New Terminology for 2010 - "Post-Tropical Cyclones"

[wxman57]

See the link below. I'm not sure how they'll be using the terminology as far as in public advisories, but I'll see Bill Read in 5 weeks at the NHC and can ask then.

http://www.nws.noaa.gov/om/notification ... _terms.txt

Here's a bit of the text:

ON MAY 15 2010...THE NWS WILL BEGIN USING THE TERM /POST-
TROPICAL/ TO DESCRIBE WEATHER SYSTEMS THAT ARE NO LONGER
TROPICAL CYCLONES. THIS CHANGE WILL MAKE NWS TERMINOLOGY
CONSISTENT WITH THE TERMINOLOGY USED BY OTHER WORLD
METEOROLOGICAL ORGANIZATION MEMBER STATES. IT WILL ALSO ALLOW
THE NWS TO MORE ACCURATELY DESCRIBE THE METEOROLOGICAL STRUCTURE
OF FORMER TROPICAL CYCLONES.

THE FOLLOWING DEFINITION FOR POST-TROPICAL CYCLONE WILL BE
INCLUDED IN THIS SEASON/S UPDATE OF NWS INSTRUCTION
10-604: TROPICAL CYCLONE DEFINITIONS.

POST-TROPICAL CYCLONE...A FORMER TROPICAL CYCLONE. THIS GENERIC
TERM DESCRIBES A CYCLONE THAT NO LONGER POSSESSES SUFFICIENT
TROPICAL CHARACTERISTICS TO BE CONSIDERED A TROPICAL CYCLONE.
POST-TROPICAL CYCLONES CAN CONTINUE CARRYING HEAVY RAINS AND
HIGH WINDS. FORMER TROPICAL CYCLONES THAT HAVE BECOME FULLY
EXTRATROPICAL...AS WELL AS REMNANT LOWS...ARE TWO SPECIFIC
CLASSES OF POST-TROPICAL CYCLONES.

AS SUGGESTED BY THE ABOVE DEFINITION...THE NWS WILL CONTINUE TO
USE THE MORE SPECIFIC TERMS OF /REMNANT LOW/ AND /EXTRATROPICAL/
... WHEN APPLICABLE... TO PROVIDE ADDITIONAL INFORMATION ON THE
TYPE OF SYSTEM THE TROPICAL CYCLONE HAS OR IS EXPECTED TO
BECOME. UPDATED DEFINITIONS OF REMNANT LOW AND EXTRATROPICAL
CYCLONE FOLLOW.

REMNANT LOW...A POST-TROPICAL CYCLONE THAT NO LONGER POSSESSES
THE CONVECTIVE ORGANIZATION REQUIRED OF A TROPICAL CYCLONE...AND
HAS MAXIMUM SUSTAINED WINDS OF LESS THAN 34 KNOTS. THE TERM IS
MOST COMMONLY APPLIED TO THE NEARLY DEEP-CONVECTION-FREE SWIRLS
OF STRATOCUMULUS IN THE EASTERN NORTH PACIFIC.

EXTRATROPICAL CYCLONE...A CYCLONE OF ANY INTENSITY FOR WHICH THE
PRIMARY ENERGY SOURCE IS BAROCLINIC /THAT IS...RESULTS FROM THE
TEMPERATURE CONTRAST BETWEEN WARM AND COLD AIR MASSES/.

THE FOLLOWING EXAMPLE SHOWS HOW THE NEW TERMINOLOGY WOULD BE
USED IN THE TABLE SECTION OF A TROPICAL CYCLONE DISCUSSION
PRODUCT FOR THE LAST ADVISORY ON A DECAYING TROPICAL STORM.

IN THIS EXAMPLE...THE SYSTEM HAS LOST THE DEEP CONVECTION
REQUIRED OF A TROPICAL CYCLONE BUT IT DOES NOT YET HAVE ANY
FRONTAL CHARACTERISTICS. IN ADDITION THE SYSTEM CANNOT BE
DESIGNATED A REMNANT LOW BECAUSE ITS MAXIMUM WINDS EXCEED
34 KNOTS. THEREFORE THE SYSTEM IS MERELY DESCRIBED AS
POST-TROPICAL AT THE INITIAL TIME. IN 24 HOURS...HOWEVER...THE
SYSTEM IS FORECAST TO CHANGE STRUCTURE AND BECOME A FRONTAL LOW.
THE /EXTRATROPICAL/ DESIGNATION IS THEREFORE APPENDED IN THE
TABLE TO INDICATE THIS FORECAST CHANGE IN STRUCTURE.

FORECAST POSITIONS AND MAX WINDS

INITIAL 01/1500Z 46.5N 46.5W 40 KT...POST-TROPICAL
12HR VT 02/0000Z 48.9N 45.6W 40 KT...POST-TROPICAL
24HR VT 02/1200Z 52.2N 43.5W 40 KT...POST-TROP/EXTRATROP
36HR VT 03/0000Z 55.0N 39.8W 40 KT...POST-TROP/EXTRATROP
48HR VT 03/1200Z 56.0N 33.0W 40 KT...POST-TROP/EXTRATROP
72HR VT 04/1200Z 56.5N 20.0W 40 KT...POST-TROP/EXTRATROP
96HR VT 05/1200Z...ABSORBED

[HURAKAN]

I like better "former" than "post," but that's just me. I also don't see a problem with just using the word "ex." Ex-Tropical Cyclone. Shorter and even in Spanish ex has the same meaning and sound as in English.

[Hurricanehink]

I like how they just copied the positions and whatnot from the last advisory of Tropical Storm Laura in 2008. As they used that terminology for the first time in Oct. 2008, I am surprised they did not bring it up and introduce it for last season. Also, I wonder if they will retroactively apply that label for any older storms (i.e. put in the best track somehow).

Perhaps Erin 07 would be a good example for post-tropical, for when it was over Oklahoma, since the notice says that remnant lows have winds less than TS force. I just wonder how often the term will be used, since the vast majority of storms in the Atlantic either lose their circulation, lose their winds, or become extratropical. Maybe a storm like Barry 07, which after peaking, lost much of its convection, yet was not extratropical, and it still had TS winds before it made landfall.

[CrazyC83]

Stealing a page from Environment Canada there it looks like. The term is best used for systems difficult to classify (unclear if an extratropical cyclone, a tropical low, etc.) that are not tropical cyclones.

Could a term "pre-tropical" be introduced for storms before developing into a tropical cyclone? Although usually such does not appear on the BT.

[CrazyC83]

Another important change: the SSHS officially (not just experimentally) drops storm surge and flooding from the considerations, becoming strictly winds in official documents as well.

http://www.noaanews.noaa.gov/stories201 ... icane.html

I'd introduce new warnings for storm surges that are completely independent of wind speeds as well (criteria and issuances by the WFOs):

* Storm Surge Advisory - a storm surge is expected to impact the area, but not cause any real flooding problems. It would be issued with 12 to 24 hour lead time.

* Storm Surge Warning - a storm surge that is likely to cause flooding problems is expected within 24 hours (from onset of storm surge warning criteria being reached, not landfall or peak).

* Storm Surge Watch - a storm surge that is likely to cause flooding problems is possible within 36 hours (from onset of storm surge warning criteria being reached, not landfall or peak). Could also be issued for areas adjacent to warnings if the potential exists but is not guaranteed.

* Storm Surge EMERGENCY - a catastrophic storm surge expected to cause enormous damage and potential for large loss of life is expected within 24 hours (from peak).

[wxman57]

Glad that SSHS "experiment" was successful last year. What would have happened if the experiment of removing the misleading surge heights in the SSHS had failed? Put them back in?

I created more realistic surge ranges for each SS category as part of a preparedness presentation. For example, depending upon how large a Cat 2 hurricane is and where a Cat 2 hurricane hits (and angle of the strike & forward speed), the surge could be anywhere from 2-3 feet to 30 feet. So it makes sense to remove surge from the SSHS.