ATL: TROPICAL STORM BILL (03L)

[HURAKAN]

[cheezyWXguy]

The convection hasn't really been that strong with Bill for a while now but the structure is still pretty impressive I have to admit, even if it is now a category-3.

Convection not being too strong is something that is seen often with storms climbing in latitude. Remember Bertha last year? That was said to have briefly reached cat 4 status, and there was NEVER a solid ring of red around its core. The structure actually looks better to me than it did when I went to bed last night (2 central), although it doesnt really surprise me that it has since weakened.

[drezee]

12z GFS at 60 hours:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_060l.gif

still significantly to the right of the 6z

left of 0z, which IMO has more importance

[HURAKAN]

000
URNT15 KNHC 201604
AF304 0403A BILL HDOB 11 20090820
155430 2213N 06241W 6969 03043 9927 +100 +007 304054 055 049 007 00
155500 2215N 06239W 6963 03044 9916 +105 +008 301053 055 051 004 00
155530 2216N 06238W 6968 03031 9915 +101 +010 300052 052 050 005 00
155600 2218N 06237W 6971 03026 9906 +103 +014 300053 053 049 005 00
155630 2219N 06235W 6974 03015 9905 +098 +018 300051 053 051 007 00
155700 2221N 06234W 6969 03014 9906 +090 +018 298054 055 054 007 00
155730 2222N 06233W 6972 02999 9883 +102 +016 298053 053 055 005 00
155800 2224N 06231W 6967 02997 9879 +095 +014 296054 054 054 006 00
155830 2225N 06230W 6963 02992 9866 +096 +014 297056 058 055 006 00
155900 2227N 06229W 6967 02973 9843 +104 +016 294061 062 057 005 00
155930 2228N 06227W 6967 02960 9821 +109 +019 292062 064 059 005 00
160000 2230N 06226W 6969 02942 9794 +121 +023 291067 069 061 005 00
160030 2231N 06225W 6962 02942 9770 +130 +027 295071 073 061 005 00
160100 2233N 06223W 6974 02909 9744 +138 +031 295075 077 064 004 00
160130 2234N 06222W 6967 02903 9742 +122 +035 294073 076 067 007 00
160200 2236N 06221W 6966 02881 9720 +121 +035 291074 075 066 007 00
160230 2237N 06219W 6966 02858 9686 +127 +031 287076 077 070 006 00
160300 2239N 06218W 6961 02834 9652 +130 +028 290081 082 072 005 00
160330 2241N 06216W 6964 02813 9610 +147 +028 294081 084 071 005 03
160400 2242N 06216W 6961 02796 9572 +160 +031 302070 079 069 005 03
$$
;

[HURAKAN]

[wxman57]

You're not getting nervous, are you? I just calculated 3 and 12 hr movement using GARP and got a steady 305 deg heading at 17 kts for 12 hours. Same thing as if I used a 3 hr movement. I don't see any evidence of a 290-295 deg movement for any period of time. There are a few satellite images where the eye is partially covered, which could make it look like the direction changed.

Bill sure does like those jogs to the west alot. I know that NHC goes by 12 hours. But this morning he has been going about 290-295 This may be do to his little weakening. LOL from a 4 down to a 3. But that could be alot to someone that would be looking at him come their way. But he is not at this time frame.
How much more west will Bill go?It seem every up date it is a little more to the west. They keep going they will run out of water here.LOL. Now does the trough stay strong or does it weaken as time goes by. Will he catch the train up to the North? I think NHC has done a good job. It is hard to pin down where this storms will go. It is all about timing. It has been 10 years since we here around Wilm that we had a hurricane. I hope it will be many more. Floyd was the last. Yes we had a few TD or TS but that is it.
Any hows this has been a good Storm to watch and learn on. Who knows maybe he has some tricks up his sleeve. He has done good so far. All the Bill's I know are sneaky and bad.LOL

[USTropics]

A few years ago a promet on this board discussed how the 0z and 12z runs were more reliable then the 6z and 18z runs based on the amount of data input. I'm not sure if this is true for all models and hopefully someone can go more in depth on this.

[deltadog03]

http://www.atmos.washington.edu/~ovens/ ... nhanced+12

Great WV loop. (big file)

[btangy]

8/20/09 12Z GFS: GFS has slight higher heights to the N of Bill in the short term and moves the upper level low forming NE of the Bahamas quicker to the SW in line with the trend from previous runs. Result is a short term motion that is a hair left of the 00Z GFS but not as far left as the 06Z GFS.

GFS continues to trend more amplified with the trough, especially the SW side of it, and is a touch less progressive. Combined with the initial track differences in the short term, the resulting track as Bill begins to accelerate is slightly left and a bit slower at 72 hours but with little sensible difference for Nova Scotia.

With the synoptic surveillance mission later today, the 00Z runs tonight should give a better indication of the ridge weakness to the N of Bill in the short term, though I'd be surprised if there are significant differences.

[wxman57]

Here's a higher-res map showing the 12Z GFS forecast for 15Z Sunday. I Measured 155nm from Cape Cod. That would be close enough for TS winds to just barely brush the Cape.

[deltadog03]

That upper low to his NW right now is getting pushed back pretty good by bill. I would guess that it should continue to get pushed away from his outflow.

[HURAKAN]

000
URNT15 KNHC 201614
AF304 0403A BILL HDOB 12 20090820
160430 2244N 06215W 6975 02747 9550 +157 +037 297053 057 063 006 00
160500 2245N 06214W 6970 02732 9521 +165 +041 291043 046 045 004 00
160530 2247N 06213W 6963 02734 9519 +154 +044 282028 033 033 004 03
160600 2249N 06213W 6976 02707 9518 +148 +046 284017 020 028 004 03
160630 2251N 06212W 6967 02713 9518 +139 +047 250003 007 026 003 00
160700 2253N 06212W 6973 02706 9522 +135 +046 150004 005 021 004 00
160730 2254N 06211W 6962 02717 9520 +134 +044 141009 011 022 004 00
160800 2256N 06211W 6973 02711 9520 +139 +043 134012 013 022 004 03
160830 2257N 06209W 6965 02711 9518 +135 +042 140019 020 021 004 00
160900 2259N 06208W 6965 02710 9515 +136 +041 143021 022 023 004 00
160930 2300N 06206W 6965 02712 9513 +138 +041 140024 027 025 004 00
161000 2301N 06205W 6967 02706 9512 +141 +040 140032 035 037 007 00
161030 2302N 06203W 6972 02705 9518 +138 +040 138041 044 044 005 00
161100 2303N 06202W 6963 02718 9517 +146 +042 138051 053 057 008 00
161130 2305N 06201W 6980 02713 9535 +141 +044 139065 070 080 011 00
161200 2306N 06159W 6962 02747 9553 +134 +044 142080 083 095 005 00
161230 2307N 06158W 6969 02755 9578 +126 +042 143089 094 099 005 00
161300 2308N 06157W 6962 02778 9612 +115 +038 149110 121 101 010 00
161330 2309N 06155W 6984 02777 9664 +088 +031 143129 132 090 044 00
161400 2310N 06154W 6955 02832 9696 +082 +018 139130 133 091 041 00
$$
;

Extra: 951 mb
FL: 133 knots

[wxman57]

Here's a map with the 00Z GFS 15Z Sunday position (Purple lines) and 12Z GFS forecast for the same time (yellow isobars). The latest GFS is a tad slower and slightly left of 00Z.

[Ptarmigan]

Bill has a central pressure of 951 mb with 120 mph winds and hurricane force winds extending up to 105 miles, while TS winds are up to 260 miles. Ike when it made landfall had a central pressure of 952 mb with 110 mph winds, hurricane force winds extending up to 125 miles and TS winds of 260 miles. I wonder why that happens. Is the ambient pressure higher for Bill? I know Ike at one point had TS winds up to 275 miles.

[HURAKAN]

000
URNT15 KNHC 201624
AF304 0403A BILL HDOB 13 20090820
161430 2311N 06153W 6987 02812 9724 +076 +007 140133 135 090 038 00
161500 2312N 06152W 6962 02867 9749 +074 +001 138132 132 087 033 00
161530 2313N 06151W 6970 02875 9774 +074 -005 140129 131 084 023 00
161600 2314N 06150W 6964 02902 9795 +075 -007 139119 122 086 018 00
161630 2315N 06149W 6967 02917 9801 +085 -008 140117 120 078 014 00
161700 2316N 06147W 6971 02924 9811 +089 -008 144117 119 079 012 00
161730 2318N 06146W 6963 02947 9825 +092 -006 142115 116 075 009 00
161800 2319N 06145W 6968 02952 9836 +095 -003 142109 112 074 009 00
161830 2320N 06144W 6967 02969 9845 +097 -000 141104 105 071 011 00
161900 2321N 06142W 6964 02981 9855 +097 +001 142105 105 072 011 00
161930 2322N 06141W 6967 02988 9876 +088 +002 144106 106 071 013 00
162000 2323N 06140W 6967 02997 9886 +088 +003 144103 104 068 011 00
162030 2324N 06138W 6966 03005 9900 +084 +003 144102 103 066 014 00
162100 2326N 06137W 6968 03004 9908 +084 +003 145102 103 066 013 00
162130 2327N 06136W 6967 03019 9923 +080 +002 144103 103 064 013 00
162200 2328N 06134W 6966 03026 9925 +083 +002 145103 103 063 010 00
162230 2329N 06133W 6967 03031 9924 +090 +002 145102 102 063 007 00
162300 2330N 06132W 6969 03034 9927 +095 +002 145101 101 063 007 00
162330 2331N 06130W 6965 03049 9936 +092 +004 146099 099 062 008 00
162400 2332N 06129W 6968 03045 9943 +090 +006 147097 098 061 008 00
$$
;

FL: 135 knots

[x-y-no]

Thanks wxman57, I was attempting to do that by the "blink test" method - it's clearer with an overlay.

If it doesn't go much further west than that, the Cape should be fine. The lower Cape may see some TS conditions, but that area is well equipped for handling that. The upper Cape is less so.

[HURAKAN]

Continues to look great

[KWT]

However I believe the 12z is to the right of the 06z Wxman57. Still Nova Scotia seems to be in the path of the storm regardless of what run turns out to be right. Needs to be watched very closely.

[wxman57]

Bill has a central pressure of 951 mb with 120 mph winds and hurricane force winds extending up to 105 miles, while TS winds are up to 260 miles. Ike when it made landfall had a central pressure of 952 mb with 110 mph winds, hurricane force winds extending up to 125 miles and TS winds of 260 miles. I wonder why that happens. Is the ambient pressure higher for Bill? I know Ike at one point had TS winds up to 275 miles.

It's a function of the pressure gradient as it relates to the wind field size. Bill is smaller than Ike, so the same central pressure will generate higher winds than Ike's more spread out wind field. That's why central pressure alone isn't a good indicator of wind speeds. Wind field size isn't accounted for.

[hurricanefloyd5]

with FL winds of 135kts we should see an upgrade back to Cat.4 again at 2pm if not sooner!!!!!!!!