Tropics are (insert trite phrase here). Well, they are active. Summary for 30 August 2018.

It’s the peak of the Northern Hemisphere hurricane/typhoon season.  Here’s the big picture as of noon Eastern US Time (literally – this is a composite of multiple geosynchronous satellites; that’s why there is that black rectangle over the north pole, which isn’t visible from even 22,800 miles high …):

In the Atlantic, “Potential Tropical Cyclone Six,” as NHC is presently calling it, is an organizing tropical wave that has just exited the coast of Africa.  Here is what the GFS model thinks it is going to do, it will probably be called “Florence” by this evening, and is on the fast track to become a hurricane by this weekend.  Carry around a seltzer bottle and squirt the first person who talks about its chances of hitting the US; it’s on the other side of the ocean right now!

In the Pacific, Norman is a mature hurricane making waves off the coast of Mexico, headed west.  Not a threat to anything for at least a week, and probably not then either.

Miriam gave the folks in Hawai’i a bit of a nervous fit, given what just happened with Lane, but it is turning north and likely to die in cold water.

The main threat to land right now is Typhoon Jebi, which is headed towards Japan.  Japan has been hit with multiple very rainy tropical systems this year – last count I saw was over 300 dead from flooding, thousands homeless.  They really don’t need this, hopefully this forecast is off and it will turn offshore.



Lane moving away from Hawaii

Lane has deteriorated to an exposed low level circulation, with all the main convection hundreds of miles to the east – unfortunately, still over the islands of Hawai’i.  Things should hopefully start to clear out later today, although there is a big area of convection still moving over the region.  Rain has been historic in places, and the Big Island hit hard with flooding, but all of the islands have seen a lot of rain, and there is ongoing risk for flooding on the already hard hit (from floods this spring) island of Kaua’i.  Here is an InfraRed satellite view from 7:30am east coast time (1:30am Hawai’i time).    Lane will virtually disappear today, but may come back in a couple of days as an extratropical system of some kind.

Lane falls apart but still dumping rain on Hawaii

Lane is now a tropical storm, and as (nervously!) expected hit a wall of wind shear and what is left of it will begin moving off to the west, away from the Islands today (overnight, Hawai’i time).  If you look at a satellite image like this one from around Midnight Hawai’i time (6am East Coast Time), you might think the storm is directly over the islands …

… but in fact, the center of circulation is well offshore.  Here is the same image, but with the winds from the surface to 5000 feet in yellow, and the winds at about 24,000 feet in blue.

The very strong west to east winds higher up in the atmosphere have pushed all of the stronger thunderstorms and rain away from the center (you will see the phrase “Low Level Circulation Center” or LLCC in the weather service discussions).  Radar is even more dramatic, showing most of the rain still over the Big Island even though the storm is moving away …

Lane should continue to fall apart over the next day or so as it drifts away from the main Islands.  It might become an extratropical storm in a few days.  In any event, rain will continue to fall on the islands of Hawai’i for at least another day, with flooding the continuing danger.

Damage from the storm will likely be mostly from floods, with some scattered impacts from trees down and power outages.  Some of the flooding is already catastrophic, and parts of the Islands (Kaua’i for instance) have been drenched already this year and will likely see further damage.  But if you aren’t in a flooded area this storm probably didn’t seem so bad.  Overall impacts currently estimated in the $100 Million range – but flood impacts are much harder to model than wind, so that’s a pretty iffy number.

CPHC did a good job with this one – difficult scenario, with a strong storm headed towards a heavily populated Island.  Although the metoerology was pretty solid that Lane would not make a direct hit on O’ahu and turn away, still had to be nerve-racking because this is complex stuff with lots of uncertainty.  I didn’t have much of a chance to check any of the media coverage from Hawai’i.  What I did see here on the mainland was mostly of the “their gonna die, lets talk about politics” variety.  Sigh.

Hurricane Lane: waiting game for Hawaii

Here’s a sunrise visual band image of Lane – eye is no longer visible as it continues to weaken, now a Category 2, should continue to fall apart in the shear.

Although there is some risk Lane will hit O’ahu as a Category 1 hurricane tomorrow, it seems much more likely to turn at the last minute, and wind was not really the big risk from this storm, it was/is rain. There is serious flooding on the big island, the question now is how much will fall on the other islands.  Here’s the current (12:30pm ET/6:30am Hawai’i) radar composite.  Not the clear banding you think of from hurricanes, but that’s deceptive.  The storm isn’t moving very fast, so bad conditions should persist through Saturday.  Those cells can dump a huge amount of water as they are forced “upslope” by the terrain, causing massive runoff and flash floods.

Bottom line is that if you are near a stream or river, or a place that floods (or right on the shore), this is a serious, life threatening storm.  Otherwise, it’s probably still much more likely to be a power outage and pick-up-limbs-and-debris after it passes kind of storm.

Hurricane Lane turns north towards main Hawaii islands, expected to turn west away from Oahu

The Central Pacific Hurricane Center is probably a very sweaty smelly place these days 🙂  Hurricane Lane is following the forecast track so far, but it is swinging dangerously close to the Islands.  Here is the latest forecast impact swath based on the 24 August 09z CPHC forecast, which is 11pm the 23rd Hawai’i time and 5am East Coast Time the 24th.  Not much has changed in the last few cycles other than tweaking the intensity and exact track.  CPHC is being a bit conservative (high) with the intensity, but it’s a smart move given how close the storm is passing, how warm the water is, and how organized the storm remains despite a lot of wind shear.  That shear will change direction radically over the next day, forcing a hard left turn as the storm approaches O’ahu.  Scary stuff.

Assuming the storm makes the turn as forecast, in most places impacts will be in the “hazardous to be out in it but not catastrophic” range, except in flood prone areas; see below. The higher winds should stay offshore.  Not to say it won’t get gusty, and higher winds across the higher ridge lines, but wind damage should be limited to limbs and weaker trees down, damage to signage, roofs and awnings, that sort of things.  Could be lots of power outages, but nothing catastrophic unless something breaks that shouldn’t.

The biggest risk from Lane continues to be rain and flash flooding in the mountains and streams/rivers that run off from them.  Some areas have had nearly two feet of rain over the last day – all that water gets channeled through valleys and can cause epic, fast moving floods.  More on that in a separate post.

Small track/intensity shift for Lane, more potential damage for Hawaii

The latest CPHC forecast has Lane staying stronger, and passing a little closer, to the main Hawai’ian Islands.  Moloka’i, Lana’i, and O’ahu are now within the sustained tropical storm force wind swath (40 to 50mph, with wind gusts likely in the 70’s – note that it doesn’t make sense to talk about “hurricane force wind gusts” because the gusts are part of the winds, but that is a rant and battle I think I’ve lost to the media frenzy).  This means there will be more damage and power outages over the islands than estimated based on this morning’s track.  It’s not likely the winds will reach actual hurricane force except on exposed ridgelines and higher elevations, but the danger of that is still present and all preparations should, as CPHC says, “be rushed to completion.”  Lane is still not likely to cause catastrophic damage from wind alone, but in the “hazardous and inconvenient” range in most places. Along the immediate coast there will be storm surge and epic waves.  Inland, however, rain and flash flooding are another matter – this is potentially life threatening.  The slow speed turn and wet character of the storm, combined with enhancement of rain rates from mountainous topography means that is the most dangerous aspect of the storm.  Those in the danger zone (especially valleys and river/stream banks prone to flash floods) need to take this very seriously.  Here’s the latest swath map …

On this track impacts are likely to be in the $100 Million range across the islands.  But as noted, this is a tough storm to get a handle on as small wobbles can either spare the islands – or smash them.

Hurricane Lane Thursday 23 August Impact Forecast for Hawaii

Not too much changed in the outlook overnight.  While Lane remains a Category 4 hurricane (125 kt/145mph winds), it should begin to more rapidly weaken as it passes just south of the Islands.  Here is the predicted wind swath map based on this mornings CPHC forecast:

On this track, aside from higher elevations and ridgelines, sustained winds should stay at or just below tropical storm force.  Lane will take about three days to pass the islands – that’s a long time for it to dump rain, and due to an effect called orographic amplification, there is a big risk of flooding and landslides.  Orographic amplification is caused by  warm moist air being forced upwards by higher terrain (“orography”), causing it to cool and drop out excess moisture.  In the case of tropical systems, it can take an already wet storm and double the rain rates or more on the upwind side (the downwind side is dried out to a corresponding degree).  Here’s a radar composite using the two stations on Hawai’i (at South Point/Naalehu and Upolu Point/North Kohala ) showing the first rain bands passing over the Big Island … due to the mountains, there are “gaps” in the coverage

Damage is *very* dependent on the exact track and rain totals.  Wobbles one way or the other matter a lot in this case, and exact timing of the sharp west turn can cause the damage to change by a factor of ten for only a 20 or 30 mile further north track shift, since it causes impacts on the densely developed south coast of Oahu to come in to play!  If you include economic impacts, the impacts are already in the 10’s of millions of dollars due to preparations, tourism, etc.  The long term impacts (once things settle out, some impacts will be recovered) will likely be in that range, but if the storm shifts even a little further north, or something breaks that shouldn’t, impacts in the 100’s of millions are very possible.

While we’re obsessing over Hawai’i, we shouldn’t forget that Japan – where flooding has killed hundreds this year – is being dumped on by another Typhoon, and and South Korea is being hit today as well.


Hurricane Lane 18Z forecast update for Hawai’i

The latest model runs shifted a bit closer to the Islands, and the turn away from Oahu isn’t forecast to happen as soon.  Here’s the latest forecast impact map …

I don’t envy CPHC on this one.  The models are showing a sharp left turn just before the storm reaches Oahu, and this seems reasonable, but the model guidance is uncertain.  The current best brings the center 30 miles closer to Honolulu than this morning, thus the damage estimate has increased from around the low millions of dollars to between 20 and 50 million.  Still not a huge impact, but a later turn and/or even a little less decay than shown could easily spike that into the hundreds of millions in impacts.  It should be noted that the CPHC forecast holds the intensity above hurricane strength longer than most of the models, but this is a dangerous storm, and a direct hit on the main Islands is not by any means out of the question, so caution is warranted …

Hurricane Lane Wednesday Afternoon ET Update

The sun has risen over Hurricane Lane – it’s a classic hurricane structure …

Not a lot of change in the forecast track or impacts.  The best guess right now is that Lane will pass just south of the Islands, and turn away, weakening rapidly, at the last minute.  But if you live in Hawaii, don’t count on it – plan for a hit just in case …

Hurricane Lane and Hawaii Impact Forecast 22 Aug

Hurricane Lane is a powerful storm located just south of the Big Island of Hawai’i.  Here’s the latest (715am ET, 115am HT) infrared satellite image with radar overlay …

… and here is the latest forecast track from the Central Pacific Hurricane Center (CPHC), with the Haetta/TC impact model forecast (Haetta/TC is a new model I’m working on):

On this track the worst of the impacts should stay well south of the Islands, with impact estimates currently in the low millions of dollars.  However, this track is a reminder of the scary bad Hurricane Iniki from 1992.  Here is the Inki track and impact, with the current forecast for Lane by comparison:

Inki caused about $5 Billion in adjusted damage and devastated the island of Kaua’i.  Lane is forecast to weaken as it turns away (a turn which seems to be starting), but a wobble or drift to the right could cause significant damage to the state.  There are warnings up for the Big Island, where tropical storm force winds are forecast for late today or early tomorrow (Hawai’i time).  A watch is up for the rest of the islands, with the worst conditions expected on Thursday, but everyone should be wrapping up their preparations for a drift in the wrong direction from the forecast track …