ATL : TROPICAL DEPRESSION ERIKA (06L)

[HURAKAN]

2nd storm we've had go from being an invest directly to a TS this season.

Back to back. Edouard (2002) [also formed on Sep. 1 ] would be very proud of its sister!



Because both looked alike!

[tolakram]

It's one of those issues where someone made up (not to say it isn't accurate) a reasoning for what defines a tropical cyclone, and then used it to determine when certain watches and warnings will be issued.

To me the real question is how well a storm is bringing winds to the surface and what is fueling the storm. If it's an ill defined LLC of a tropical nature that is bringing 50kts winds to the surface then naming it or not naming it is a moot point. Damage is real, lost lives are real.

If nothing else perhaps the best answer might be to expand the warning system to include tropical disturbance warnings.

You want to get peoples attention.

Going back on topic, sorry for the interruption.

[Wthrman13]

Sorry, I wasn't clear. Of course I realize that the winds are reported as ground-relative. My point was that I think that whether or not the system has a closed circulation should be considered in a storm-relative framework, but that the intensity should still be considered (as it is currently) in a ground-relative framework. Does that make sense?

Problem is...there are many times that a system has a storm-relative closed circulation...but yet you won't find any west winds whatsoever. That's not a true cyclone. Waves that are moving west across the Atlantic at 20 kts or more will often have a storm-relative circulation...but they will only have an area of light and variable winds in the CUSP. I wouldn't call that a tropical cyclone because it isn't a closed low...and many times those features will fall apart. There are other types of warnings...other than TS warnings...that a local NWS office could issue that would cover stormy weather associated with the passage of a strong tropical wave.

AFM, but that is exactly my point. Whether or not you define a cyclone based on ground-relative or storm-relative winds is essentially an arbitrary choice. I know that the standard definition is based on the ground-relative wind field. However, consider that a tropical disturbance moving west at 20 kts such that you have weak and ill-defined winds near the cusp, may not be all that different, dynamically speaking, from a similar disturbance that is nearly stationary and would have a much better defined circulation relative to the ground (ignoring the larger scale flow in each case). In the former case, if you subtract out the storm's forward motion, it would look much like the latter's.

What I was getting at in my original statement was that there are many cases of strong tropical waves with TS force winds over a large area that for all intents and purposes are tropical cyclones that happen to be moving too fast (because they are embedded in large-scale fast flow) to have a closed circulation relative to the ground. I have no real problem with defining cyclones based on ground-relative closed circulations, but if it is true that people pay more attention if the system is considered a TC vs. whether it is not, perhaps it would make more sense to take into account the larger scale flow and define the system as a cyclone relative to that.

Not trying to put too fine a point on it; this is essentially an issue of semantics and classification schemes.

EDIT: Ok, after thinking about it a bit more, there is a difference in how the disturbance extracts energy from the underlying ocean between the two cases I mentioned. In the former case more energy is being extracted on the north side, because of the stronger winds there, and in the latter, it's symmetric, so the two are not equivalent, but again this is about how you define a cyclone, and not necessarily the processes that lead to the cyclone's development in the first place.

[deltadog03]

the deep convection to east of the llc is pushing quickly towards it.

[JTD]

784
WTNT31 KNHC 012047
TCPAT1
BULLETIN
TROPICAL STORM ERIKA ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062009
500 PM EDT TUE SEP 01 2009

...ERIKA FORMS EAST OF THE NORTHERN LEEWARD ISLANDS...TROPICAL
STORM WATCHES ISSUED...

AT 5 PM...2100 UTC...THE GOVERNMENT OF THE NETHERLANDS ANTILLES HAS
ISSUED A TROPICAL STORM WATCH FOR THE ISLAND OF ST. MAARTEN.

AT 5 PM...THE GOVERNMENT OF ANTIGUA AND BARBUDA HAS ISSUED A
TROPICAL STORM WATCH FOR THE ISLANDS OF ANTIGUA...BARBUDA...ST.
KITTS...NEVIS...AND ANGUILLA.

AT 5 PM...THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WATCH
FOR THE ISLANDS OF ST. MARTIN AND ST. BARTHELEMY.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 36 HOURS.

INTERESTS ELSEWHERE IN THE NORTHERN LEEWARD ISLANDS...U.S. AND
BRITISH VIRGIN ISLANDS...AND PUERTO RICO SHOULD MONITOR THE
PROGRESS OF ERIKA.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA
OUTSIDE OF THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED
BY YOUR NATIONAL METEOROLOGICAL SERVICE.

AT 500 PM EDT...2100 UTC...THE CENTER OF TROPICAL STORM ERIKA WAS
LOCATED NEAR LATITUDE 17.2 NORTH...LONGITUDE 57.3 WEST OR ABOUT 390
MILES...625 KM...EAST OF THE NORTHERN LEEWARD ISLANDS.

ERIKA IS MOVING TOWARD THE WEST-NORTHWEST NEAR 9 MPH...15 KM/HR...
AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT COUPLE
OF DAYS. ON THIS TRACK THE CENTER OF ERIKA IS EXPECTED TO REMAIN
TO THE NORTHEAST OF THE LEEWARD ISLANDS.

MAXIMUM SUSTAINED WINDS ARE NEAR 50 MPH...85 KM/HR...WITH HIGHER
GUSTS. SOME SLOW STRENGTHENING IS FORECAST DURING THE NEXT COUPLE
OF DAYS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 105 MILES...165 KM
FROM THE CENTER.

THE LATEST MINIMUM CENTRAL PRESSURE REPORTED BY AN AIR FORCE RESERVE
RECONNAISSANCE AIRCRAFT IS 1007 MB...29.74 INCHES.

...SUMMARY OF 500 PM EDT INFORMATION...
LOCATION...17.2N 57.3W
MAXIMUM SUSTAINED WINDS...50 MPH
PRESENT MOVEMENT...WEST-NORTHWEST OR 300 DEGREES AT 9 MPH
MINIMUM CENTRAL PRESSURE...1007 MB

AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE
CENTER AT 800 PM EDT FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 1100
PM EDT.

$$
FORECASTER BLAKE/FRANKLIN

[RL3AO]

URNT15 KNHC 012026
AF305 01BBA INVEST HDOB 26 20090901
201700 1550N 05820W 9642 00402 0093 +236 +219 269014 015 999 999 03
201730 1549N 05819W 9645 00398 0093 +236 +219 263015 016 999 999 03
201800 1548N 05817W 9635 00411 0095 +234 +219 259016 017 999 999 03
201830 1548N 05815W 9646 00400 0096 +235 +219 259016 017 999 999 03
201900 1548N 05812W 9641 00405 0095 +235 +219 254017 017 999 999 03
201930 1548N 05810W 9645 00402 0095 +235 +219 260017 017 999 999 03
202000 1548N 05808W 9645 00401 0095 +235 +219 259017 018 999 999 03
202030 1548N 05806W 9645 00401 0095 +236 +220 258017 017 999 999 03
202100 1548N 05803W 9645 00400 0094 +237 +220 254018 019 999 999 03
202130 1549N 05801W 9643 00402 0094 +236 +220 255017 018 999 999 03
202200 1549N 05759W 9645 00401 0094 +235 +220 252018 019 999 999 03
202230 1549N 05757W 9646 00398 0094 +232 +221 241018 019 999 999 03
202300 1549N 05754W 9645 00399 0094 +232 +221 240019 021 999 999 03
202330 1549N 05752W 9645 00400 0094 +233 +221 245019 019 999 999 03
202400 1549N 05750W 9645 00399 0094 +235 +220 247018 019 999 999 03
202430 1549N 05748W 9645 00400 0093 +235 +220 248018 018 999 999 03
202500 1549N 05745W 9645 00400 0093 +235 +219 237019 020 999 999 03
202530 1549N 05743W 9643 00401 0093 +235 +219 235020 021 999 999 03
202600 1549N 05741W 9644 00400 0093 +235 +219 240020 021 999 999 03
202630 1549N 05739W 9646 00398 0093 +233 +219 236023 024 999 999 03
$$
;

[Evil Jeremy]

Officially Erica on NRL as well! Its go time!

[artist]

Sorry, I wasn't clear. Of course I realize that the winds are reported as ground-relative. My point was that I think that whether or not the system has a closed circulation should be considered in a storm-relative framework, but that the intensity should still be considered (as it is currently) in a ground-relative framework. Does that make sense?

Problem is...there are many times that a system has a storm-relative closed circulation...but yet you won't find any west winds whatsoever. That's not a true cyclone. Waves that are moving west across the Atlantic at 20 kts or more will often have a storm-relative circulation...but they will only have an area of light and variable winds in the CUSP. I wouldn't call that a tropical cyclone because it isn't a closed low...and many times those features will fall apart. There are other types of warnings...other than TS warnings...that a local NWS office could issue that would cover stormy weather associated with the passage of a strong tropical wave.

AFM, but that is exactly my point. Whether or not you define a cyclone based on ground-relative or storm-relative winds is essentially an arbitrary choice. I know that the standard definition is based on the ground-relative wind field. However, consider that a tropical disturbance moving west at 20 kts such that you have weak and ill-defined winds near the cusp, may not be all that different, dynamically speaking, from a similar disturbance that is nearly stationary and would have a much better defined circulation relative to the ground (ignoring the larger scale flow in each case). In the former case, if you subtract out the storm's forward motion, it would look much like the latter's.

What I was getting at in my original statement was that there are many cases of strong tropical waves with TS force winds over a large area that for all intents and purposes are tropical cyclones that happen to be moving too fast (because they are embedded in large-scale fast flow) to have a closed circulation relative to the ground. I have no real problem with defining cyclones based on ground-relative closed circulations, but if it is true that people pay more attention if the system is considered a TC vs. whether it is not, perhaps it would make more sense to take into account the larger scale flow and define the system as a cyclone relative to that.

Not trying to put too fine a point on it; this is essentially an issue of semantics and classification schemes.

EDIT: Ok, after thinking about it a bit more, there is a difference in how the disturbance extracts energy from the underlying ocean between the two cases I mentioned. In the former case more energy is being extracted on the north side, because of the stronger winds there, and in the latter, it's symmetric, so the two are not equivalent, but again this is about how you define a cyclone, and not necessarily the processes that lead to the cyclone's development in the first place.

[HURAKAN]

[Weatherboy1]

some deep convection starting to fire over what MAY be a new center that relocated to the NE a bit...

[Bunkertor]

Need to go, someone else can take over images.

Awesome. Can you give a link ?

[dolebot_Broward_NW]

Eagerly awaiting an official upgrade so I can alert my peeps here at the office without having to wipe egg off.

[CourierPR]

Sorry about that. Correction noted. That said, a storm crossing at 20 N and 60 W or under certainly does need to be watched and to say that it's a "safe bet" that this storm will recurve is not a responsible statement at this time in my opinion.

Your point is well-taken. For anyone to make such bold, sweeping statements at this point is irresponsible but it seems to be happening on a regular basis now.

[jlauderdal]

It's only a matter of time before a "non tropical" tropical storm does significant enough damage that someone has to go back and review the rules. While I understand the need to be scientifically pure, there are humans involved down there on those Islands, and many won't react until it gets the designation.

This disturbance is tropical in nature, so the point is rather moot. In my opinion.

the residents of the islands will react accordingly regardless of a designation, the residents of the USA well that is a different story

[HURAKAN]

Off topic: Jimena downgraded to category 3, 125 mph winds.

[deltadog03]

Well, someone just lit the match again under what will be erika shortly (assuming)

[Blown Away]

The panic button has just been pressed and the SFL news media will reach Cat 5 levels.

[Gustywind]

[Aric Dunn]

some deep convection starting to fire over what MAY be a new center that relocated to the NE a bit...

not a new center.. it has just been pulled towards the convection

[RL3AO]

URNT15 KNHC 012037
AF305 01BBA INVEST HDOB 27 20090901
202700 1549N 05736W 9641 00401 0093 +230 +219 232023 024 999 999 03
202730 1549N 05734W 9645 00398 0092 +232 +219 233027 030 999 999 03
202800 1549N 05732W 9654 00390 0092 +235 +219 233029 029 999 999 03
202830 1550N 05729W 9643 00401 0093 +233 +219 230026 028 999 999 03
202900 1550N 05727W 9645 00401 0093 +230 +219 230026 029 999 999 03
202930 1550N 05725W 9642 00402 0093 +230 +219 222029 030 999 999 03
203000 1550N 05723W 9646 00397 0094 +221 +219 223033 035 999 999 03
203030 1550N 05720W 9634 00409 0095 +217 +216 227033 033 999 999 03
203100 1550N 05718W 9648 00396 0094 +229 +210 226033 033 999 999 03
203130 1550N 05716W 9644 00400 0095 +230 +207 226033 033 999 999 03
203200 1550N 05713W 9645 00399 0097 +213 +207 229034 035 999 999 03
203230 1550N 05711W 9648 00394 0098 +200 +200 224034 035 999 999 03
203300 1550N 05709W 9643 00401 0095 +227 +197 223034 036 999 999 03
203330 1550N 05706W 9646 00398 0095 +225 +193 224034 035 999 999 03
203400 1550N 05704W 9644 00400 0094 +236 +191 224036 037 999 999 03
203430 1550N 05702W 9643 00401 0093 +236 +193 222037 037 999 999 03
203500 1550N 05659W 9644 00402 0094 +236 +197 220037 038 999 999 03
203530 1550N 05657W 9644 00401 0094 +236 +201 218038 039 999 999 03
203600 1551N 05655W 9643 00401 0094 +237 +205 218039 039 999 999 03
203630 1551N 05653W 9646 00399 0094 +238 +208 216039 041 999 999 03
$$
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