Shell Mound wrote:Kingarabian wrote:NDG wrote::uarrow: Any hurricane threats to Hawaii over the next couple of weeks will have to track westward south of the 15th Latitude before approaching the Islands, SSTs are still a little too cool east of the 150th longitude and north of 15th lat to support a Hurricane. IMO.
East of Hawaii they're about 25C which would maintain a storm with hurricane strength.
But there cant be much shear. Around late July through ASO they warm further. I don't remember a potential Hawaii threat this early in the season in recent years. I don't think 2014/2015 had any until late July or August.
If anything, while the CPAC has warmed considerably over the past decade, vertical wind shear near Hawaii seems to have
increased. Of the few hurricanes known to have directly impacted the Hawaiian Islands, all occurred in or prior to the early 1990s, with the most recent hit being Iniki in 1992. All impacts since then have been tropical storms at worst. Perhaps the same climatic factors that are driving the increase in CPAC activity are also strengthening the "shield of shear" over the Hawaiian Islands. So perhaps we shouldn't automatically conclude that the risk to Hawaii, especially in regard to hurricane impacts, will be higher than in previous decades, since the increase in shear seems to be offsetting the overall increase in activity to the south and east of the islands.
I respectfully disagree. As I stated in the CPAC thread earlier in the month, there are 3 factors that have generally kept Hawaii safe from TC landfalls. SSTs, shear, and steering:
But since 2014, SST's in the vicinity of the main Hawaiian islands have been anomalously warm to the point where we're seeing a lot of major hurricanes maintain their strength very close to the islands. Fortunately when the ridge allows for a track that would allow a system to make landfall over any of the islands, shear is strong, and when shear is low, the STR is holding firm and does not allow for a track towards the islands.
Your argument here is that although SST's have increased, shear has also increased. While it's true there's a persistent belt of high shear situated close to the main Hawaiian Islands, it's not what kept Hawaii safe from a bunch of threats since 2014. It was mainly the steering patter not allowing for storms to reach Hawaii.
Below is a list that of systems that were hurricanes( or prior hurricanes), and had Hawaii as a target either from a CPHC forecast track or a bunch of computer model runs. This is all documented in the archives. I'm not including tropical storms.
I will highlight the systems that were weakened by shear with the color BLUE and the systems that were steered away either from a trough or the ridge holding firm with the color orange.
2014 Iselle was weakened by shear but not nough to stop it from making landfall over the BIg Island and causing nearly 150M in damage.2014 Julio remained a Cat 2 as it tracked 200-300 miles north of Hawaii due to a weakness in the ridge.2014 Ana was taking an Iniki type track and would've hit Kauai or Oahu as a Cat.1 hurricane had the ridge not amplified and forced it west and away from Hawaii.2015 Guillermo was a combination of steering and high shear that kept Hawaii safe from the system.2015 Hilda shear saved Hawaii on this one.2015 Ignacio similar path to 2014 Julio, sub tropical ridge weakening took it away from Hawaii.2015 Jimena, Hawaii was kept safe due to a combination of cooler SSTs and a weak ridge.2015 Otto, steering wasn't there.2016 Darby was weakened due to cooler waters not shear. If waters were warmer, the steering pattern would've allowed a double hit on Hawaii, one on the south end of the Big Island and another on Kauai or Oahu.
2016 Lester, Hawaii was safe due to a similar weakening of the ridge that occured with 2014 Juilo and 2015 Ignacio.2016 Madeline, the Big Island was saved by shear.2018 Hector, it was not shear that kept Hawaii safe from this beast. It was the ridge holding very firm.2018 Lane, shear saved the day2018 Miriam, steering pattern wasn't there2018 Norman, similar steering situation 2014 Julio, 2015 Ignacio, and 2016 Lester. 2018 Olivia, shear significantly weakened the system before it made landfall2018 Walaka thankfully didn't recurve until it cleared the islands.Note that I may have missed something on a couple of systems on why that particular system did not affect Hawaii but all these systems listed above at one point were realistically considered to hit Hawaii. You can visit their respective threads in the archives if you want to.
But It's CLEAR that since 2014, steering and timing played a much more significant role in keeping Hawaii safe than shear. This is also alluded to that warmer SST's help lower shear which has been the case since 2014.
Lets face it, Hawaii is essentially safe from tropical cyclones approaching from the east with a few minor exceptions like Iselle in 2014. You’ll have to have an approaching tropical cyclone from the south or southwest in order to get a really significant tropical cyclone impact a lot like Iniki and even those are VERY rare to come by as most tropical cyclones that go into the Central Pacific region form in the East Pacific not in the Central Pacific like Iniki.
