Windspeed
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Everything posted by Windspeed
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Looks like a depression to me. Especially with that ASCAT pass last night confirming the closed low. All it needed was sustained convection and a bit more organization. Interesting how even a quiet stretch with most meh environmental conditions can still produce surprises. But 99L is an especially strong wave born out of a favorable environmental bubble thanks to the WAM and ITCZ boundary. Looks like if things continue, we'll get a NS. Questions remain if it can become anything substantial in the long term / Caribbean. It still has to deal with a lot of unfavorable possibilities.
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Well then...
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Considering that ASCAT pass, if we get any sustainable convection over that center, we'll probably get a classification. Clearly there is a closed low. Perhaps it doesn't survive the potential hostile environment in a few days, but it may still get named. Interestingly, this feature might spell trouble with the Western Caribbean next week. The favorable coupled Kelvin may be timing just right off to extend east off of Central America by then.
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New paper by NOAA/OAR/AOML on the relationship between the Madden-Julian oscillation (MJO) and rapid intensification of tropical cyclones. Important Conclusions: 1. Rapid intensification events and the MJO tend to move with each other from west to east across the hemisphere suggesting a relationship between the two. 2. Rapid intensification is most likely to occur when the MJO is neither stormy and wet nor sunny and dry near the tropical cyclone. 3. The addition of information about the MJO does not improve forecasts of rapid intensification. This is likely because the information about the MJO is already available in the forecast models in a different form. Klotzbach (2012), in their seminal study on the relationship between RI in the Atlantic and the MJO, found that RI is four times more likely during the active MJO phase than during the inactive phase. The current study extends this work to the Central and East Pacific and tests whether the MJO may have predictive capability in current forecast schemes. All RI events in the north/western hemisphere along with the two commensurate RMM modes (Wheeler and Hendon 2014) are compiled from 1974 to 2015. The events are compiled into 20-degree-wide bins, and the mean values in each bin show that RI events and MJO events tend to move in tandem with each other from west to east across the hemisphere. Unlike in the Klotzbach (2012) study, the MJO is not generally in the most active convective phase in the region when RI occurs. Though the mean magnitudes are small, the differences between many bins are statistically significant. However, the addition of this information to statistical RI forecasting schemes does not significantly improve forecasts from SHIPS-RII, possibly because the MJO is not related to RI itself, but instead to cyclogenesis, a necessary precursor to RI, or due to the large scatter in the RMM values. Though the results here show a relationship between the MJO and RI events in the hemisphere, they do not show improvements to current operational RI-prediction models. Despite this, other techniques, such as those based upon machine learning or other artificial intelligence algorithms, might be useful to pursue in the future. Paper can be obtained here. Some additional thoughts of my own. Though clearly a favorable MJO or strong coupled Kelvin can help induce tropical cyclone genesis via an existing MCS, disturbace, wave, etc., there is clearly other factors at play with respect to an existing strong convectively coupled Kelvin and an already established TC going through RI. It may even be possible that a strong coupled Kelvin could create too much surrounding convection and competing micro regions of convergence that might limit low-level feed or interfere with the main vortex of an established TC. Also, since this paper focused on how currently existing RI models do not seem to benefit from additional MJO- Kelvin data, though an unfavorable MJO phase might deter RI, a favorable coupled-Kelvin doesn't necessarily increase existing parameters for RI of a potential TC. Essentially, though a convectively-coupled 200 hPa vorticity wave does greatly establish much better support of TCGs, it does not necessarily help in their RI phase if already mature, and that a neutral phase of the MJO might be the most conducive for RI of an existing TCG.- 46 replies
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AL90 in the NW GOM looks too sheared over the potential weak circulation due to strong southeasterly flow. It's not got a lot of time remaining over water.
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Hrmm...
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RE: A potential switch is currently crossing the central into EPAC. A very intense convectively coupled Kelvin wave. This will be making its way over the Atlantic Basin in the 10-14~ day range. Surprisingly there are no signs of blossoming activity in mid-to-long range modeling yet, but that could easily change. Something to keep an eye on..
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Meh...
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It came off the lower 48 on a SSE track off the coast. Yes, you're correct, the feature is not moving SSE now. More S to SSW on a long bend into the southern periphery of building heights to the NW. It also needs to pulse up new convection relatively soon or the possibility of generating a LLC vort max will fade. The MCV may very well dissipate. At any rate, it was worth the mention. We've seen these little systems develop often enough after rolling off the lower 48 and SE.
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An MCS moved SSE off of the ETX/LA coast into the NW GOM. It does have a weak MLC. This feature will turn SW, WSW and then W into the Central or Southern Texas coastline in about 36-48 hrs. So not a lot of time to develop; that being said, if convection persists and a low level vort can develop, there is potential for a TC to form prior to landfall. The upper pattern is favorable enough. At least something to keep an eye on...
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Current Atlantic oceanic heat potential compared to 2017, the last hyperactive season on record. Obviously heat potential and depth of 26ºC isotherm is only part of the equation. You need an anomalously favorable atmosphere and steering pattern. That being said, if the atmosphere over the Atlantic Basin does become more favorable in the coming weeks, the basin does look primed. July, 17th, 2017: Current: Now the question remains what atmospheric patterns will be in place for the last half of the Atlantic Hurricane season? 2017 had a relatively neutral ENSO but a positive AMO. NAO trended positive and IOD trended negative by September when all hell broke lose. Interestingly, a similar scenario may be unfolding by then but with an actual negative ENSO in place. We do not have a full blown negative ENSO yet, but it is trending that way.
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Vertical profiles for most of the Caribbean and MDR are on point right now for TC support, however, SAL in the mid-to-lower levels and sinking air is keeping things quiet in the short-term. This is an ominous sign for when more favorable 200 mb support and 900 to 500 hPa lift begins to creep in by August however. I do expect things to go active and ramp up in a hurry when they do.
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Late July into the first week of August just might be the kickoff. Signs of a favorable MJO coming into play. Easterly winds will dominate the tropical Pacific region, reinforcing La Niña; at the same time, due to a robust standing wave over the Western Indian Ocean and East African highlands, convection should continue to propagate westward with persistent wave breaking, which will feed tropical waves into Eastern Atlantic and MDR:
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JMA on board for an active Aug-Oct throughout the Atlantic Basin and MDR.
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The proverbial calm before the storm?...
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The naming of Winter storms has always been controversial due to unwarranted exemplification of ETs/mid-latitudinal storms, their frequency of occurrence, and hype that overwhelmingly isn't required from a human impact and safety standpoint. The naming of Tropical Cyclones, on the other hand, is entirely warranted due to those same phenomenon. We name them because they can be inherently dangerous. Sure, some are just a maritime nuisance. Also, sure, with better RS technology, better satellite resolutions and data gathering, we classify TCs that likely wouldn't even get noticed several decades ago. But sticking to the rules of what gets classified, it would be silly to keep them unclassified merely because they are weak, less substantial/impactful events, or even subtropical. We name TCs for important reasons, hard to argue against that. But we also need to stick to the rules. If a system meets the criteria, it gets classified, period. I realize the tongue-in-cheek on the off-topic here. But it's worth reminding and pointing out why NOAA/NHC handles TC classifications the way they do, and also why private companies naming mid-latitudal ETs is ridiculous and of little credence beyond attention generation and money for their service platforms. It's hardly a matter of public safety and science. Major differences in mission strategy and purpose here.
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Another healthy wave south of the Verdes. Easterlies are still a bit lopsided towards the 700 hPa level. But the wave train continues. Eventually easterly trades are going to better align as Azores ridging takes its seasonal build/shift westward into an ECONUS WAR/SER; we already have ENS support for strong interior CONUS 600 dm heights incoming; and if these waves continue training, ITCZ wave breaking and an axii is inevitably going to close off at the surface and stack. The vigor in the WAM and ITCZ needs to be paid attention. We are mere weeks away from modeled increasing MDR favoribility. If that happens sooner, expect one of these waves to develop into our first MDR TC before August.
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Good thread on current anomalous upper tropospheric temperature profiles that may persist into the heart of the Atlantic hurricane season. Generally, cooler upper profiles aid in colder cloudtops and more intense convection. May also aid in upper divergence for 400-200 hPa anti-cyclones.
