Possible subtropical cyclone off South Africa?
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Possible subtropical cyclone off South Africa?
I can't take credit for first noticing this (that should go to Chacor), but there's a really interesting low off South Africa. It looks almost subtropical in nature:
The 18z models also indicate that it has a shallow warm core:
GFS - http://moe.met.fsu.edu/cyclonephase/gfs ... 18/10.html
UKMET - http://moe.met.fsu.edu/cyclonephase/ukm ... 18/24.html
The 12z CMC shows it with a cold core, and the 12z NOGAPS makes it appear to be ex-Indlala (which, when compared to the other tracks, seems kind of odd).
The 18z models also indicate that it has a shallow warm core:
GFS - http://moe.met.fsu.edu/cyclonephase/gfs ... 18/10.html
UKMET - http://moe.met.fsu.edu/cyclonephase/ukm ... 18/24.html
The 12z CMC shows it with a cold core, and the 12z NOGAPS makes it appear to be ex-Indlala (which, when compared to the other tracks, seems kind of odd).
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Philippe Caroff of Met-France has kindly responded (within 4 hours!) to my email regarding this (well, to be more precise, regarding the boundaries of MF's warning area, which I thought was up to 30S, but it's apparently been extended to 40S).
It seems that, according to him, this system had baroclinic origins, but it was in warm waters, therefore convection developed, and he feels that transition to a subtropical cyclone is not impossible, and I quote, "in this case we might decide to warn on it".
It seems that, according to him, this system had baroclinic origins, but it was in warm waters, therefore convection developed, and he feels that transition to a subtropical cyclone is not impossible, and I quote, "in this case we might decide to warn on it".
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- MississippiHurricane
- ChatStaff
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As far as I know, no. From what I can tell, cyclones either dissipate inland over southern Africa or recurve southeastward and out to sea, though there has been at least one that came close:
They wouldn't survive long on the other side due to shear and marginal SSTs, and they wouldn't be able to round the tip due to the subtropical westerlies.
They wouldn't survive long on the other side due to shear and marginal SSTs, and they wouldn't be able to round the tip due to the subtropical westerlies.
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P.K. wrote:When, if ever, did RSMC La Reunion last warn for a subtropical system. I know the operational manual contains the phrase "subtropical disturbance" but that is it and it certainly isn't mentioned on their public page on the types of systems.
I'm not sure, that's why I asked if they would warn on it.
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- Meso
- Category 5
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Hah,this storm created some really big swells off the coast of Durban,doing lots of damage to the beaches and areas there was a spring high tied accompanied with the cut off low it was pretty huge.
What this was,was a cold front supported with sharp trough that developed into a cut-off low which remained stationary for a while.See a few of them every few years.This one deepened a bit more than usual though
Here is a short local press release on it : http://www.weathersa.co.za/Pressroom/20 ... r20KZN.jsp
Article : http://www.news24.com/News24/South_Afri ... 47,00.html
And here is what AJC3 was talking about : http://www.weathersa.co.za/Pressroom/20 ... CEline.jsp
What this was,was a cold front supported with sharp trough that developed into a cut-off low which remained stationary for a while.See a few of them every few years.This one deepened a bit more than usual though
Here is a short local press release on it : http://www.weathersa.co.za/Pressroom/20 ... r20KZN.jsp
Article : http://www.news24.com/News24/South_Afri ... 47,00.html
And here is what AJC3 was talking about : http://www.weathersa.co.za/Pressroom/20 ... CEline.jsp
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Interestingly, SAB issued one Hebert-Poteat classification, at 0900Z today:
20/0900 UTC 34.5S 36.7E ST2.5/2.5 99S -- South Indian Ocean
WWIO21 KNES 200935
SATELLITE WEATHER BULLETIN
SOUTH INDIAN OCEAN MET-7 VIS/IRDAY
.
MARCH 20 2007 0900Z
.
34.6S 36.7E ST2.5 SUBTROPICAL DISTURBANCE
.
PAST POSITIONS....NEWLY DEVELOPED DISTURBANCE
.
REMARKS....FLORIDA STATE UNIVERSITY CYCLONE PHASE DIAGRAMS BASED
ON 00Z MAR 20 RUN OF THE GFS INDICATE THE SYSTEM SOUTH SOUTHWEST
OF MADAGASCAR POSSESSES A NOMINAL SHALLOW WARM CORE STRUCTURE.
CONSISTENT WITH SUBTROPICAL SYSTEMS MOST OF THE CONVECTION IS
LOCATED EAST AND POLEWARD OF THE CENTER...BY 1 TO 1.5 DEGREES
LATITUDE. QUIKSCAT DATA FROM 0336Z SUPPORTS AN INTENSITY OF 35-
40 KNOTS.
.
POSITION ACCURATE WITHIN 40 NMI
.
THE NEXT BULLETIN WILL BE ISSUED BY 20/1600Z.
.
FOR AREAL DISPLAY OF RAINFALL POTENTIAL SEE OUR WEB SITE AT
HTTP://WWW.SSD.NOAA.GOV/PS/TROP/TRAP-IMG.HTML
ALL LOWER CASE LETTERS EXCEPT PS/TROP
.
TURK
.
NNNN
20/0900 UTC 34.5S 36.7E ST2.5/2.5 99S -- South Indian Ocean
WWIO21 KNES 200935
SATELLITE WEATHER BULLETIN
SOUTH INDIAN OCEAN MET-7 VIS/IRDAY
.
MARCH 20 2007 0900Z
.
34.6S 36.7E ST2.5 SUBTROPICAL DISTURBANCE
.
PAST POSITIONS....NEWLY DEVELOPED DISTURBANCE
.
REMARKS....FLORIDA STATE UNIVERSITY CYCLONE PHASE DIAGRAMS BASED
ON 00Z MAR 20 RUN OF THE GFS INDICATE THE SYSTEM SOUTH SOUTHWEST
OF MADAGASCAR POSSESSES A NOMINAL SHALLOW WARM CORE STRUCTURE.
CONSISTENT WITH SUBTROPICAL SYSTEMS MOST OF THE CONVECTION IS
LOCATED EAST AND POLEWARD OF THE CENTER...BY 1 TO 1.5 DEGREES
LATITUDE. QUIKSCAT DATA FROM 0336Z SUPPORTS AN INTENSITY OF 35-
40 KNOTS.
.
POSITION ACCURATE WITHIN 40 NMI
.
THE NEXT BULLETIN WILL BE ISSUED BY 20/1600Z.
.
FOR AREAL DISPLAY OF RAINFALL POTENTIAL SEE OUR WEB SITE AT
HTTP://WWW.SSD.NOAA.GOV/PS/TROP/TRAP-IMG.HTML
ALL LOWER CASE LETTERS EXCEPT PS/TROP
.
TURK
.
NNNN
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20/1430 UTC 35.6S 37.0E ST2.5/2.5 99S -- South Indian Ocean
WWIO21 KNES 201500
SATELLITE WEATHER BULLETIN
SOUTH INDIAN OCEAN MET-7 VIS/IRDAY
.
MARCH 20 2007 1430Z
.
35.6S 37.1E ST2.5 SUBTROPICAL DISTURBANCE
.
PAST POSITIONS....34.6S 36.7E 20/0900Z IRDAY/VIS
.
REMARKS....FLORIDA STATE UNIVERSITY CYCLONE PHASE DIAGRAMS BASED
ON 00Z MARCH 20 RUN OF THE GFS INDICATES THE SYSTEM SOUTH
SOUTHWEST OF MADAGASCAR POSSESSES A NOMINAL SHALLOW WARM CORE
STRUCTURE. CONSISTENT WITH SUBTROPICAL SYSTEMS MOST OF THE
CONVECTION IS LOCATED EAST AND POLEWARD OF THE CENTER...BY 1-1.5
DEGREES LATITUDE.
.
POSITION ACCURATE WITHIN 40 NMI.
.
THE NEXT BULLETIN WILL BE ISSUED BY 20/2200Z
.
FOR AREAL DISPLAY OF RAINFALL POTENTIAL SEE OUR WEB SITE AT
HTTP://WWW.SSD.NOAA.GOV/PS/TROP/TRAP-IMG.HTML
ALL LOWER CASE LETTERS EXCEPT PS/TROP
.
KIBLER
.
NNNN
WWIO21 KNES 201500
SATELLITE WEATHER BULLETIN
SOUTH INDIAN OCEAN MET-7 VIS/IRDAY
.
MARCH 20 2007 1430Z
.
35.6S 37.1E ST2.5 SUBTROPICAL DISTURBANCE
.
PAST POSITIONS....34.6S 36.7E 20/0900Z IRDAY/VIS
.
REMARKS....FLORIDA STATE UNIVERSITY CYCLONE PHASE DIAGRAMS BASED
ON 00Z MARCH 20 RUN OF THE GFS INDICATES THE SYSTEM SOUTH
SOUTHWEST OF MADAGASCAR POSSESSES A NOMINAL SHALLOW WARM CORE
STRUCTURE. CONSISTENT WITH SUBTROPICAL SYSTEMS MOST OF THE
CONVECTION IS LOCATED EAST AND POLEWARD OF THE CENTER...BY 1-1.5
DEGREES LATITUDE.
.
POSITION ACCURATE WITHIN 40 NMI.
.
THE NEXT BULLETIN WILL BE ISSUED BY 20/2200Z
.
FOR AREAL DISPLAY OF RAINFALL POTENTIAL SEE OUR WEB SITE AT
HTTP://WWW.SSD.NOAA.GOV/PS/TROP/TRAP-IMG.HTML
ALL LOWER CASE LETTERS EXCEPT PS/TROP
.
KIBLER
.
NNNN
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- P.K.
- Professional-Met
- Posts: 5149
- Joined: Thu Sep 23, 2004 5:57 pm
- Location: Watford, England
- Contact:
It was given a ST2.5 this afternoon but is down to ST1.5 with this being the last bulletin.
SATELLITE WEATHER BULLETIN
SOUTH INDIAN OCEAN MET-7 IRNIGHT
.
MARCH 21 2007 1900Z
.
36.6S 41.0E ST1.5 SUBTROPICAL DISTURBANCE
.
PAST POSITIONS...36.6S 38.5E 21/0830Z VIS/IRDAY
35.6S 37.1E 20/1430Z IRNIGHT
.
REMARKS...SYSTEM CONTINUES TO WEAKEN. LOCATED LOW LEVEL
CIRCULATION WITH THE AID OF QUIKSCAT WINDS.
.
POSITION ACCURATE WITHIN 60 NMI.
.
THIS IS THE FINAL BULLETIN.
.
FOR AREAL DISPLAY OF RAINFALL POTENTIAL SEE OUR WEB SITE AT
HTTP://WWW.SSD.NOAA.GOV/PS/TROP/TRAP-IMG.HTML
ALL LOWER CASE LETTERS EXCEPT PS/TROP
.
BROWN
SATELLITE WEATHER BULLETIN
SOUTH INDIAN OCEAN MET-7 IRNIGHT
.
MARCH 21 2007 1900Z
.
36.6S 41.0E ST1.5 SUBTROPICAL DISTURBANCE
.
PAST POSITIONS...36.6S 38.5E 21/0830Z VIS/IRDAY
35.6S 37.1E 20/1430Z IRNIGHT
.
REMARKS...SYSTEM CONTINUES TO WEAKEN. LOCATED LOW LEVEL
CIRCULATION WITH THE AID OF QUIKSCAT WINDS.
.
POSITION ACCURATE WITHIN 60 NMI.
.
THIS IS THE FINAL BULLETIN.
.
FOR AREAL DISPLAY OF RAINFALL POTENTIAL SEE OUR WEB SITE AT
HTTP://WWW.SSD.NOAA.GOV/PS/TROP/TRAP-IMG.HTML
ALL LOWER CASE LETTERS EXCEPT PS/TROP
.
BROWN
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