low...20 percent. Forecaster Beven
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The only metric that seems off from seasonal forecasts at this point is accumulated cyclone energy (ACE). Though we're above normal, considering number of storms, an ACE of 42.1 seems low. However, bulk ACE generation is almost always in the months of September and more recently October when we experience a higher number of concurrent hurricanes. September hurricanes generally take tracks that allow them to last longer too, hence higher rate of ACE production.
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13 named storms, 4 hurricanes, 1 major hurricane by August 26th...
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The para is interesting in that it is building heights across the northern maritimes into a Canadian block by Sept 5th. That is a classic long-tracker pattern that typically results in repeating WATL landfalls. Also develops an Azores cutoff that breaks down 700 hPa flow off NW Africa and the MDR moistens with precipitable water substantially as we approach peak. This will have to be watched for pattern trends in coming runs as that would suggest a busy September.
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The big three globals have been struggling with TCG since Dorian. No idea. A lack of data or some other nonsense. It is a known issue.
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If ever there was a case in point, this is it. 5+ days out you might peek at the operationals for patterns, precip, derived winds, feature locations, and especially entertainment purposes, but for estimates on TCs and their storm relative potential, you go with the different ensemble packages all night and day long. I don't mind beating that dead horse into a smear until frequent posters get it.
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Possible Atlantic MDR development next week being modeled in several ensemble camps.
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Good lord that AEW went poof!
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Well it is a large wave with a noticeable mid-level circulation. It appears to have exited slightly more north and will pass through the Cabo Verdes. It also has a very nice mid-level moisture envelope around it. Obviously there is very stable dry air, but well NW of the wave itself. SSTs at that latitude are marginal but as it keeps gaining longitude, they do increase to support genesis. We'll just have to keep an eye on it. It is color-coded orange by the NHC with 40% probs in the 5-day outlook.
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What the hell is going on with the GFS lately? Sheesh...
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There it is, Chief... Jokes aside, that is the most impressive sub-Saharan MCS I have seen since Irma. This is going to be fun to track regardless of pattern shenanigans. Granted, Florence's was nice too, but not that intense.
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We've been in an unfavorable phase, but favorable upper 200 hPa vorticity is now spreading over the Atlantic Basin and should have a negative mean through the end of August. Afterwards, a rather neutral phase will persist over the western basin with stronger vorticity remaining over the far EATL/WAM. At any rate, you don't need a strong MJO, you just don't want to see a suppressive regime dominating the entire basin. Upper divergence should persist over the WAM through peak season to keep strong AEWs exiting the African continent.
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Mentioning this here as it relates to an overall pattern feature. The MJO is currently increasing favorability across the Atlantic Basin as was forecasted. This should remain in place for the next few weeks, perhaps longer. Interestingly, one of the side effects of robust upper 200 hPa vorticity can be a negative when associated with a monsoonal trough. That's exactly what we have going on in the EATL right now. The WAM extension west into the MDR with two competing wave axii and strong low-level convergence amplified by the ITCZ. This is otherwise generally great for TCG; however, if you have multiple regions of vorticity within close proximity and robust convection occurring over a large area, it can sometimes take an extended period of time for one of the competing regions of vorticity to become dominate. If these regions were further apart, you'd likely get two TCs develop. A favorable MJO phase is always better for TCG than a an unfavorable phase. But there can still be caveats. There has also been research done on how a positive MJO phase influences rapid intensification. Interestingly, it was determined that though the MJO greatly enhances convection to allow for TCG, it doesn't necessarily help with rapid intensification of a particular cyclone. Again, competing convection may have something to do with this as the internal convection within the TC's vortex structure may have to compete with surrounding areas of convection. Sometimes that can be a negative factor, though perhaps not as much if the vortex is already intense. We saw this occur with Major Hurricane Matthew in the deep Caribbean back in 2015. It became a Category 5 despite having to compete with backside intense MCS complexes with competing MLCs rotating outside its main vortex. Though there is a need for more research to be done, I suspect the best scenario for TCG would be an isolated wave convectively influenced by a favorable MJO phase, but not one so strong that it over-amplifies surrounding regions of convection, which may induce subsidence on the resulting TC. Obviously when dealing with a monsoonal trough with multiple wave axii, the possibility of slower tropical development may be a real thing. Though that tends to work itself out when one of the low-level vortices eventually becomes dominate. We'll see how this evolves with 98L. In the meantime, 97L may benefit from the phase much more favorably for TCG in the next 24-36 hrs, as it is certainly isolated, and will position itself in a region of the Caribbean for improved low-level convergence as low-level wind profiles becomes more favorable. Upper divergence isn't an issue. There is some dry air, but the overall upper pattern is favorable.
