The Steering of Dorian

By: Lee Grenci , 3:54 PM GMT on July 26, 2013

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The 5 A.M. discussion from the National Hurricane Center indicated that Tropical Storm Dorian "lost organization" as it encountered southwesterly wind shear and middle- to upper-tropospheric dry air (one of the traditions I learned from the late John Hope was to never use "he" or "she" to describe a named tropical cyclone). NHC's discussion also focused on low- to middle-tropospheric winds associated with the the Atlantic subtropical high-pressure system (06Z GFS model analysis of 700-mb heights early this morning) as the primary steering currents for Tropical Storm Dorian (see the 06Z GFS model analysis of 700-mb heights and 700-mb streamlines below (larger image). At the time, Dorian was moving to the west-northwest at 17 knots.



The 06Z GFS model analysis of 700-mb heights and 700-mb streamlines on July 26, 2013. 700-mb wind speeds are color-coded in knots. Larger image. Courtesy of Penn State.

When I was a young forecaster (a long, long time ago), I typically looked at mid-tropospheric winds as a proxy for the general movement of tropical cyclones. That's because mid-tropospheric winds serve as a rough approximation for the mean airflow in the troposphere. More specifically, old timers like me looked at the winds between 700 mb and 500 mb at a radius of approximately five to seven degrees latitude from the center of the storm (one degree latitude equals 60 nautical miles). As it turns out, winds in the layer from 700 mb to 500 mb often tend to correlate best with the movement of tropical cyclones (at these radii, environmental winds are essentially unaltered by the circulation associated with the tropical cyclone).

Obviously, my approach as a young forecaster was old school. Nonetheless, my simple method had some merit. Indeed, research has shown that a deep-layer mean flow (between 1000 mb to 100 mb, for example) can be used as a tool to assess steering currents (this technique captures the spirit of my old-school approach).

Subtropical highs are not the only features that steer tropical cyclones. Indeed, mid-latitude systems (500-mb troughs, for example) can also steer tropical cyclones as they move poleward from the Tropics. At times, two tropical cyclones can steer each other, assuming that they're close enough for their circulations to interact (the Fujiwhara effect...a topic for a future blog). Finally, tropical cyclones contribute to their own steering, especially when steering currents are rather weak (the Beta effect, which is fodder for another future blog).


The variation of the steering layers for tropical cyclones with minimum central pressure. Larger image. Courtesy of CIMSS and Dr. Chris Velden.

That's all well and good, Grenci, but why did NHC specifically reference "low- to mid-tropospheric winds in their 5 A.M. discussion today? Experience gained from the careful observations of operational forecasters eventually prompted further research aimed at establishing the connection between the minimum pressure of a tropical cyclone and the corresponding depth of the steering layer. The bar graph above (larger image), which displays the minimum pressure of tropical cyclones versus the depth of their steering layers in the Atlantic basin, supports the notion that the steering layer for a tropical depression is shallower and resides lower in the troposphere. In contrast, the steering layer for strong hurricanes is much deeper. The simple physical connection for you to take away after reading my blog is that a weak tropical cyclone (like Dorian) is usually associated with a shallow vortex. Thus, the mean wind in a correspondingly shallow and low-level layer serves as the steering current. As a general rule, the deeper the vortex, the deeper the layer mean that steers the tropical cyclone.


The 09Z analysis of the streamlines designating the mean wind in the layer from 850 mb to 700 mb on July 26, 2013. Larger image. Courtesy of CIMSS.

To get a better sense for the movement of Dorian, focus your attention on the first layer on the left of the bar graph above (central pressure between 1000 mb and 1010 mb). The steering current for Dorian and other similarly weak tropical storms boils down to the mean wind between 850 mb (roughly 5000 feet) and 700 mb (10000 feet). The 09Z analysis from CIMSS (above; larger image) indicates the streamlines of the mean wind in the layer between 850 mb and 700 mb. Wind speeds are color-coded in knots.

At the other end of the spectrum, note the deep steering layers for strong tropical cyclones whose central pressures are lower than 940 mb or range from 940 mb to 949 mb.

I should point out that these results do not include the impact of the Beta effect on the movement of a tropical cyclone. Moreover, other factors such as season, latitude, easterly versus westerly environmental flow, the rates at which the intensity of tropical cyclones changes with time, etc., probably can skew these results a bit, but, as a general rule, the bar graph above will get you in the ballpark in all the ocean basins.

We've come a long way since I was a young forecaster.

Lee

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1228. Relix
I am calling NEXT for us at PR. Hopefully no good waves until later.
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1227. sar2401
Quoting TideWaterWeather:
Avilla says he lives....As i suspected, Dorian still has a small window to get his MOJO back.


"I WAS TEMPTED TO DECLARE DORIAN A REMNANT LOW IN THIS ADVISORY..."

But only just barely. :-) I think it's pretty clear they believe it can keep itself together until about 11 am and then it will be declared a remnant low. Something amazing and fantastic may occur overnight. It's possible but, like I wrote before, if it does, I'm buying a lottery ticket.
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1226. Grothar
I do not see a due west movement. I have seen a consistently WNW movement from the beginning. Regardless of the strength of the system and moving in tandem with the high, I still feel a slight erosion at the end of the run will keep it on a basically WNW motion. I did post 4 times today to not write this one off.

Look at the convection and retreating dry air and the steering currents.




Disclaimer: Due to the age and deteriorating health of the author of the above opinion, take it with a grain of salt. If you take too much salt you will retain water.



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Quoting 1184. Civicane49:
TROPICAL STORM DORIAN DISCUSSION NUMBER 12
...UNTIL DISSIPATION IN ABOUT 4 DAYS...OR HOPEFULLY SOONER.


Gotta love Avila!
Member Since: July 9, 2006 Posts: 184 Comments: 29594
  • This maybe overdone but is that a tiny bit of convergence as it moves over warm waters. I guess the biggest inhibitor was SST. 



1. Cool water
2. Dry air
3. Small size.
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1223. Patrap
Dorian de-cloaking and opening the flue, slowly, with a lil inflow to start the fire.

Member Since: July 3, 2005 Posts: 420 Comments: 127512
Quoting 1210. Some1Has2BtheRookie:




An annular hurricane with a pinwheel eye.


Whoa, that's an impressive feat. I wonder how it's possible.
Member Since: July 9, 2013 Posts: 0 Comments: 579
can we possibly get a circle on the next wave? I'm bored.
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Worth watching to see what Dorian does in about 3 days as it approaches 70W. Some intensity models show the possibility of re-intensification, and environmental conditions shouldn't be too bad in that region. Whatever energy is left could definitely pose a threat to the Bahamas, Cuba, and Florida, so we'll see.

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Quoting 1211. Tazmanian:




any one want too go for a swim I sure the water there at the nort pole is nic and hot

It'd be nice to see a storm like her in the ocean but instead of hitting NC it recurves
Member Since: February 13, 2012 Posts: 11 Comments: 3627
1218. yqt1001
Well it's obvious the NHC doesn't think that Dorian is quite dead, or else "I WAS TEMPTED TO DECLARE DORIAN A REMNANT LOW IN THIS ADVISORY..." would've been "ASCAT DETERMINED THAT DORIAN NO LONGER HAS A CLOSED CIRCULATION" or something like that. I doubt they will wait much longer than 11am tomorrow, so this will be it's last DMAX to turn things around.
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Quoting 1210. Some1Has2BtheRookie:




An annular hurricane with a pinwheel eye.


Agreed. Isabel is the most charismatic, photogenic hurricane ever.
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1216. Thrawst
Quoting 1157. Grothar:


We already are. It will be firing up very soon.
But it is not the convection to the SW to look for, rather the convection to the NW. BlobCon don't fail me now.




BlobCon can fail?!?! :'(
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and Dorian lives I said this would happen
Member Since: June 13, 2009 Posts: 2 Comments: 10891
Quoting 1205. plywoodstatenative:
To those in here who say that they would love to see a major cane. I will say this: For those of us on here that are survivors of Hurricane Andrew or Katrina, systems like that you DO NOT want to have happen all over. You say you want to see a system like that, but what if it were your friends or relatives that had to ride out that system? What then would you say, would you still desire to see one form? Remember this, do not wish for something that you can not yourself live through.


Or Wilma
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Well I'm just checking in on our "Little Dorian" to see if it was RIP or still on Life Support... :o) And Life Support it is as of right Now....

Mean While back on the Ranch the Long Ranger Cleverly decides as a door that Ton toe shot his knob off....



Taco :o)
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Seems to be having no real issues tonight firing new convection; question remains can Dorian expand this convection to encompass the circulation and will this new convection be maintained tomorrow?
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Quoting 1165. bwi:
I'll be watching (ex?) Dorian for a while longer -- any spinner in that area this time of year merits attention.

But meanwhile, I've been having fun following Arctic weather and webcams. This picture is a few days old, but I like the bird on camera effect.





any one want too go for a swim I sure the water there at the nort pole is nic and hot
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Quoting 1158. TimSoCal:
Lots of folks discussing wanting to see the beauty of a major 'cane, so I have a question.

What to you consider the most beautiful/photogenic hurricane you've ever seen? Visual aids would be appreciated.




An annular hurricane with a pinwheel eye.
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1209. sar2401
Quoting Civicane49:
For my area:

HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE HONOLULU HI
308 PM HST FRI JUL 26 2013


...THE NATIONAL WEATHER SERVICE IN HONOLULU HAS ISSUED A FLOOD
POTENTIAL OUTLOOK FOR THE STATE OF HAWAII...

...HEAVY RAIN AND FLASH FLOODING POSSIBLE MONDAY AND TUESDAY...

THE LATEST FORECAST FOR TROPICAL STORM FLOSSIE TAKES THE SYSTEM
OVER THE ISLAND CHAIN EARLY NEXT WEEK AS A WEAKENING TROPICAL
CYCLONE. WHILE FLOSSIE IS EXPECTED TO REMAIN MOVING STEADILY WEST
AS IT PASSES THROUGH THE ISLAND CHAIN...ABUNDANT TROPICAL MOISTURE
DRAWN INTO THE CIRCULATION WILL BRING THE POTENTIAL FOR VERY HEAVY
RAINFALL AND FLASH FLOODING FOR PARTS OF THE STATE ON MONDAY AND
TUESDAY.

THE DETAILS ON THE TIMING AND LOCATION OF THE HEAVY RAIN REMAIN
UNCERTAIN...AND ARE HIGHLY DEPENDENT ON THE EVENTUAL TRACK OF
FLOSSIE. PLEASE STAY TUNED TO NOAA WEATHER RADIO OR LOCAL MEDIA
FOR FURTHER INFORMATION.

AN UPDATED OUTLOOK WILL BE ISSUED BY 4 AM HST SATURDAY...OR SOONER
IF NECESSARY.

FOLLOW US ON FACEBOOK AND TWITTER AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.HONOLU LU.GOV
WWW.TWITTER.COM/NWSHONOLULU

$$

BIRCHARD

Hopefully it will be a good storm, especially for the Big Island, which I know needs the rain. Any idea which islands are expected to affected most? I know the last time I was on Maui, it seemed to flood from even moderate rainstorms.
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Quoting 1158. TimSoCal:
Lots of folks discussing wanting to see the beauty of a major 'cane, so I have a question.

What to you consider the most beautiful/photogenic hurricane you've ever seen? Visual aids would be appreciated.


Cyclone Monica for me.

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Quoting 1189. pottery:

Yeah, but, Grothars got great gumption, generally galvanising gawking geeks, gazing gleefully at great gimages of globs. Getting grizzly though.....


Awesome alliteration, Pottery! Didn't realize you were such the wordsmith. ;)
Member Since: July 9, 2006 Posts: 184 Comments: 29594
Quoting 1200. Grothar:



I'm thinking, I'm thinking. I have a good one, but not blogable.


You can always post the comment and then appeal the ban later ;)
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To those in here who say that they would love to see a major cane. I will say this: For those of us on here that are survivors of Hurricane Andrew or Katrina, systems like that you DO NOT want to have happen all over. You say you want to see a system like that, but what if it were your friends or relatives that had to ride out that system? What then would you say, would you still desire to see one form? Remember this, do not wish for something that you can not yourself live through.
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I'm surprised and im not surprised. Without convection and ASCAT showing open circulation, I expected remnant low. With a history like Dorian's...I expect then to hang on.
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1203. pottery
Quoting BaltimoreBrian:


Very good Pottery! 10 consecutive words in there! However, our rules clearly state that the sentence can ONLY contain alliterative words. But you get a A- :)


:):))

See you guys tomorrow.
Stay safe all.
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Hope that this wave will bring water for my cistern....


Bedtime, but ... going to check out the moon before sleep...



A full Moon can disturb a good night's sleep, scientists believe.


Researchers found evidence of a "lunar influence" in a study of 33 volunteers sleeping in tightly controlled laboratory conditions.

When the Moon was round, the volunteers took longer to nod off and had poorer quality sleep, despite being shut in a darkened room, Current Biology reports..........

Link
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Quoting 1188. DataNerd:
Well holy s**t Avila of all people kept the system online, and possibly rightfully so.

Perhaps right at the brink Dorian is fighting back and re-establishing a new MLC and baro column.




Its Avila not Stewart. I guess we have to wait while the storm does its thang.
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1200. Grothar
Quoting 1189. pottery:

Yeah, but, Grothars got great gumption, generally galvanising gawking geeks, gazing gleefully at great gimages of globs. Getting grizzly though.....



I'm thinking, I'm thinking. I have a good one, but not blogable.
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THE CENTER OF CIRCULATION APPEARS TO BE MOVING WESTWARD AT 19 KNOTS.
THE SYSTEM IS EMBEDDED WITHIN THE DEEP EASTERLIES...AND AS TROPICAL
CYCLONE...REMNANT LOW OR TROUGH...IT WILL CONTINUE TO MOVE WESTWARD
UNTIL DISSIPATION IN ABOUT 4 DAYS...OR HOPEFULLY SOONER.

DOWNCASTER
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Avilla says he lives....As i suspected, Dorian still has a small window to get his MOJO back.
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Quoting 1189. pottery:

Yeah, but, Grothars got great gumption, generally galvanising gawking geeks, gazing gleefully at great gimages of globs. Getting grizzly though.....


Very good Pottery! 10 consecutive words in there! However, our rules clearly state that the sentence can ONLY contain alliterative words. But you get a A- :)
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1196. ncstorm
In this corner we have ships/LGEM standing at a 145LBs and in this corner we have the Euro/GFS standing at a whooping 250LBS..stay tuned ladies and gentlemen for the fight of the century..

SHIPS AND LGEM RE-INTENSIFY THE
CYCLONE A LITTLE BIT BY THE END OF THE FORECAST PERIOD.
HOWEVER...THE OFFICIAL FORECAST IS BIASED TOWARD THE GFS AND THE
ECMWF GLOBAL MODELS WHICH GRADUALLY WEAKEN DORIAN.
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Quoting 1185. Hurricanes305:
Taking a good look at Dorian on WV, satellite, and rainbow. Its seem that the cloud canopy is larger from the old convection. If the storm wants to survive it would need to fire convection where the dry is hitting it the hardest and work on the convective activity around the center which is a smart way to survive it need to work on its force field to stop the bleeding then work its way back inside. I guess Tropical Cyclones aren't mindless zombies like what some may think :)


He is almost past the worst of the dry air, and shear appears to be dropping off now, he just needs some convection to wrap back up
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Will be interesting to see if the convective refire will be enough for the NHC to continue advisories on Dorian for now.
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1193. Pallis
Quoting 1102. mitthbevnuruodo:


I love to see a major hurricane, for the beauty of nature that one is...with it's well formed eye and perfect banding,it's amazing to view. But want it to be a fish storm...in any basin. I have no desire to see it hit anyone.

I think some DO like to see destruction. Some people are just messed up. But I just like to see the beauty of nature..albeit from afar as possible, and not ruining anyone elses lives either. I'm just interested in weather, mother nature and geological events...and do wish there wasn't a human impact with them. It's just unavoidable sometimes sadly though
Really? You guys are emotionally retarded hypocrites! I want to see a category 10 destroy my entire coast because I hate Yankees,jetskis,speedboats,megayachts,tourist traps, seawalls, and condos! I do not care who I piss off, we were here before this was a state. Go home if you don't like it, and take your illegal aliens with you. I say the storm is going on relative track with the computer models and will flare up tomorrow if it reaches the quite warmer water ahead right ahead of it. Wind shear is the only enemy, and the barely visible (Ull?) below it seems to be in tandem.
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Quoting 1158. TimSoCal:
Lots of folks discussing wanting to see the beauty of a major 'cane, so I have a question.

What to you consider the most beautiful/photogenic hurricane you've ever seen? Visual aids would be appreciated.

Isabel was a nice one to see

Member Since: February 13, 2012 Posts: 11 Comments: 3627
Quoting 1176. bwi:


My uninformed opinion is that the only low-level circulation is the one at 48w. That's the one to watch for regeneration in my opinion.


And the advisory has it at 48.1W, where it will be by 11 p.m. EDT.
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1189. pottery
Quoting BaltimoreBrian:


Now it's Grothar's turn to come up with an all-alliterative sentence that is on topic and makes sense AND is grammatically correct with 10 words ;)

Yeah, but, Grothars got great gumption, generally galvanising gawking geeks, gazing gleefully at great gimages of globs. Getting grizzly though.....
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Well holy s**t Avila of all people kept the system online, and possibly rightfully so.

Perhaps right at the brink Dorian is fighting back and re-establishing a new MLC and baro column.
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TROPICAL STORM FLOSSIE DISCUSSION NUMBER 9
NWS NATIONAL HURRICANE CENTER MIAMI FL EP062013
800 PM PDT FRI JUL 26 2013

THERE HAS BEEN LITTLE CHANGE IN THE STRUCTURE OF FLOSSIE SINCE THE
LAST ADVISORY. THE CONVECTIVE PATTERN STILL CONSISTS OF A CENTRAL
DENSE OVERCAST AND BROKEN CURVED BANDS MAINLY TO THE NORTH AND EAST
OF THE CENTER. AN AVERAGE OF THE LATEST SATELLITE INTENSITY
ESTIMATES SUPPORTS HOLDING THE INITIAL WIND SPEED AT 50 KT. THE
TROPICAL STORM IS OVER 26C WATERS AND IT IS FORECAST TO MOVE OVER
EVEN COOLER WATERS DURING THE NEXT COUPLE OF DAYS. THESE LESS
FAVORABLE OCEANIC CONDITIONS SHOULD CAUSE FLOSSIE TO HOLD STEADY IN
STRENGTH OR WEAKEN. EVEN THOUGH THE WATER TEMPERATURES INCREASE
ALONG THE EXPECTED TRACK OF FLOSSIE LATER IN THE FORECAST...
WESTERLY SHEAR AND DRIER AIR SHOULD RESULT IN ADDITIONAL WEAKENING.
THE NHC INTENSITY FORECAST IS VERY SIMILAR TO THE PREVIOUS ONE AND
IS IN GOOD AGREEMENT WITH THE LATEST GUIDANCE.

FLOSSIE REMAINS ON A STEADY WEST-NORTHWESTWARD COURSE...WITH THE
LATEST INITIAL MOTION ESTIMATE BEING 285/16. THIS GENERAL MOTION IS
EXPECTED TO CONTINUE FOR THE NEXT DAY...FOLLOWED BY A TURN TO THE
WEST WITH SOME DECREASE IN FORWARD SPEED. THE NHC TRACK FORECAST
BRINGS THE WEAKENING STORM NEAR THE HAWAIIAN ISLANDS IN ABOUT 3
DAYS. THE OFFICIAL FORECAST IS AN UPDATE OF THE PREVIOUS ONE AND
VERY CLOSE TO THE MULTI-MODEL CONSENSUS TVCE.

FORECAST POSITIONS AND MAX WINDS

INIT 27/0300Z 17.0N 135.7W 50 KT 60 MPH
12H 27/1200Z 17.6N 138.2W 50 KT 60 MPH
24H 28/0000Z 18.4N 141.4W 50 KT 60 MPH
36H 28/1200Z 19.0N 144.6W 45 KT 50 MPH
48H 29/0000Z 19.5N 147.7W 40 KT 45 MPH
72H 30/0000Z 19.8N 153.9W 35 KT 40 MPH
96H 31/0000Z 20.0N 160.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 01/0000Z...DISSIPATED

$$
FORECASTER CANGIALOSI
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BULLETIN
TROPICAL STORM FLOSSIE ADVISORY NUMBER 9
NWS NATIONAL HURRICANE CENTER MIAMI FL EP062013
800 PM PDT FRI JUL 26 2013

...FLOSSIE MAINTAINING ITS STRENGTH...


SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...17.0N 135.7W
ABOUT 1285 MI...2070 KM E OF HILO HAWAII
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 18 MPH...30 KM/H
MINIMUM CENTRAL PRESSURE...999 MB...29.50 INCHES
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Taking a good look at Dorian on WV, satellite, and rainbow. Its seem that the cloud canopy is larger from the old convection. If the storm wants to survive it would need to fire convection where the dry is hitting it the hardest and work on the convective activity around the center which is a smart way to survive it need to work on its force field to stop the bleeding then work its way back inside. I guess Tropical Cyclones aren't mindless zombies like what some may think :)
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TROPICAL STORM DORIAN DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042013
1100 PM AST FRI JUL 26 2013

DORIAN APPEARS TO STILL HAVE A VIGOROUS LOW- TO MID-LEVEL
CIRCULATION IN CONVENTIONAL SATELLITE IMAGERY WITH 30 TO 35 KNOTS
MEASURED BY A RECENT ASCAT PASS...BUT IT HAS BEEN DEVOID OF DEEP
CONVECTION FOR SEVERAL HOURS. I WAS TEMPTED TO DECLARE DORIAN A
REMNANT LOW IN THIS ADVISORY...BUT GIVEN THE FACT THAT THE
CIRCULATION IS MOVING OVER WARMER WATERS AND SHEAR IS FORECAST TO
LESSEN...NEW CONVECTION COULD REDEVELOP. THE BEST OPTION IS TO KEEP
THE CYCLONE FOR A COUPLE OF MORE ADVISORY CYCLES AND MONITOR THE
EVOLUTION OF THE CONVECTION. SHIPS AND LGEM RE-INTENSIFY THE
CYCLONE A LITTLE BIT BY THE END OF THE FORECAST PERIOD.
HOWEVER...THE OFFICIAL FORECAST IS BIASED TOWARD THE GFS AND THE
ECMWF GLOBAL MODELS WHICH GRADUALLY WEAKEN DORIAN.

THE CENTER OF CIRCULATION APPEARS TO BE MOVING WESTWARD AT 19 KNOTS.
THE SYSTEM IS EMBEDDED WITHIN THE DEEP EASTERLIES...AND AS TROPICAL
CYCLONE...REMNANT LOW OR TROUGH...IT WILL CONTINUE TO MOVE WESTWARD
UNTIL DISSIPATION IN ABOUT 4 DAYS...OR HOPEFULLY SOONER.

FORECAST POSITIONS AND MAX WINDS

INIT 27/0300Z 17.9N 48.1W 35 KT 40 MPH
12H 27/1200Z 18.3N 51.2W 30 KT 35 MPH
24H 28/0000Z 18.8N 55.5W 30 KT 35 MPH
36H 28/1200Z 19.3N 59.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 29/0000Z 20.0N 63.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 30/0000Z 21.0N 70.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 31/0000Z...DISSIPATED

$$
FORECASTER AVILA
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BULLETIN
TROPICAL STORM DORIAN ADVISORY NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042013
1100 PM AST FRI JUL 26 2013

...DORIAN FORECAST TO BECOME A REMNANT LOW IN A DAY OR SO...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...17.9N 48.1W
ABOUT 985 MI...1585 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 22 MPH...35 KM/H
MINIMUM CENTRAL PRESSURE...1010 MB...29.83 INCHES
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11 p.m. advisory already out.
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ROPICAL STORM DORIAN DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042013
1100 PM AST FRI JUL 26 2013

DORIAN APPEARS TO STILL HAVE A VIGOROUS LOW- TO MID-LEVEL
CIRCULATION IN CONVENTIONAL SATELLITE IMAGERY WITH 30 TO 35 KNOTS
MEASURED BY A RECENT ASCAT PASS...BUT IT HAS BEEN DEVOID OF DEEP
CONVECTION FOR SEVERAL HOURS. I WAS TEMPTED TO DECLARE DORIAN A
REMNANT LOW IN THIS ADVISORY...BUT GIVEN THE FACT THAT THE
CIRCULATION IS MOVING OVER WARMER WATERS AND SHEAR IS FORECAST TO
LESSEN...NEW CONVECTION COULD REDEVELOP. THE BEST OPTION IS TO KEEP
THE CYCLONE FOR A COUPLE OF MORE ADVISORY CYCLES AND MONITOR THE
EVOLUTION OF THE CONVECTION. SHIPS AND LGEM RE-INTENSIFY THE
CYCLONE A LITTLE BIT BY THE END OF THE FORECAST PERIOD.
HOWEVER...THE OFFICIAL FORECAST IS BIASED TOWARD THE GFS AND THE
ECMWF GLOBAL MODELS WHICH GRADUALLY WEAKEN DORIAN.

THE CENTER OF CIRCULATION APPEARS TO BE MOVING WESTWARD AT 19 KNOTS.
THE SYSTEM IS EMBEDDED WITHIN THE DEEP EASTERLIES...AND AS TROPICAL
CYCLONE...REMNANT LOW OR TROUGH...IT WILL CONTINUE TO MOVE WESTWARD
UNTIL DISSIPATION IN ABOUT 4 DAYS...OR HOPEFULLY SOONER.

FORECAST POSITIONS AND MAX WINDS

INIT 27/0300Z 17.9N 48.1W 35 KT 40 MPH
12H 27/1200Z 18.3N 51.2W 30 KT 35 MPH
24H 28/0000Z 18.8N 55.5W 30 KT 35 MPH
36H 28/1200Z 19.3N 59.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 29/0000Z 20.0N 63.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 30/0000Z 21.0N 70.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 31/0000Z...DISSIPATED

$$
FORECASTER AVILA
Member Since: September 23, 2005 Posts: 14 Comments: 10870
It still a TS!
Member Since: July 6, 2013 Posts: 0 Comments: 460
1179. ncstorm
ahh..this was posted so much on WU..I still find it hilarious..

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Not much hope here

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.