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Quiet Atlantic; more on Supertyphoon Saomai

By: Dr. Jeff Masters, 2:11 PM GMT on August 11, 2006

High wind shear continues to dominate the tropical Atlantic, and there's little to be concerned with today. The remains of the tropical wave that the Hurricane Hunters investigated earlier this week as it moved through the Lesser Antilles Islands are just south of Haiti. A hint of a circulation at mid levels of the atmosphere developed this afternoon, but the associated heavy thunderstorm activity is limited. The wave is under about 10-20 knots of wind shear, and any development of this system will be slow.

Supertyphoon Saomai:
In China, the death toll has risen to over 100 in the wake of Supertyphoon Saomai, which slammed into the coast south of Shanghai Thursday as a Category 4 storm with 135 mph winds. The death toll will no doubt rise higher today as the remains of Saomai spread heavy rains through the same region of China hit by Tropical Storm Bilis, which killed more than 600 people last month.


Figure 1. Supertyphoon Saomai as it passed north of Taiwan, August 10, 2006 at 1:22 GMT. At maximum strength, Saomai was a Category 5 storm with 160 mph winds. The image was taken by the Department of Defense F-15 satellite. Image credit: NOAA Environmental Visualization Project.

The media is calling Saomai the worst typhoon to hit China in 50 years, but there is some dispute about just how strong the storm was at landfall. Here is comparison of intensities from three different agencies at Saomai's landfall at 12 GMT August 10:

U.S. Joint Typhoon Warning Center: 1-min sustained winds of 135 mph, Cat 4.
Japan Meteorological Agency: 1-min sustained winds of 100 mph, Cat 2.
Hong Kong Observatory: 1-min sustained winds of 115 mph, Cat 3.

So, these three agencies all using the same satellite data couldn't agree on the strength of this typhoon within two Saffir-Simpson categories! This underscores the difficulty of trying to determine if global warming is causing an increase in Category 4 and 5 hurricanes--even today with much better tools and training, experts still can't agree on storm intensities with the accuracy needed for such a study.

This was discussed in more detail in a paper published this year by Kamahori, Yamazaki, Mannoji, and Takahashi of the the Japan Meteorological Agency (JMA) in the on-line journal Scientific Online Letters on the Atmosphere - a new journal produced by the Meteorological Society of Japan. The study compares typhoon intensities in the Northwest Pacific since 1977 as compiled by the Joint Typhoon Warning Center (JTWC) and the JMA. The JTWC data was used in the famous Webster et. al study from 2005 that found a worldwide 80% increase in Category 4 and 5 tropical cyclones since 1970. A key element of their conclusions was the data from the Northwest Pacific, which make up about 50% of global Category 4 and 5 storms. The JMA group found that using JTWC's dataset, the number of days when a Category 4 or 5 typhoon was present increased from about 10 per year in 1977-90, to 17 per year during 1991-2004--a 70% increase. However, the JMA data for the same time period showed a 40% decrease in Category 4 and 5 typhoon days. The authors concluded, "We do not have sufficient evidence to judge which dataset is reasonable." I would have to agree--until we get a coordinated major re-analysis effort of all the tropical cyclone data for the globe, it is dangerous to make conclusions about whether global warming is causing an increase in tropical cyclone intensities. I think it is likely there has been some increase, but it is nowhere nearly as large as the 80% increase reported by Webster et. al.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

..sweet pic..F-16 ..T-Birds...F-16 old workhorse...
This happened in 1988 and the first hurricane did not form until September 1st:



Also, 1988's Chris struggled for a week before becoming a tropical storm on August 28.
Gotta 9 G pin to go with it.
early sept like pattern setting up point of interest is a possible shift of waves coming off africa over last couple of hrs looks as main wave production taking a turn towards west to nw direction were as since early aug late july there has been a more w sw movement detected in wave flow if this shift occurs some pretty good convection firing up currently over africa may get caught up in this flow and a storm may soon follow
..Nasa doing a field research on the Afican wave production on the continent..believe you can link to it on NASA weblinks....
I heard somebody say the other day (actually I read what somebody wrote) that the African waves roll in off of the Indian Ocean, cross Africa then into the Atlantic. What kind of lows are they...cold core/warm core????
..nothing like kicking the tires & lighting the fires..Yanking & Banking.....9gs ...thatll make ya grunt..
They had me breathe like I was giving birth.
509. edith
hello
Welcome Edith

Things are fairly quite in the tropics so it is a little quite in here.
evening all... nice pic there stormjunkie and micheal nice pic of gilbert
Evening Gulf :)

Those are some cold clouds of the Carolina coast, Gulf.
Night All:
SSTs




cold cloud tops indeed..... this could be the real thing! :)
hey gulfscott
Here is surface observation map of all bouys and ships in the Caribbean Sea.

yea thel and see that lil spot of hot water just off the coast in the SST image?
Evening thel...sure wish we had a visable on t hat and wish the 41002 buoy barometer was up and running...I see they have pushed the repair back from August to Septemeber.

Did you see the picture of Frack, or was it Frick....Finally put them up in the blog with some others.
thats a nice pic of gibert classic pin hole eye
ever see a storm with 3.5" hail!!!

41036 is up SJ Link
Some waves coming off Africa (9:30pmEDT)

SJ..... saw those..... would be nice to have a visible......

very astute point there will about that hotspot and blob in that location......interestig indeed!!!

as for the bouy.... FIX THE DAMN THING!!! PLEASE!!! LOL
3.5"....Now that will put a hurtin on you.

yea will, but I think 41002 is closer to the blob off the Carolina coast.
I was in Cancun just 4 days before it hit. We were out snorkeling when this squall line came through. The rain felt like needles. Anyway, we flew home, and within 2 days the whole area was flattened. Many Americans were still down there and were unable to fly out. We were very lucky.
yes SJ but it got pretty nice gusts to be that far north of it
Bouy, station and ships observation map of the SE USA:

Interesting wind directions off Carolina
Shell, Exxon seek to tame high waves in search for costly oil (highlights)

Wellington: Energy prices have risen so high that New Zealand is inviting Royal Dutch Shell Plc, ExxonMobil Corp and other natural gas producers to send rigs to one of the most inhospitable seas on Earth.

"The easy oil and gas has been found, said Tony Regan, lead consultant with Singapore-based Tri-Zen International Pte, which has advised clients including Shell and BP Plc. "All the oil companies are well aware that theyve got to look further afield, at deeper water, tougher areas.

"Thats where some of the consistently highest waves in the world come from, said Richard Gorman, a scientist at the National Institute of Water and Atmospheric Research in Hamilton, New Zealand.

Shell, Europes No 2 oil company, is exploring in harsher climates as prices above $70 a barrel attract companies to fields for the first time since the oil shocks of the 1970s. The Hague-based producer is leading a $20bn project to get oil from Russias ice-bound Sakhalin island. Bloomberg
water tempt 84.0 F
What's the point on the oil company blog?
theres a NexSat view of the area Link
Did everyone leave?
and they didnt even say bye bye
Oh Well, Everyone have a good night!
Bye Bye...Night Night. One last image for the road...

water off the east cost is hot, heard of several pockets of 90+ degree water off hatteras.
I love that immage of the lightning on the first page.
Quote: "GO SKINS!!!!!!!!!!!!!!!!!!!!!!!!!"

Go shirts!!!!!!!!!
I'm more inclined to believe that 91L will make a comeback than I am to believe anything will come of that area off NC. There's just too much shear!
There is a chance that atleast on TD will develop next week, some where in the Atlantic:

Off the Carolinas
Former 91L
or from the tropical wave train in the atlantic and the ones coming off.

Wind Shear Map:
1
stormwatcher~ I guess you didn't read it. It had some neat descripitions of the unique weater in the region.

Oil companies are being offered the chance to explore 140,000sq miles (362,000sq km) of ocean off New Zealands South Island, in the so-called "Furious 50s and "Screaming 60s. Those latitudes are renowned among sailors for the prevailing westerly winds that circle the globe.

In dead times such as these like through the winter we've commented on the winds in these areas. Cool pic in there too. There's nothing new on Saomai, that's what i had gone looking for.

A partal pass of 91L remenents on QuikSCAT. Unimpressed, one 25kt vector.
ELAliveforthetropic, hello
554. AndyN
Could this be the one:
TROPICAL WAVES...

A TROPICAL WAVE IS ALONG THE W COAST OF AFRICA ALONG 15W S OF
21N MOVING W NEAR 10 KT. THIS WAVE HAS A FAIR AMOUNT OF
SIGNATURE EVIDENT ON SATELLITE IMAGERY AND IS GENERATING SMALL
CLUSTERS OF MODERATE CONVECTION FROM 12N-17N BETWEEN 13W-19W.
EVEN THOUGH THIS WAVE HAS NOT YET PULLED OFF THE CONTINENT THERE
IS GOOD CONFIDENCE IN THIS ANALYZED POSITION BASED UPON THE
AVAILABLE SFC DATA AND SATELLITE IMAGERY WHICH SHOWS A CLASSIC
WAVE STRUCTURE. IN ADDITION...GLOBAL MODELS HAVE THIS WAVE
INITIALIZED WELL AND TRACK IT OFFSHORE TONIGHT EVENTUALLY
PICKING UP FORWARD SPEED AS IT MOVES UNDER A LOW-MID LEVEL RIDGE.
anything interesting happening out there
I guess everyone went out tonight?

There's not as much activity when nobody's yelling at each other or arguing over whether or not some invest is going to survive.
559. AndyN
jphurricane2006: I will say that is the most, how shall I say, confidence displayed in a wave by NHC this year. Already talking about it before it even comes off the coast.
Also a user at FLhurricane indicate there could be something to track next week if this waves holds together.

Conditions most likely will permit for the wave to hold together. (most noticable is the above 80degrees water just off Africa)......
hello..kind of quiet tonight
Hey Y'all! Just got back from an Astros game. Astros win 4-2, and Pitcher Andy Pettite hit his first career home run.

how is this weather related? Well...a southerly wind blew the smoke from the fireworks to the North.
: )
566. AndyN
Any thought from anyone why all the ULL's so far this year? Also, I know if anything gets in the Gulf, lookout...It is very warm....260 NM S of Panama City the Gulf was around 87 degrees...Thanks to the loop current.
JP..shame on her..i guess that you will have to settle for spending time with us. lol

by the way, do I hear rumblings that 91L is trying to rise up from the dead?
How's the tropics going?
91L? That thing is still around?
AndyN glad to see that you survived the storms last night..looked pretty bad.

isn't this the perseid (sp?) meteor showers? when the moon is at a min. there is nothing better than to lay on the beach and watch. the show goes on until sunrise..
ahhh
575. AndyN
Allybama: They petered out before they got here...Although I had to go to Alabama EMA HQ today and hit a big one in Clanton, AL....Flooding rain and a few cloud to ground strikes rather close to my vehicle...
There are only two upper Level Lows in the Atlantic Basin tonight, one in the Gulf of Mexico(Last time I checked) and the other North East of Puerto Rico.

Both are producing shear, but has gradually weakened throughout the week.

Night All......
W. Pac. is dominated by an ULL, which is probably hindering development there.

Link
Hey guys good evening last time i was on jeff master's had just given an update on the possible comeback of 91L but from what i see that comeback was stopped dead on its tracks.Anything new?
does anyone look at the model maps (gfs)
JP,
You been watching the local stations on why little no tropical activity, Tony Manolfi on Wesh said it was because of a strong high and dust pushing storms south of FL, while Glen Richards on Fox said it was because of fronts and troughs? Or is it a mixture of both?? I thought a strong high would keep storms west hitting land opposed to recurving?
I normally check on a regular basis, but I haven't checked recently. Mayby I should

GFS
Both JP
here they are normally most active say midnight until 4 am. do you have an observatory or learning center there? if so, call them tomorrow and they can give you details. you need to be away from the city lights as much as possible.
ITCZ in E. Pac. looks unimpressive

Link
I find it amazing we have this drought in FL, Glenn Richards has repeatingly said it would take a TD or TS to break it? My question then is lets say FL gets zero Tropical activity no waves etc, won't we be in extreme drought by Nov then going back into the dry season?
Atlantic has no major players either.

Link
yes the comeback isn't looking real likely now.

Dry air, dust & shear, mostly from ULLs seems to have kept the season in check. I guess troughs were coming down earlier & disrupted 2 gulf disturbances, but it has been a while.
JP,
Has FL had seasons like this before with so little storms and Tropical activity, I don't remember ever in 5 years being here this extreme drought, t-storms in August are normally a given.
how bad is the drought in FL..we are +20 inches under norm so far..
Thanks JP, we do need some rain though, hopefully no lightning though we are getting brush fiires again! I hope Dr.M addresses this in one of his blogs "dry weather in FL and the tropics and if there is any connection?" I emailed him that earlier this season and he did not really have an answer on that then...Glenn Richards did say above average temps and above average rain, seen the temps not the rain in his outlook...he says the rain will come from the gulf on a SW flow.
JP, I concur with the p/u in trop activity and think that when it does start it will be pretty active. Was it 1996 or 1997 that there were 4 storms in the ATL at one time?
the good news during a drought is the mosquito population is down..even though someone here in Mobile did come down with West Nile last week..
sporteguy03 only 5 years? Jp has a point the state about burnt down in '98. Remember the complete evacuation of Volusia County? The summer we told the tourists don't come here, we're on fire.
This year has been pretty good for cruisin' the tropics! I would give anything to be in St. Thomas right now!!!
I agree allybama iam expecting a quick ramp up in activity in the next 2-3 weeks as we push closer and closer to the heart of the season.
Reminds me of my house after hurricane andrew...all that was left standing was my bathroom.
OK, ya'll are probably going to think that I am crazy but here goes..
I would love to see a storm roll off Africa and reach Cat 5 with winds in excess of 200 mph. I want to see how big one could get - it would just have to die off somewhere in the NATL. I love the hurricane pics on here and find beauty in their symmetry. I told you that..I was crazy..
well night i cant wait to see what this blog will be like when we get are 1st hurricane of the year or 1st cat 4 of the year night
CatChaser..where did the UFO's come from? Oh yea - from all of that swamp gas!! lol
ah some one say cat 5 storm lol


you no all when a cat 5 storm is not overe land hiting any one and only in open water a way from land they can be fun to watch you no why i like to play the game call how low will the mb go its fun game as well
JP - not being nosy (or as stated by Randrewl that I ask too many questions - lol) exactly what is it that you do on the ship? By the way, I love cruises. My husband is taking his sister in Dec when Princess sails from N.O. because I can't get off of work and her hubby can't go either! :(
AllyBama check out my hurricane wilma and katrina photo albums.

Click here to see my Katrina Album

Click here to see my hurricane wilma album
Taz, bring on the games!
Hurricane23 - thanks for posting the pics for me. They are fascinating and beautiful!
No problem
organized - me?!? pleezz..91L was more organized than I am..I don't know how I have made it as long as I have..lol
JP - do you work under contract to be onboard for "X" number of months like the back of the house employees? Just curious. I had thought of working on a cruise ship at one time and understood and it would be a week on/week off, etc.
Good night guys...Have a wonderful night.
632. AndyN
Click on my name. I just uploaded some of the images I ttok on Grand Isle Louisiana while conducting Law Enforcement Ops in support of Hurricane Katrina Response Efforts.
JP - you got mail.

Hey on the long hours, I worked at a casino for several years. Sometimes you don't go home if your relief doesn't show up. I have had to work over 24 hours straight when one of my employees stole money!!
Working in the Casino Cage was not easy..
AndyN - saw your pics. how long you were you in Grand Isle?
JP - you just got a letter..

I guess that we are the only ones left so I will go..leave the porch light on.
639. AndyN
Allybama: Eight days, but went to new orleans a couple of times to escort medical supplies into Jefferson Parish downtown New Orleans....
with 639 comments - this blog is dead!!

R.I.P. 0107 CDT
641. AndyN
TEST
blob popin up just se of windward is. near 12.9 w
also stream to sw another in ne there may be further dev on this any insight on this
643. AndyN
Here is two:
TROPICAL WAVES...
TROPICAL WAVE IS JUST INLAND ALONG THE W COAST OF AFRICA ALONG
16W/17W S OF 21N MOVING W 10-15 KT. WAVE HAS A WELL DEFINED MID
LEVEL ROTATION NEAR 16N ALTHOUGH CONVECTION HAS DIMINISHED OVER
THE PAST FEW HOURS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE
INLAND AND WITHIN 120 NM ALONG THE COAST OF AFRICA FROM 12N-17N.

TROPICAL WAVE IS ALONG 49W/50W S OF 20N MOVING W 15 KT. WAVE
CONTINUES TO HAVE A WELL DEFINED LOW LEVEL INVERTED V-SHAPE
CURVATURE HOWEVER LACKS DEEP CONVECTION DUE A VERY DRY
ENVIRONMENT. ISOLATED THUNDERSTORMS ARE FROM 14N-18N BETWEEN
47W-51W.
very slow start to the year. Can't wait to see whats in store . West central Florida has been lucky in my 30+ years.
I'm out.
646. KRL
So far so good. :)
JMA uses 10-min MSW, not 1-min. In the early years, both JMA and CWB(Taiwan) uses
1-min MSW estimation. Therefore, the intensity of storms seems decreasing in recent
years. But it is not the fact. Moreover, Saomai broke some records on China mainland.
920hPa was measured at Saomai's landing position. The gust measured was 75.8m/s.
(The lowest pressure measured in Taiwan was 912hPa and in Japan was 908hPa)
A quiet tropics and a quiet blog.....
Morning everyone.

TROPICAL STORM FORMATION IS NOT EXPECTED THROUGH SUNDAY.

It's always nice to read that!
Howdy StormW....Quiet isn't it?
I always get the jitters this time of year when it gets like this StormW.
Talking to some old friends yesterday and we all agreed that this lull is only a lull. It's usually like this at this part of August anyway. Isn't it like August 12 or 13 that the graphs show activity picking up? I can't remember where that graph is.
Blobs look diff when you live on a rock in the sea. When you are smashed, there is no Denny's Grand Slam a "few miles up the road" to give you a break. So, guys, please use your energy to keep the blobs way East of 64. Thx.:)
caribqn...I hear that. We may have those conveniences on the mainland but when we get slammed they aren't operating anyway so it really is no benefit. My local pizza guy has a huge generator and opens as soon as the wind dies a little!
Well tropics are quiet again, only 2 areas worth mentioning in the newly updated

Tropical Weather Roundup

Another good and quiet day!
turtlehurricane ...it appears that old 91 was pulled into the upper low. That true?
I dont think upper lows can "pull in" surface features, it may have sheared it towards the center of the upper low giving it the appearence it was pulling in 91L.
StormW...Great. Thanks.
Morning ya'll:)

Anyone check the 06zGFS yet? Still wants to form a system on the tail end of the E coast trough. Now it is hinting at a possible move back towards the N Fla to Obx coast.
good morning boys and girls.....rand..saw tyou say pizza...food of the gods....have yet to dind the "best" place yet...you're any good?
StormJunkie...Morning. I saw the GFS a bit earlier. That scenario has been changing at almost every run. If two runs would say the same thing I would think something is up. Or did I miss one? Anyway local NWS in FL aren't even mentioning it today or yesterday.
ok...turned the light on...much easier to see the keyboard...rand...what i was trying to say was...your pizza joint any good?
ricderr...Pizza....I don't honestly know of a great pizza joint! He's the only place open after a storm so it is very good then!
669. IKE
91L....GONE!!!!!!!!!!!

Tropics are quiet.

Day 73....110 to go and it's over.

May the shear stay with us...maybe we can go all year without a hurricane in the Atlantic.
very true.....remember after jean heading south to find a place to eat
morning all
IKE that would be a nice thought. i live in FL and the insurance companys would still find away to raise rates. IMHO
Well Rand, with an unformed system I doubt they willever say the same thing, but what I find interesting is that several runs have formed something on the tail of this front, as well as the Nogaps at times. And now the fact that the GFS hinted a possible push back to the W in earlier runs, but that is much more evident in the latest run. Just thought it was interesting. Not worth too much yet, execept as an area to keep an eye on.

673. IKE
Posted By: salter at 7:34 AM CDT on August 12, 2006.
morning all
IKE that would be a nice thought. i live in FL and the insurance companys would still find away to raise rates. IMHO


Tell me about it....I'm in the panhandle...my rates are awful.
675. IKE
SJ...the NAM has 2 lows east of Florida in 84 hours..one east of Miami and another..stronger one...1008 mb..east of about JAX...looks like it has it heading toward the Carolinas.
SJ.

EXTENDED PERIOD...MON THROUGH FRI...MODELS HINT THAT TROUGH SLIDES
INTO S FLA MON AND STALLS OVER AREA THROUGH WED...BEFORE ATLC HIGH
PRES REBUILDS W MOVING STALLED BOUNDARY NORTHWARD AND DRIER AIR
MOVES OVER THE AREA. . SINCE THIS IS FIRST RUN SEEN WITH TROUGH MOVING INTO
AREA. WILL NOT GO WHOLE HOG AS GFS GUIDANCE SUGGESTS UNTIL A LITTLE
MORE CONTINUITY ESTABLISHED.

Miami discussion.
SJ.....Jacksonville.

SUN NIGHT AND MON...STEERING FLOW BECOMES ONSHORE AS THE RIDGE TO
OUR NORTH STRENGTHENS OVER GA/N FL...WHILE AN AREA OF LOW PRESSURE
IS FORECAST TO DEVELOP ALONG THE FRONTAL BOUNDARY WELL OFFSHORE OF
THE US COAST.
678. IKE
Per Tampa's morning discussion......On Wednesday the model solutions are becoming more divergent in the
latest runs. Both GFS and dgex keep the remnant moisture from the
dissipated front over the southern half of Florida through Thursday
while also depicting a second frontal boundary forming over the
central states. This new front begins dropping southward by
Wednesday evening. GFS solution is more conservative and brings this
second boundary into northern Florida by Friday early in the
morning. Dgex moves the front faster and brings it over northern and
central Florida by Thursday morning thus combining with the
lingering low level moisture and suggesting good chances of rain
everywhere. Also...the front looks more vigorous on dgex while GFS
depicts a more weaker system barely reaching the northern half of
the County Warning Area. Also...a low level cyclone is shown on both models forming
just east of Florida with dgex again spinning it faster and stronger
than GFS. At this point the forecast will continue to follow the GFS
solution and keeping basically climatology probability of precipitation through Friday and wait
for later model runs to see if GFS begins trending towards the more
aggressive solution shown by dgex.

Well, That covers Florida. Anyone from the Carolinas? That's out of my area.
Can't help myself.

Wilmington:

SURFACE LOW DEVELOPING EAST OF THE GA/SC LINE MOVES AWAY FROM THE
COAST SUNDAY.
GRADIENT RELAXES AS SURFACE HIGH PRESSURE SETTLES OVER
THE WATERS. WINDS WILL DECREASE TO AROUND 10 KT LATE SUNDAY.
Doesn't appear to be anything or anyone agreeing on any of this right now.
IKE
what is the ( dgex )i've never heard of that.
So what is the dgex? That is a new one to me
685. IKE
Posted By: GulfScotsman at 7:54 AM CDT on August 12, 2006.
Posted By: IKE at 12:32 PM GMT on August 12, 2006.
91L....GONE!!!!!!!!!!!

The ghostly well defined mid-low VORTEX remains in tact and very symetrical.

you cannot see it.... but it is there!


OMG!!!!!!!!!

Keep an eye on it.

Darn thing just vanished!
lol Rand, that is why I think it is an area that bears watching a little closer then the normal blob.
687. IKE
Not sure what the dgex is...maybe turtlehurricane knows....

689. IKE
On WV I see a spin SSE of Jamaica. I also see that pesky ULL east of the southern Bahamas.

What I don't understand is why the clouds associated with the former 91L..just vanished? I'm glad, but I don't get it.
690. IKE
GS said>>>But those hot spicey Carribean girls usually do not put on a lot of weight.... no fat ladies singing yet!....that's funny!

They sure do here! Must not be many fast-food joints down there..........
691. IKE
I saw Dr. M's update on here yesterday afternoon at 3:10 CDST.
694. IKE
Dry air w/dew points in the 70's. The dry air must be in the mid/upper levels?
Downscaled GFS with Eta Extension (DGEX)

This is all I know.
So the NAM and the Eta are the same?
StormJunkie...I'm not sure man. Sounds like a good question for the NWS? We should send them this question. Unless anyone on here can answer that. I sure would like to know.
SJ...go here
I am sure that the NAM and ETA are the same thing, this says that they are the same (also notice that the GFS is also called AVN).
Stormjunkie.....
Basically, it's a full 12 km/60 level ETA run imposed on the boundary conditions of the previous GFS run for hours 78-192.

It means that the the GFS is being forced to run on a higher resolution and with better dynamics/physics (ETA-X) from hours 78-192. They use the previous run of the GFS's boundary conditions as it would take too long to wait for the current run.

They're basically combining a wave model (better boundary conditions) with a grid model (better resolution)...and trying to realize the best of both worlds.
I did not write that....lifted from the net for explanational and educational purposes only, no copywrite infringments intended!
What I unedrstand and am trying feebly to remember is the DGEX was an experimental model introduced in 2004. Looks like the NWS is still using it in between GFS runs.
707. IKE
Dr. M has a new blog.