ATL : TROPICAL DEPRESSION ERIKA (06L)

[caribsue]

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.

Well said, from a human in one of those islands..... these systems can tear villages apart, cause flooding and landslides. I have heard people say its not a depression or a storm .... then bish bash bosh devastation.

[tolakram]

Refresher.

192500 1807N 05612W 9646 00406 0108 +211 +168 103049 052 042 000 03
192530 1806N 05614W 9641 00410 0107 +210 +169 103049 051 044 000 03
192600 1805N 05616W 9647 00402 0105 +210 +170 101046 046 042 000 00
192630 1804N 05618W 9645 00404 0103 +212 +170 103050 052 043 000 03

or am I looking at the wrong flag?

[carolina_73]

Looking at those models above seems to be hinting towards a possible SC/ NC landfall. (If 94L does not recurve) If it is weak and goes into the Carolinas that would be great news for some folks. Alot of areas are starting to get back into drought mode being down 5+ inches.

[RL3AO]

URNT15 KNHC 011938
AF305 01BBA INVEST HDOB 21 20090901
192700 1804N 05620W 9651 00397 0102 +213 +172 099044 047 041 002 03
192730 1802N 05622W 9641 00407 0101 +214 +173 101048 050 041 000 03
192800 1801N 05623W 9645 00400 0099 +212 +175 101046 047 041 000 03
192830 1800N 05624W 9650 00396 0098 +213 +176 098044 046 039 000 03
192900 1758N 05626W 9646 00398 0097 +215 +177 100047 048 039 000 03
192930 1757N 05627W 9639 00403 0096 +215 +179 100045 046 038 000 00
193000 1755N 05629W 9644 00397 0095 +215 +180 096044 045 039 000 03
193030 1754N 05630W 9647 00394 0093 +215 +181 095043 045 038 002 00
193100 1753N 05632W 9648 00393 0092 +217 +182 097042 043 038 000 03
193130 1751N 05633W 9645 00394 0090 +220 +183 095040 042 037 000 03
193200 1750N 05634W 9643 00395 0090 +220 +184 095039 039 037 000 03
193230 1749N 05636W 9648 00389 0089 +220 +185 093036 037 037 000 03
193300 1747N 05637W 9647 00391 0088 +221 +187 096035 035 036 000 00
193330 1746N 05639W 9639 00396 0087 +225 +188 095033 034 036 000 03
193400 1745N 05640W 9642 00395 0086 +225 +190 092031 032 031 000 00
193430 1743N 05642W 9647 00390 0085 +230 +191 093030 031 031 000 03
193500 1742N 05643W 9646 00389 0084 +233 +192 092030 030 030 000 00
193530 1741N 05644W 9641 00393 0084 +231 +194 092030 030 030 000 03
193600 1739N 05646W 9645 00391 0083 +230 +196 089028 029 031 000 03
193630 1738N 05647W 9642 00391 0083 +227 +198 084028 029 031 000 03
$$
;

[Wthrman13]

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.

Well said, from a human in one of those islands..... these systems can tear villages apart, cause flooding and landslides. I have heard people say its not a depression or a storm .... then bish bash bosh devastation.

The problem is that the LLC is defined in a surface-relative sense, and not in a storm-relative sense. This means that a fast moving but relatively poorly-defined circulation may have strong winds of even TS strength, but no closed circulation relative to the surface. However, in these sorts of cases, in a moving reference frame following the storm motion, the circulation would likely be closed and better defined. In my opinion, this should be how they determine whether the system has "closed off" a circulation enough to be considered a tropical cyclone. This would make those borderline cases of tropical disturbances with TS winds on the north side of the circulation which are screaming westward at 20+ kts into true tropical storms, and help alleviate the problem of perception you mention. Obviously there are some ambiguities involved in how one defines the storm motion vector to begin with, but, as in many other cases in meteorology and science in general, definitions and classifications will always have some level of arbitrariness attached to them.

EDIT: I should point out that I still think that the storm's intensity should be classified with respect to the ground-relative wind speed (since that is what we humans who live on the ground and aren't usually moving very fast relative to it care about ), and not the storm relative. I just think that the *presence or absence* of a circulation center should be considered relative to the storm motion.

[RL3AO]

Refresher.

192500 1807N 05612W 9646 00406 0108 +211 +168 103049 052 042 000 03
192530 1806N 05614W 9641 00410 0107 +210 +169 103049 051 044 000 03
192600 1805N 05616W 9647 00402 0105 +210 +170 101046 046 042 000 00
192630 1804N 05618W 9645 00404 0103 +212 +170 103050 052 043 000 03

or am I looking at the wrong flag?

Thats the flag. 03 means the SFMR data is questionable, not the FL wind data which a few people seem to think. 02 means FL wind data is questionable.

[Chris_in_Tampa]

Need to go, someone else can take over images.

[Stormcenter]

I believe that's a pretty safe bet right now.

12Z ECMWF recurves it east of CONUS. That track looks just about what I would forecast for this thing.

[Bocadude85]

I believe that's a pretty safe bet right now.

12Z ECMWF recurves it east of CONUS. That track looks just about what I would forecast for this thing.

Yes but this run is farther south and west before the recurve.

[wxman57]

EDIT: I should point out that I still think that the storm's intensity should be classified with respect to the ground-relative wind speed (since that is what we humans who live on the ground and aren't usually moving very fast relative to it care about ), and not the storm relative. I just think that the *presence or absence* of a circulation center should be considered relative to the storm motion.

Perhaps I'm not understanding you correctly, but that's how intensity is classified - ground relative. The storm's forward speed isn't a consideration. The plane measure surface wind speeds and that's the intensity. Now it just so happens that if a storm is moving rapidly westward that the winds to the north of the track (measured at the surface) will be considerably higher than the winds south of the track. But all reported wind speeds around a storm are, indeed ground-relative.

[RL3AO]

URNT15 KNHC 011946
AF305 01BBA INVEST HDOB 22 20090901
193700 1737N 05649W 9645 00388 0082 +230 +198 083027 028 031 000 03
193730 1735N 05650W 9647 00386 0081 +230 +199 088028 028 032 000 03
193800 1734N 05651W 9639 00392 0081 +226 +199 083027 028 999 999 03
193830 1732N 05653W 9647 00385 0080 +230 +200 079023 024 030 000 03
193900 1731N 05654W 9646 00385 0080 +229 +200 081020 021 030 000 03
193930 1730N 05656W 9642 00388 0079 +226 +201 080019 019 028 000 03
194000 1728N 05657W 9643 00387 0078 +231 +201 074016 017 999 999 03
194030 1727N 05658W 9644 00385 0077 +229 +202 072016 016 999 999 03
194100 1726N 05700W 9647 00382 0076 +235 +202 061017 018 999 999 03
194130 1725N 05701W 9642 00386 0077 +235 +203 063017 018 999 999 03
194200 1723N 05703W 9643 00386 0077 +230 +204 063017 018 999 999 03
194230 1722N 05704W 9647 00383 0077 +230 +204 065013 014 027 000 03
194300 1721N 05705W 9644 00385 0076 +233 +204 068013 015 999 999 03
194330 1719N 05707W 9647 00382 0076 +234 +204 072011 011 024 000 03
194400 1718N 05708W 9645 00383 0076 +235 +205 076010 011 025 000 03
194430 1717N 05709W 9640 00388 0076 +232 +206 057011 011 022 000 03
194500 1715N 05710W 9650 00379 0075 +237 +206 051009 009 020 000 03
194530 1713N 05711W 9638 00390 0074 +240 +207 043006 006 018 000 03
194600 1712N 05711W 9646 00382 0075 +239 +208 041006 006 017 000 00
194630 1710N 05711W 9645 00384 0075 +238 +209 036004 005 018 000 00
$$
;

[Air Force Met]

again 52kt is flagged

Again...No its not...the SFMR is flagged...not the flight level winds (see my other post on the 94L thread). Also...there is a 43kt SFMR that's NOT flagged. The FL winds are not flagged either...none of them.

[JTD]

I believe that's a pretty safe bet right now.

12Z ECMWF recurves it east of CONUS. That track looks just about what I would forecast for this thing.

Stormcenter, what is your basis for this belief? What models have you looked at? When you look at the upper level air flow charts, model data, projected track so far, and the synoptics, please do elucidate me as to why it is a safe bet that this recurves. Also, it appears to me that you take the most conservative approach imaginable to any system that forms at any time regardless of the circumstances.

A look at Hebert's box will show that storms that cross 20 N at 60 W almost invariably strike the U.S. somewhere. That is a key benchmark. Indeed, I believe a storm crossing at 20 N and 60 W or below has never not hit the US. It's the Hebert theory.

Some models do indicate a recurve at this point but some do not. I am just wondering what your objective evidence is to state that this is a clear recurve?

[artist]

EDIT: I should point out that I still think that the storm's intensity should be classified with respect to the ground-relative wind speed (since that is what we humans who live on the ground and aren't usually moving very fast relative to it care about ), and not the storm relative. I just think that the *presence or absence* of a circulation center should be considered relative to the storm motion.

Perhaps I'm not understanding you correctly, but that's how intensity is classified - ground relative. The storm's forward speed isn't a consideration. The plane measure surface wind speeds and that's the intensity.

What about vorticity being a factor in classification? If you have no vorticity and you have straight line winds coming at you that are as great in strength as a TS or Hurricane,
they would be just as damaging, yet are not given warnings such as a TS,etc.,
I don't know if this is what he is thinking of or not, but my own question.

[JonathanBelles]

The info from this recon flight will go into the 00Z runs tonight, correct?

[RL3AO]

URNT15 KNHC 011957
AF305 01BBA INVEST HDOB 23 20090901
194700 1708N 05711W 9644 00384 0075 +240 +210 014004 004 018 000 03
194730 1706N 05711W 9643 00384 0075 +237 +210 336004 005 019 000 03
194800 1704N 05712W 9645 00384 0075 +235 +211 334004 004 019 000 03
194830 1703N 05712W 9645 00383 0076 +234 +211 305005 005 018 000 03
194900 1701N 05712W 9645 00384 0076 +235 +211 287005 006 018 000 00
194930 1659N 05712W 9652 00377 0076 +232 +211 299005 006 014 001 03
195000 1658N 05713W 9642 00386 0077 +229 +210 283005 006 016 001 00
195030 1657N 05714W 9645 00385 0077 +235 +207 281006 007 020 000 03
195100 1655N 05716W 9645 00385 0077 +235 +206 279007 007 018 000 00
195130 1654N 05717W 9645 00384 0077 +235 +206 282006 007 017 000 03
195200 1653N 05718W 9644 00386 0077 +235 +207 288006 007 999 999 03
195230 1652N 05719W 9645 00385 0077 +235 +207 279008 009 999 999 03
195300 1651N 05721W 9644 00387 0078 +235 +208 278009 009 999 999 03
195330 1649N 05722W 9645 00385 0077 +235 +208 276010 010 999 999 03
195400 1648N 05723W 9644 00387 0078 +235 +209 280011 011 999 999 03
195430 1647N 05724W 9645 00387 0079 +235 +209 284011 011 999 999 03
195500 1646N 05726W 9644 00388 0080 +235 +209 287011 011 999 999 03
195530 1644N 05727W 9646 00387 0080 +235 +209 289010 011 999 999 03
195600 1643N 05728W 9644 00388 0080 +237 +210 297011 011 999 999 03
195630 1642N 05729W 9645 00389 0081 +234 +210 299010 010 999 999 03
$$
;

[Derek Ortt]

no, only G-IV data is used to initialize models

[tolakram]

A look at Hebert's box will show that storms that cross 20 N at 60 W almost invariably strike the U.S. somewhere.

I think you have it backwards. Storms that have hit always go through the box. Big difference.

http://www.hurricanecity.com/hebertbox.htm

The HebertBox was "discovered" in the late 1970s by Paul Hebert (pictured at left). This former nws & nhc forecaster found many major Hurricanes that hit South Florida had to first pass through these boxes.

Wikipedia

http://en.wikipedia.org/wiki/Hebert_box

[ncweatherwizard]

Haven't been really following this thread today since I've been busy, so I may be repeating someone.

UL anticyclone over the center of the disturbance extends to the mid-levels but is tilted. Mid-level portion of the anticyclone is to the south of the disturbance, and mid-level shear is beating the %@#$ out of 94L today. Of course, someone at NHC is weary of naming the storm with convection removed from the center, and this would may would have already be named had Danny not happened so recently.

Given all that, the disturbance is so close to land that I wouldn't want to wait much longer to name it and issue warnings if I could help it. Fortunately though, the worst of the weather is behind the center, and this gives a little more time to take action.

[Wthrman13]

EDIT: I should point out that I still think that the storm's intensity should be classified with respect to the ground-relative wind speed (since that is what we humans who live on the ground and aren't usually moving very fast relative to it care about ), and not the storm relative. I just think that the *presence or absence* of a circulation center should be considered relative to the storm motion.

Perhaps I'm not understanding you correctly, but that's how intensity is classified - ground relative. The storm's forward speed isn't a consideration. The plane measure surface wind speeds and that's the intensity.

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?