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Tropical Depression Don


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Nice overlay... looks like the center is on the NE side of the convective blob.

Best upper level divergence and mid-level vorticity is on the eastern edge of the convective blob, and strongest shear is west of it. So, the further east the llc, the better (for development). That being said, the current presentation is indicative of a bit of easterly shear, which makes sense given the wind analysis.

EDIT: Looks like shear is more northerly than easterly, and the CoC is more on the north end of the convection than the east end. Serves me right for only taking a quick glance at first.

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Ugh, when are SFMR obs not rain-contaminated?

That's the nature of flying into a tropical cyclone. arrowheadsmiley.png

It is pretty easy to tell what is rain contaminated looking at the obs... because the rainfall rate is always associated with each SFMR ob. When the rainfall rate is low (from 0 to around 5mm) it could generally be considered not rain contaminated unless otherwise noted. Anything beyond that value though should be taken with a grain of salt.

Its easy to see how the rain contamination influences the values... below and at 5mm the highest SFMR winds recorded thus far have been around 32 knots... but there are a slew of observations above 35 knots for rainfall rates between 10-15mm.

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One of the odder sets of data I have seen from Recon. Very light winds north of the system (never going above 20kts out of the North East), then a much stronger southern part with 40kt west winds. Rather strange for a system heading westward. Pressure down around 1006mb, though not the center

185800 2211N 08716W 9751 00300 0093 +225 +156 044006 008 011 000 00

185830 2210N 08714W 9753 00298 0092 +229 +154 027006 006 006 000 03

185900 2209N 08713W 9751 00299 0090 +232 +153 348005 006 004 001 00

185930 2208N 08711W 9750 00296 0088 +236 +153 314007 008 006 000 00

190000 2207N 08710W 9755 00292 0087 +227 +154 301011 013 008 001 00

190030 2205N 08708W 9750 00295 0086 +225 +156 299013 014 011 003 00

190100 2204N 08706W 9754 00290 0085 +227 +156 301018 019 013 004 00

190130 2203N 08705W 9753 00288 0081 +228 +157 303020 023 020 004 00

190200 2203N 08705W 9753 00288 0077 +226 +157 297023 023 024 006 00

190230 2201N 08702W 9733 00301 0075 +228 +157 285026 028 025 004 00

190300 2200N 08700W 9737 00295 0071 +238 +156 280029 030 023 003 03

190330 2159N 08659W 9729 00298 0066 +247 +155 271033 034 028 003 00

190400 2158N 08657W 9741 00285 0064 +245 +155 262036 038 030 000 03

190430 2156N 08656W 9732 00296 0066 +241 +157 264039 040 028 001 00

190500 2155N 08655W 9735 00298 0071 +235 +158 267038 039 026 002 00

190530 2153N 08654W 9741 00298 0078 +228 +157 262035 036 021 003 00

190600 2152N 08653W 9740 00301 0082 +221 +156 261033 033 024 005 00

190630 2151N 08652W 9736 00305 0084 +218 +153 259033 033 024 006 00

190700 2149N 08651W 9733 00310 0086 +221 +150 256035 038 025 009 03

190730 2148N 08650W 9743 00300 0091 +202 +147 250038 039 022 017 03

It's because of the light northerly shear over the system resulting in the best convection and associated organization/winds south of the center.

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45kt SE winds at flight level on the NE Quad.

Great example of rain contamination with the SFMR in that last set, where the precip rate was 22 mm/hr, it shot up to 57kts, but otherwise, between 35-40kts

000

URNT15 KNHC 271937

AF300 01DDA INVEST HDOB 17 20110727

192800 2157N 08622W 9760 00298 0102 +204 +137 163038 041 038 014 00

192830 2159N 08622W 9768 00287 0102 +192 +136 156041 045 057 022 03 Significant rain contamination here

192900 2201N 08622W 9753 00299 0101 +190 +136 159039 040 043 017 00

192930 2203N 08622W 9768 00290 0103 +191 +134 154038 040 041 009 00

193000 2205N 08622W 9752 00304 0101 +195 +133 151038 040 037 009 00

193030 2207N 08622W 9762 00292 0099 +208 +132 151039 041 034 009 00

193100 2209N 08622W 9759 00295 0101 +199 +132 148039 040 037 009 03

193130 2210N 08623W 9760 00293 0100 +191 +131 145039 040 038 007 00

193200 2212N 08624W 9758 00296 0100 +189 +131 145040 041 038 007 00

193230 2214N 08625W 9753 00299 0097 +200 +130 150040 041 037 004 00

193300 2215N 08626W 9764 00290 0097 +212 +130 144040 041 035 002 00

193330 2217N 08626W 9764 00290 0096 +217 +130 146041 042 035 002 00

193400 2219N 08627W 9762 00292 0096 +215 +131 145039 039 037 002 00

193430 2221N 08628W 9761 00293 0096 +215 +133 142039 039 038 003 00

193500 2222N 08629W 9762 00294 0098 +219 +136 142036 037 035 004 00

193530 2224N 08629W 9763 00293 0097 +220 +138 140036 036 034 005 00

193600 2226N 08630W 9763 00293 0097 +221 +141 138036 037 032 005 00

193630 2227N 08631W 9761 00295 0098 +223 +143 136034 035 031 004 00

193700 2229N 08632W 9763 00293 0097 +222 +146 133033 033 031 005 00

193730 2231N 08632W 9761 00296 0098 +216 +148 132033 034 031 005 03

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That's the nature of flying into a tropical cyclone. arrowheadsmiley.png

It is pretty easy to tell what is rain contaminated looking at the obs... because the rainfall rate is always associated with each SFMR ob. When the rainfall rate is low (from 0 to around 5mm) it could generally be considered not rain contaminated unless otherwise noted. Anything beyond that value though should be taken with a grain of salt.

Its easy to see how the rain contamination influences the values... below and at 5mm the highest SFMR winds recorded thus far have been around 32 knots... but there are a slew of observations above 35 knots for rainfall rates between 10-15mm.

Are rainfall rates measured in millimeters per hour?

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Based on this and HDOB 17, we'd have a TS.

That's the nature of flying into a tropical cyclone. arrowheadsmiley.png

It is pretty easy to tell what is rain contaminated looking at the obs... because the rainfall rate is always associated with each SFMR ob. When the rainfall rate is low (from 0 to around 5mm) it could generally be considered not rain contaminated unless otherwise noted. Anything beyond that value though should be taken with a grain of salt.

Its easy to see how the rain contamination influences the values... below and at 5mm the highest SFMR winds recorded thus far have been around 32 knots... but there are a slew of observations above 35 knots for rainfall rates between 10-15mm.

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Yep.

latest set of obs shows some 35+ knot SFMR winds with a low rainfall rate... could be enough to upgrade to Don.

Fun! Texas needs the rain. Heck Memphis needs Texas to get the rain, which should finally help the dry heat that has been over the plains this summer, and help with a pattern change away from this ridging in the plains which makes the weather totally boring in Memphis.

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45kt SE winds at flight level on the NE Quad.

Great example of rain contamination with the SFMR in that last set, where the precip rate was 22 mm/hr, it shot up to 57kts, but otherwise, between 35-40kts

000

URNT15 KNHC 271937

AF300 01DDA INVEST HDOB 17 20110727

192800 2157N 08622W 9760 00298 0102 +204 +137 163038 041 038 014 00

192830 2159N 08622W 9768 00287 0102 +192 +136 156041 045 057 022 03

192900 2201N 08622W 9753 00299 0101 +190 +136 159039 040 043 017 00

192930 2203N 08622W 9768 00290 0103 +191 +134 154038 040 041 009 00

193000 2205N 08622W 9752 00304 0101 +195 +133 151038 040 037 009 00

193030 2207N 08622W 9762 00292 0099 +208 +132 151039 041 034 009 00

193100 2209N 08622W 9759 00295 0101 +199 +132 148039 040 037 009 03

193130 2210N 08623W 9760 00293 0100 +191 +131 145039 040 038 007 00

193200 2212N 08624W 9758 00296 0100 +189 +131 145040 041 038 007 00

193230 2214N 08625W 9753 00299 0097 +200 +130 150040 041 037 004 00

193300 2215N 08626W 9764 00290 0097 +212 +130 144040 041 035 002 00

193330 2217N 08626W 9764 00290 0096 +217 +130 146041 042 035 002 00

193400 2219N 08627W 9762 00292 0096 +215 +131 145039 039 037 002 00

193430 2221N 08628W 9761 00293 0096 +215 +133 142039 039 038 003 00

193500 2222N 08629W 9762 00294 0098 +219 +136 142036 037 035 004 00

193530 2224N 08629W 9763 00293 0097 +220 +138 140036 036 034 005 00

193600 2226N 08630W 9763 00293 0097 +221 +141 138036 037 032 005 00

193630 2227N 08631W 9761 00295 0098 +223 +143 136034 035 031 004 00

193700 2229N 08632W 9763 00293 0097 +222 +146 133033 033 031 005 00

193730 2231N 08632W 9761 00296 0098 +216 +148 132033 034 031 005 03

I bolded the SFMR readings that you can consider to not be rain contaminated... plenty of observations are above 35 knots this pass.

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Center found this time, looks to be about 1001mb

195800 2207N 08701W 9746 00276 0058 +231 +165 321013 014 017 003 00

195830 2207N 08659W 9744 00276 0056 +225 +166 332018 021 023 002 00

195900 2207N 08657W 9720 00293 0051 +225 +165 351019 020 022 002 00

195930 2207N 08656W 9728 00278 0041 +242 +163 338023 024 023 000 00

200000 2207N 08654W 9712 00283 0029 +250 +162 334027 029 025 001 00

200030 2207N 08652W 9695 00288 0018 +248 +164 337019 024 021 002 00

200100 2208N 08651W 9742 00245 0015 +250 +168 358008 012 008 002 00

200130 2208N 08649W 9778 00203 0009 +241 +172 084007 009 007 001 03

200200 2208N 08647W 9777 00209 0011 +238 +175 187016 023 005 001 03

200230 2208N 08647W 9777 00209 0017 +236 +177 214026 030 029 002 03

200300 2206N 08649W 9775 00211 0014 +237 +180 229022 025 035 001 00

200330 2206N 08650W 9760 00228 0018 +235 +180 262024 026 040 002 03

200400 2205N 08651W 9765 00228 0026 +241 +180 284032 034 037 002 00

200430 2204N 08653W 9785 00218 0034 +233 +179 283032 032 035 003 03

200500 2204N 08654W 9764 00245 0041 +226 +179 292032 035 034 001 00

200530 2203N 08655W 9766 00245 0046 +229 +177 296029 030 031 002 00

200600 2202N 08657W 9772 00249 0054 +232 +174 296026 027 027 003 00

200630 2202N 08658W 9775 00250 0056 +230 +171 292028 029 028 002 03

200700 2201N 08659W 9758 00265 0058 +235 +169 280028 029 027 002 00

200730 2200N 08701W 9796 00232 0058 +246 +168 278027 028 028 002 00

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Center found this time, looks to be about 1001mb

195800 2207N 08701W 9746 00276 0058 +231 +165 321013 014 017 003 00

195830 2207N 08659W 9744 00276 0056 +225 +166 332018 021 023 002 00

195900 2207N 08657W 9720 00293 0051 +225 +165 351019 020 022 002 00

195930 2207N 08656W 9728 00278 0041 +242 +163 338023 024 023 000 00

200000 2207N 08654W 9712 00283 0029 +250 +162 334027 029 025 001 00

200030 2207N 08652W 9695 00288 0018 +248 +164 337019 024 021 002 00

200100 2208N 08651W 9742 00245 0015 +250 +168 358008 012 008 002 00

200130 2208N 08649W 9778 00203 0009 +241 +172 084007 009 007 001 03

200200 2208N 08647W 9777 00209 0011 +238 +175 187016 023 005 001 03

200230 2208N 08647W 9777 00209 0017 +236 +177 214026 030 029 002 03

200300 2206N 08649W 9775 00211 0014 +237 +180 229022 025 035 001 00

200330 2206N 08650W 9760 00228 0018 +235 +180 262024 026 040 002 03

200400 2205N 08651W 9765 00228 0026 +241 +180 284032 034 037 002 00

200430 2204N 08653W 9785 00218 0034 +233 +179 283032 032 035 003 03

200500 2204N 08654W 9764 00245 0041 +226 +179 292032 035 034 001 00

200530 2203N 08655W 9766 00245 0046 +229 +177 296029 030 031 002 00

200600 2202N 08657W 9772 00249 0054 +232 +174 296026 027 027 003 00

200630 2202N 08658W 9775 00250 0056 +230 +171 292028 029 028 002 03

200700 2201N 08659W 9758 00265 0058 +235 +169 280028 029 027 002 00

200730 2200N 08701W 9796 00232 0058 +246 +168 278027 028 028 002 00

I'm guesstimating that they will go with 40 KT/1001 mb at 5 PM.

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Dude, I need a magnifying glass to see that. What's the landfall point-- BRO?

It's several days out, so trying to show "accuracy" down to town level is kinda silly. But ya, somewhere around BRO is my guess.

I wouldn't be surprised, given that this is a small system, to see pretty quick strengthening at some point during its life. Shear could be a factor at times, but not enough to keep it from strengthening. And, of course, there's plenty of heat content as always in the GoM.

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Any reasoning you'd like to share with us, besides trying to crush my heart? :(

I think it's going to be stronger and slower than the global models (and tropical cyclone models) are currently forecasting... so the deeper-layer more easterly flow would probably kick in and steer it more westward.

Also, with light northerly shear ongoing, I would imagine the LLC would tend to end up a bit further south (towards the stronger convection).

If the storm races faster than I'm imagining, it's going to be further north and weaker, due to its proximity to the weakness in the ridge to its west.

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It's several days out, so trying to show "accuracy" down to town level is kinda silly. But ya, somewhere around BRO is my guess.

I wouldn't be surprised, given that this is a small system, to see pretty quick strengthening at some point during its life. Shear could be a factor at times, but not enough to keep it from strengthening. And, of course, there's plenty of heat content as always in the GoM.

Well, I wasn't asking for the exact street address of the landfall-- just the nearest population center. :D

He's an amature at graphic design.....but the kid can school anyone in statistics!! ;)

Speaking of graphic design, when's your next map coming out? You know how I look forward to 'em. :wub:

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