Hurricane Helene - Cat. 3

[wzrgirl1]

if you look at the archives andrew was never forecasted to curve out to sea.....derek was correct, but at some point about 5 days out, he was expected to turn north

[Canelaw99]

WOW! Strange to read this after all this time knowing what finally happened:

"ZCZC MIAWRKAD4 LOC
TTAA00 KNHC DDHHMM
...FOR INTERGOVERNMENTAL USE ONLY...
TROPICAL STORM ANDREW DISCUSSION NUMBER 12
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT WED AUG 19 1992

POST RECONNAISSANCE SATELLITE PICTURES THIS AFTERNOON HAVE SHOWN ARC
CLOUDS WHICH MAY INDICATE 12 HOURS OR SO OF LITTLE CHANGE IN
STRENGTH. ACTUALLY... THE PULSATING SYSTEM STILL HAS TO GO THROUGH
ONE MORE NIGHT OF SOMEWHAT HOSTILE WINDS ALOFT. IF ANDREW IS NOT
TOO DAMAGED AFTER THAT... THERE IS A POTENTIAL FOR STRENGTHENING FOR
THE REMAINDER OF THE FORECAST PERIOD.

THE INITIAL MOTION IS 295/18 KNOTS. THE OFFICIAL FORECAST IS A
BLEND OF QLM...THE BAM RUNS...AND NHC90. AVN GUIDANCE INDICATES
RIDGING OVER THE EASTERN UNITED STATES AND NORTH OF ANDREW LATE IN
THE PERIOD WITH ANDREW EXPECTED TO BE JUST SOUTH OF THE RIDGE AXIS.
WHILE THIS SCENARIO WOULD TEND TO SUPPORT CONTINUED SLOW WESTWARD
MOTION BEYOND THIS FORECAST...IT IS MUCH TOO EARLY TO SPECULATE
WHETHER ANDREW WILL MAKE LANDFALL...IF AT ALL.

GERRISH"

Guess it proves that NHC is completely human and can only go by what data and knowledge they have, all the while understanding that nature will do whatever it pleases in the end....

Will be interesting to see what Helene has in store over the coming days.

[Damar91]

WOW! Strange to read this after all this time knowing what finally happened:

"ZCZC MIAWRKAD4 LOC
TTAA00 KNHC DDHHMM
...FOR INTERGOVERNMENTAL USE ONLY...
TROPICAL STORM ANDREW DISCUSSION NUMBER 12
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT WED AUG 19 1992

POST RECONNAISSANCE SATELLITE PICTURES THIS AFTERNOON HAVE SHOWN ARC
CLOUDS WHICH MAY INDICATE 12 HOURS OR SO OF LITTLE CHANGE IN
STRENGTH. ACTUALLY... THE PULSATING SYSTEM STILL HAS TO GO THROUGH
ONE MORE NIGHT OF SOMEWHAT HOSTILE WINDS ALOFT. IF ANDREW IS NOT
TOO DAMAGED AFTER THAT... THERE IS A POTENTIAL FOR STRENGTHENING FOR
THE REMAINDER OF THE FORECAST PERIOD.

THE INITIAL MOTION IS 295/18 KNOTS. THE OFFICIAL FORECAST IS A
BLEND OF QLM...THE BAM RUNS...AND NHC90. AVN GUIDANCE INDICATES
RIDGING OVER THE EASTERN UNITED STATES AND NORTH OF ANDREW LATE IN
THE PERIOD WITH ANDREW EXPECTED TO BE JUST SOUTH OF THE RIDGE AXIS.
WHILE THIS SCENARIO WOULD TEND TO SUPPORT CONTINUED SLOW WESTWARD
MOTION BEYOND THIS FORECAST...IT IS MUCH TOO EARLY TO SPECULATE
WHETHER ANDREW WILL MAKE LANDFALL...IF AT ALL.

GERRISH"

Guess it proves that NHC is completely human and can only go by what data and knowledge they have, all the while understanding that nature will do whatever it pleases in the end....

Will be interesting to see what Helene has in store over the coming days.

Smartest post I've seen all day.

[wxman57]

...FOR INTERGOVERNMENTAL USE ONLY...
TROPICAL STORM ANDREW DISCUSSION NUMBER 12
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT WED AUG 19 1992

.....
THE INITIAL MOTION IS 295/18 KNOTS. THE OFFICIAL FORECAST IS A
BLEND OF QLM...THE BAM RUNS...AND NHC90. AVN GUIDANCE INDICATES
RIDGING OVER THE EASTERN UNITED STATES AND NORTH OF ANDREW LATE IN
THE PERIOD WITH ANDREW EXPECTED TO BE JUST SOUTH OF THE RIDGE AXIS.
WHILE THIS SCENARIO WOULD TEND TO SUPPORT CONTINUED SLOW WESTWARD
MOTION BEYOND THIS FORECAST...IT IS MUCH TOO EARLY TO SPECULATE
WHETHER ANDREW WILL MAKE LANDFALL...IF AT ALL.

GERRISH"

Just shows that they had very little model data to look at back then. The BAM models are simple trajectory models that shouldn't be used in the area where Andrew was. The NHC90 model was an old climatology-based model, it only looked at the storm's location and where past storms moved to from that location. The AVN was the only dynamic model they had, and it only went out 48 hours back then, I believe. Looks like the AVN was correct.[/i]

[AJC3]

...FOR INTERGOVERNMENTAL USE ONLY...
TROPICAL STORM ANDREW DISCUSSION NUMBER 12
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT WED AUG 19 1992

.....
THE INITIAL MOTION IS 295/18 KNOTS. THE OFFICIAL FORECAST IS A
BLEND OF QLM...THE BAM RUNS...AND NHC90. AVN GUIDANCE INDICATES
RIDGING OVER THE EASTERN UNITED STATES AND NORTH OF ANDREW LATE IN
THE PERIOD WITH ANDREW EXPECTED TO BE JUST SOUTH OF THE RIDGE AXIS.
WHILE THIS SCENARIO WOULD TEND TO SUPPORT CONTINUED SLOW WESTWARD
MOTION BEYOND THIS FORECAST...IT IS MUCH TOO EARLY TO SPECULATE
WHETHER ANDREW WILL MAKE LANDFALL...IF AT ALL.

GERRISH"

Just shows that they had very little model data to look at back then. The BAM models are simple trajectory models that shouldn't be used in the area where Andrew was. The NHC90 model was an old climatology-based model, it only looked at the storm's location and where past storms moved to from that location. The AVN was the only dynamic model they had, and it only went out 48 hours back then, I believe. Looks like the AVN was correct.[/i]

I am drudging up memories of DIFAX sheets hanging up on the wall. I THINK, and don't quote me on this, the old AVN went out to either 60 or 72 hours.

[Nimbus]

Doesn't seem to be any weakness developing near 50w - 60w just the subtropical ridge wedging itself west. Almost over Puerto Rico now?

http://www.ssd.noaa.gov/goes/east/natl/loop-wv.html

I really hope some of that cool dry air from up around 30N gets down here in Florida later in the week.

[sma10]

if you look at the archives andrew was never forecasted to curve out to sea.....derek was correct, but at some point about 5 days out, he was expected to turn north

And he DID turn north. And then turned west.

[JonathanBelles]

does anyone have a steering currents map?

[wxman57]

I am drudging up memories of DIFAX sheets hanging up on the wall. I THINK, and don't quote me on this, the old AVN went out to either 60 or 72 hours.

I remember that there was only a 500mb chart posted for the 72 and 84-hr periods back then. I think the baroclinic went out to 60 hours, but it wasn't good for tropical.

Yes, I remember the chart walls. Back in the 1980s, we allowed smoking in our office. One of our forecasters set the map wall on fire with a cigarette. Those were the good old days...

[wxman57]

does anyone have a steering currents map?

Here you go, an 18Z GFS projection for early Monday afternoon. Note the deep trof racing into Helene and all the flow away from the east U.S. Coast early next weeek:

http://myweb.cableone.net/nolasue/heleneflow.gif

[Lowpressure]

The 11 p.m. advisory/ discussion is going to open up a pandoras box on this site for all the westward moving questions.

[Bgator]

Given that the
mid-latitude flow across the northern U.S. And the North Atlantic
is forecast by all the models to be fast zonal flow...less
amplification of the trough seems more reasonable...which should
decrease the effect of any northward steering flow on the wast side
of the trough. The result is that the steering flow should weaken
considerably by 96 and 120 hours as mid-level ridging builds slowly
westward to the north of Helene.


THis is from the 11PM discussion, if mid level ridging build over helene, wouldnt it be forced west?

[wxman57]

The 11 p.m. advisory/ discussion is going to open up a pandoras box on this site for all the westward moving questions.

Careful what you read into that NHC talk about westward movement. They're not talking about Helene coming west toward the east U.S. Coast, just stalling for a bit between trofs. They're only addressing the 96-120hr period. That's the FIRST trof they're talking about lifting out early next week. It's the second much stronger trof that moves off the east coast toward the middle of next week that'll turn Helene northward. But that's aroun day 6-7 - beyond the NHC forecast period.

[Brent]

does anyone have a steering currents map?

Here you go, an 18Z GFS projection for early Monday afternoon. Note the deep trof racing into Helene and all the flow away from the east U.S. Coast early next weeek:

http://myweb.cableone.net/nolasue/heleneflow.gif

She's not going into that wall, that's for sure.

[sma10]

Given that the
mid-latitude flow across the northern U.S. And the North Atlantic
is forecast by all the models to be fast zonal flow...less
amplification of the trough seems more reasonable...which should
decrease the effect of any northward steering flow on the wast side
of the trough. The result is that the steering flow should weaken
considerably by 96 and 120 hours as mid-level ridging builds slowly
westward to the north of Helene.


THis is from the 11PM discussion, if mid level ridging build over helene, wouldnt it be forced west?

The answer to your question is right in that paragraph:

"...the steering flow should weaken considerably...."

[HurricaneHunter914]

The track has been shifted southward a bit. Looks like Helene is trying get her shot to be a big hurricane like her Older Brother Gordon.

[Derek Ortt]

they also had the GFDL for Andrew, but I believe it was only run once or twice a day and was experimental then

[CrazyC83]

What I am sensing here:

-Continue westward, missing the Lesser Antilles just to the north

-Trough comes in and steers Helene between Bermuda and the East Coast, missing land

[fci]

Andrew was ALWAYS forecast to turn to the west and intensify. No NHC forecast EVER had it going out to sea

I don't think that was the case with them ALWAYS forecasting the West turn..
They has it going NW and not turning to the west.
Had it all the way up to 28 and 70; not going out to sea but going NW.

Taken from Discussion Archive:
http://www.nhc.noaa.gov/archive/storm_w ... /tropdisc/

Discussion 17 had him all the way up to 28N/70W 72 hours out.
Now; subsequent Discussions started moving the 72 hour out forecast further south and west.

By Discussion 22 they started talking Northern Bahamas and the SE US coast.

[sma10]

I don't think that was the case with them ALWAYS forecasting the West turn..
They has it going NW and not turning to the west.
Had it all the way up to 28 and 70; not going out to sea but going NW.

Taken from Discussion Archive:
http://www.nhc.noaa.gov/archive/storm_w ... /tropdisc/

Discussion 17 had him all the way up to 28N/70W 72 hours out.
Now; subsequent Discussions started moving the 72 hour out forecast further south and west.

By Discussion 22 they started talking Northern Bahamas and the SE US coast.

Absolutely correct, fci.

Simply put, it really was not until Andrew was already under the influence of the high that it was understood how strong the high would be. Admittedly, the track was definitely unusual. Andrew made the turn while at 25.9N and made landfall at 25.4N. It takes quite a ridge to send a hurricane that far west like a bullet while losing a bit of latitude.