Rasvar
Weather Master
Reged: Fri
Posts: 571
Loc: Tallahassee, Fl
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Quote:
The 8pm advisory states that Hannah is drifting EAST, is this a typo or is she actually moving EAST?? Confirmation appreciated. An eastbound hurricane is a new one for me. 
It is not all that uncommon. Many storms do loops. It does seem much more likely that the storm would loop from SE to E to NE to N to NW at this point since it has been generally moving in that type of circular motion.
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Jim
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vineyardsaker
Weather Guru
Reged: Wed
Posts: 150
Loc: New Smyrna Beach, FL
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Can two tropical cyclones, say two hurricanes, actually collide and, if yes, what happens when they do?
Thanks!
VS
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Charley(eyewall), Ivan, Jeanne, Dennis, Wilma, Irma, Ian (eyewall), Nicole
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Lee-Delray
Weather Master
Reged: Thu
Posts: 429
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Two hurricanes can collide its called the Fuijiwara Effect, Wikipedia states:
When the cyclones approach each other, their centers will begin orbiting cyclonically about a point between the two systems. The two vortices will be attracted to each other, and eventually spiral into the center point and merge. When the two vortices are of unequal size, the larger vortex will tend to dominate the interaction, and the smaller vortex will orbit around it.
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Myles
Weather Hobbyist
Reged: Wed
Posts: 80
Loc: SW FL
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When hurricanes get close enough to each other they do spin around each other in the Fujiwara effect, as Lee-Delray said, however, they can begin interacting even before that. The outflow from the systems will disrupt each other, acting as shear. And if they get close enough(very, very close) the two circulations can disrupt the inflow to each other as well. Generally both storms weaken when they get too close.
In the case of Hanna vs Ike...Hanna has very establish outflow to the east an south, extending many hundreds of miles away from the center, Ike, while having a better overall structure, doesn't have near the outflow to the west of the center to combat Hanna's large envelope of outflow extending past the Leeward Islands. It would seem likely that Ike would come out worse in this scenario, but it wouldn't be good for either storm.
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lunkerhunter
Storm Tracker
Reged: Fri
Posts: 248
Loc: Saint Augustine, FL
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looks like Kyle could be the biggest of the 4 siblings. take a look at the next wave leaving Africa. 
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Matthew '16, Hermine '16, Colin '16, Bonnie '10, Fay '08, Wilma, '05, Katrina '05, Jeanne '04, Frances '04, Charley '04 in FTM (drove behind it), Bertha '96, Bob '91, The Blizzard of '78 in NH
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RevUp
Weather Guru
Reged: Sun
Posts: 181
Loc:
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NHC has been doing an overall great job keeping up with these storms and incorporating an incredible amount of analysis and forecast data into their advisories.
Bottom line is that Hanna should be a hurricane in 24 hours and will likely inundate the northern Bahamas with squalls by Thursday before paralleling the FL east coast with high surf and landfalling along SC coast Friday.
By the time Ike enters this region on Sunday, he'll be encountering increased shear, just like Hanna has been, and seems to be destined for a WSW path across eastern Cuba, although the models are all suggesting slightly different variations at this point in time, as noted by .
I think it's been very interesting to see Hanna holding off and holding its own, until Gustav dissipates and merges with an approaching trof.
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"Let tomorrow worry about itself. Each day has enough trouble of its own."
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lunkerhunter
Storm Tracker
Reged: Fri
Posts: 248
Loc: Saint Augustine, FL
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but note that shear is forecast to weaken
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JonB
Registered User
Reged: Mon
Posts: 7
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Well..it all could change. Hannah does not look good. It will be interesting to see what it turns out to be.
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Survived:
Gloria '85, Bob '91, Irene '99, Francis & Jeanne '04, Wilma '05, Fay 08'
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scottsvb
Weather Master
Reged: Mon
Posts: 1184
Loc: fl
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I would send a PM to all the admins but Ill just want to know where is the IKE lounge. I see even Josephine, but am I just not seeing IKE? Anyways I posted up my forecast on Hanna in her lounge!
Edit -- it's there, it only has a couple of posts in it, though, and has sorta been bumped down the forum listing in the Forecast Lounge as a result. -Clark
Edited by Clark (Wed Sep 03 2008 02:46 AM)
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Clark
Meteorologist
Reged: Wed
Posts: 1710
Loc:
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The ultimate key for Ike is going to be how fast Hanna moves out. A continued slow movement for Hanna and Ike will catch up to the storm and will likely be directed northward in a bit of Fujiwhara-style interaction given its small size versus Hanna's large size. If Hanna starts to move northwestward soon, however, these effects are likely to be minimal. Look at the 00Z model guidance for further clues on this -- the slower Hanna moves, the more poleward Ike is directed. The UKMET model has been consistent with this for many runs now and the global models, all of which have pretty good representations of Hanna, suggest a slower movement than the /HWRF hurricane models and show a tad more interaction with Ike. What will happen? What happens today will be a big clue to that.
Overnight, Ike looks to be developing an eye and is nearing hurricane intensity; Josephine's deep convection has weakened and now the storm is caught between an upper level trough to its northwest and a very large tropical wave to its east. It's so far east, though, that even if it were to somehow make it across the ocean it is at least 10 days from the mainland. Hanna is still highly sheared but with such a large circulation envelope it's not going anywhere anytime soon unless it somehow manages to slide over Hispaniola. It should ultimately end up making landfall somewhere on the SE US coast, but as noted above it's still very much an open question as to explicitly when this occurs.
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Current Tropical Model Output Plots
(or view them on the main page for any active Atlantic storms!)
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Raymond
Weather Guru
Reged: Wed
Posts: 112
Loc: Germany
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I have another version:
Recon is in Hanna again and found a center near 20 N, 72.5 W with a pressure of 994 hPA. There is absolutely no stronger convection around it, as seen on microwave pics and there is nearly no rain around it a measured by recon. There are only small areas of winds with just tropical storm force around it and the flow pattern is a bit strange.
So I would say, this center will die down regardless where it moves in the next hours. Shear is also still quite stronge. The only weak chance for Hanna to survive I would see in a center reformation in the strongest convection much to the east. I hope recon goes into this area and looks, if there is something happening or not.
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cieldumort
Moderator
Reged: Mon
Posts: 2305
Loc: Austin, Tx
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Recall Saturday that Hanna very nearly was reclassified as a Subtropical Storm. The cyclone went from being a classic warm-cored tropical cyclone, to interacting with an upper-level low, and finally melding with the upper level low that day and night.
In response to interaction with the which had been impeding intensification, Hanna suddenly took on an appearance closely resembling that of a deep-layered, cold-core cut-off low. It is arguable that if it hadn't been for the northwesterly shear imparted upon it courtesy Gustav, Hanna would never have had so much very deep convection flaring up to the south and southeast... and subsequently, never had multiple center reformations to the southeast - and all would be good and well with forecasts insisting on an imminent northwesterly turn, but without those center reformations, Hanna could also have become a subtropical storm for at least a couple of advisories.
In the end, Hanna's LLC caught up with multiple rounds of extremely deep convection.. West Pac-style deep convection, even... and intensification was simply off to the races. But, as shear would have it, this was not to last.
And one now has to wonder how much that transition from tropical to (arguably) subtropical and back to tropical again really took.
The case for considering the possibility that Hanna is once again exhibiting a trend a bit back towards subtropical in nature is twofold:
First, a recent recon center fix, if correct, shows that Hanna may be attempting to turn into a cold-cored cyclone. By very definition, this would negate legitimately recognizing her as a Tropical Cyclone. Second, the strongest winds are no longer all right around the center of circulation, but also within a fuzzy band some 40-75 miles out from the center, based on the sampled portions of the windfield so far, suggesting some subtropical characteristics may be in play within the windfield. (This certainly isn't in well-developed rainbands in this region, as the rainbands are mostly all to her south and southeast (See Selected Recon Data Below)
The practical reason for considering Hanna partially still hanging on to subtropical traits is not merely in the interest of being correct, but such a consideration may actually have some implications for forecasting how the cyclone interacts with the environment around her. A subtropical cyclone might have more or less ability to withstand potential disruptions from land interactions, and in some cases, not react as detrimentally to shear, as two potentially relevant examples.
Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 3rd day of the month at 05:39Z
E. Location of the Estimated Maximum Surface Wind: 65 nautical miles (75 statute miles) to the NNW (330°) of center fix
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 16°C (61°F) at a pressure alt. of 1,525m (5,003ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 12°C (54°F) at a pressure alt. of 1,524m (5,000ft)
Hanna is now hugging the extreme north Haitian coast. Pressures are falling all around this island, and most of the deepest convection has persisted over and to the south and southeast of the island for over twelve hours, while the center of circulation has continued to pull ever more to the south and/or east, over all, over time.
A potential fly in the forecast reasoning is becoming apparent, as the ease with which this cyclone takes on a few significant subtropical characteristics when not burying itself within deep thunderstorms, such that its surface circulation remains very intact and symmetrical if only a bit morphed, and to then jump into wherever the deepest convection has reappeared - and to then transform back into a deepening, warm-cored tropical cyclone, opens up the distinct possibility that its surface circulation may begin to wrap around Haiti.. maybe gels somewhere even south or east of there... into the new location of deepest convection.
This bit of an outlier possibility should be reconciled by this time tomorrow. If Hanna has not by then begun the forecast northwest movement, something is probably amiss in that call.
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Rich B
British Meteorologist
Reged: Sat
Posts: 498
Loc: Gloucestershire, England, UK
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Satellite imagery shows Hanna is really very disorganised. Recon puts the centre southeast of the 6AM advisory position, and not too far from the Haiti coast. Given proximity to the rugged terrain, and the less than ideal upper level conditions, Hanna will struggle until the long awaited turn to the north or northwest occurs. However, recon have reported a 993mb pressure, and maximum surface winds from SFMR are near 50 mph. If her current motion to the south / southeast con tinues then she may weaken significantly due to the Hispaniola landmass.
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Rich B
SkyWarn UK
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Raymond
Weather Guru
Reged: Wed
Posts: 112
Loc: Germany
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Another fact against (at least short term) restrengthening: Die strong bands to the S/SE are blocked away by the mountains of Hispaniola and blown away to the east by the strong winds. So they can´t wrap around the center!
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shewtinstar
Verified CFHC User
Reged: Mon
Posts: 23
Loc: Jacksonville, Fl
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I would think that with Hanna sitting and churning up the water for all this time that Ike will go into hypothermia shock when he hits it. I am in Jacksonville, Fl and when we are about to get hit with tropical systems my arthritis goes into high gear. I have no body aches or pains at this time. It may not be a science, but the warning systems never let me down before. I have no concerns, at this time, of a hurricane heading this way.
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LoisCane
Veteran Storm Chaser
Reged: Fri
Posts: 1236
Loc: South Florida
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Track is often easier to figure than timing and intensity.
It's not that I don't think Hanna will bounce up again I just think it may take longer than planned as she has gone further south than planned, stayed there longer and has had a lot of interaction with Haiti. Yes, it will pull together but it will take a little bit longer. That throws off the plan if you ask me.
Ike is hauling, steady like so they have to at some time catch up especially as Hanna has to go North a bit.
Ike is far away still... could do the Carib still if it goes WSW under the high but think it's more a lock on Florida or ... eww the Keys... .
Just a note on the WV the dip is pushing to the SE and not abating so I don't see how Hanna gets up and makes a run for anything just yet.
She never made it west enough to bounce up the west side of the diving trough/ULL feature.
http://hadar.cira.colostate.edu/ramsdis/online/trop_ge_wv_ls_0.html
Which I still think is the bigger problem here..and will that be gone FOR SURE by the time Ike gets here. I am beginning to wonder..
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http://hurricaneharbor.blogspot.com/
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doug
Weather Analyst
Reged: Mon
Posts: 1006
Loc: parrish,fl
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The fly in the ointment may be that trough. If my eyes don't deceive me the trough has in fact lifted NE but is leaving a deepening ULL in it wake and that is squarely where Hanna was two days ago. This is uncoupling the LLC from all the convection. Can Hanna survive that? Hanna has had that type of problem all along with an ULL shearing convection last week , then shear from Gustav, and now this. This new feature is more robust than the one she encountered while developing last week and is virtually on top of her. I would not be surprised to see Hanna continue to fade.
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doug
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scottsvb
Weather Master
Reged: Mon
Posts: 1184
Loc: fl
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Yep, I mentioned this in the Hanna lounge from my forecast. Hanna is reforming to her north under the convection flare up. She should be a hurricane again tonight. Watches should be posted by 5pm for the carolinas.
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