ATL: FIONA - Post-Tropical - Discussion

[skyline385]

Looking a bit warped (possibly tilted) in recent frames

[Iceresistance]

:uarrow: That's a pretty strong NW quadrant as that convection is rotating around, some of the SFMR winds might have been rain contaminated, pressure seems to be holding steady, maybe a mb drop.

Extrapolated pressure from NOAA2 fell to 987.8 MB as the lowest.

However, AF303's lowest extrapolated pressure is 985 MB.

[NDG]

I take it back, it looks like pressure is beginning to fall again, around a couple of mb lower from the last pass.

123300 1711N 06608W 6970 03055 9882 +143 +081 124020 023 019 000 03

[NDG]

Ooops, I missed this one, lol.

123830 1703N 06622W 6964 03047 9850 +163 +063 267038 041 /// /// 03

[wxman57]

I just don't think those SFMR winds accurately reflect true surface winds. Plane passed just north of St. Croix over water 4000 meters deep (no shoaling) and reported steady SFMR of 45-50 kts. St. Croix never reported any wind over 28 kts. Airport is nearly on the water on the south side of the island with an onshore wind. Strongest wind at St. Croix overnight were 33 gusting 48 kts. The NHC may well call it a hurricane before it passes St. Croix, but don't expect anything near hurricane strength sustained wind there. San Juan winds currently 18 gusting 29 kts. I know TJSJ is on the north side of the island, but the NHC advisory has TS winds extending 120nm to the north of the storm, which is well north of TJSJ.

TJSJ 181156Z 09018G29KT 4SM -RA BR SCT028 SCT050 BKN075 26/24 A2978 RMK AO2 PK WND 09029/1150

[kevin]

New recon pass just measured 985.0 mbar and the other plane measured 70 kt FL winds.

[Cachondo23]

Take note that recon just passed by St. Croix and reported 40kt SFMR. St. Croix has not reported a wind above 20 kts all evening. I've never trusted SFMR winds. They calibrate the instrument in clear air. Looking like cycloneye in San Juan won't even see any TS sustained wind. Lots of rain possible tomorrow, though, and even moderate TS winds will knock most of the power out.

Here in San Juan we have had sustained TS winds.

[tolakram]

[NDG]

I just don't think those SFMR winds accurately reflect true surface winds. Plane passed just north of St. Croix over water 4000 meters deep (no shoaling) and reported steady SFMR of 45-50 kts. St. Croix never reported any wind over 28 kts. Airport is nearly on the water on the south side of the island with an onshore wind. Strongest wind at St. Croix overnight were 33 gusting 48 kts. The NHC may well call it a hurricane before it passes St. Croix, but don't expect anything near hurricane strength sustained wind there. San Juan winds currently 18 gusting 29 kts. I know TJSJ is on the north side of the island, but the NHC advisory has TS winds extending 120nm to the north of the storm, which is well north of TJSJ.

TJSJ 181156Z 09018G29KT 4SM -RA BR SCT028 SCT050 BKN075 26/24 A2978 RMK AO2 PK WND 09029/1150

San Juan's airport just had a wind gust of 55 mph, sustained near TS force, 15 minutes ago

Sep 18, 8:35 am 79 75 89 E 39G55

https://www.weather.gov/wrh/timeseries? ... J&hours=72

[Iceresistance]

San Juan Radar


https://s4.gifyu.com/images/TJUA_loop.gif

[NDG]

That burst of convection from above.

[NDG]

I guess the dropsonde didn't catch the SLP at splashdown.

000
URNT12 KNHC 181307
VORTEX DATA MESSAGE AL072022
A. 18/12:37:40Z
B. 17.11 deg N 066.36 deg W
C. 700 mb 2999 m
D. EXTRAP 989 mb
E. NA
F. OPEN S
G. C40
H. 61 kt
I. 336 deg 15 nm 12:22:30Z
J. 064 deg 65 kt
K. 336 deg 15 nm 12:22:30Z
L. 39 kt
M. 137 deg 33 nm 12:47:00Z
N. 242 deg 53 kt
O. 137 deg 35 nm 12:47:30Z
P. 8 C / 3042 m
Q. 18 C / 3043 m
R. 9 C / NA
S. 12345 / 7
T. 0.02 / 2 nm
U. AF303 1107A FIONA OB 09
MAX FL WIND 66 KT 046 / 81 NM 11:18:00Z
SLP EXTRAP FROM 700 MB
;

[NDG]

NE quadrant now getting stronger.

249
URNT15 KWBC 181316
NOAA2 1007A FIONA HDOB 29 20220918
130630 1750N 06545W 7505 02520 0036 +129 +134 127050 053 051 002 01
130700 1748N 06545W 7511 02508 0036 +125 +137 132053 054 051 002 01
130730 1747N 06546W 7507 02511 0034 +126 +140 130057 058 049 002 01
130800 1745N 06547W 7509 02506 0030 +127 +141 129057 058 047 002 01
130830 1743N 06548W 7507 02508 0029 +125 +139 125057 062 048 007 01
130900 1742N 06549W 7505 02508 0025 +126 +142 127061 064 047 008 01
130930 1740N 06550W 7509 02496 0016 +128 +143 130061 065 050 016 01
131000 1738N 06550W 7505 02497 0013 +129 +150 126063 063 052 024 01
131030 1737N 06551W 7506 02489 0005 +131 +157 127064 065 059 032 01
131100 1735N 06552W 7503 02493 0008 +126 +161 127064 069 059 033 01
131130 1733N 06553W 7493 02500 0007 +126 +160 135062 066 054 050 01
131200 1732N 06554W 7505 02484 9999 +128 +159 141062 062 062 035 01
131230 1730N 06554W 7506 02479 9992 +129 +155 147061 063 062 016 01
131300 1729N 06555W 7506 02477 9984 +133 +150 157058 062 062 008 01
131330 1727N 06556W 7509 02469 9984 +130 +145 162056 059 060 002 01
131400 1726N 06557W 7503 02476 9988 +125 +144 161058 058 060 002 01
131430 1724N 06558W 7517 02456 9981 +129 +142 159055 057 058 000 01
131500 1723N 06600W 7509 02461 9974 +131 +148 157054 055 052 000 01
131530 1723N 06602W 7511 02454 9955 +143 +151 153052 054 052 000 01
131600 1722N 06604W 7511 02449 9938 +155 +144 155052 052 053 000 00

[wxman57]

Take note that recon just passed by St. Croix and reported 40kt SFMR. St. Croix has not reported a wind above 20 kts all evening. I've never trusted SFMR winds. They calibrate the instrument in clear air. Looking like cycloneye in San Juan won't even see any TS sustained wind. Lots of rain possible tomorrow, though, and even moderate TS winds will knock most of the power out.

Here in San Juan we have had sustained TS winds.

That's not what the official observations at the airport indicate. I see a gust to 49 kts though. I'm not sure if the airport would report a special between hourly obs to report higher sustained wind.

TJSJ 181256Z 09020G33KT 4SM -RA BR SCT023 SCT080 OVC110 25/23 A2980 RMK AO2 PK WND 09049/1235 SLP091 T02500233 PNO
TJSJ 181156Z 09018G29KT 4SM -RA BR SCT028 SCT050 BKN075 26/24 A2978 RMK AO2 PK WND 09029/1150 SLP084 6//// 7//// T02560244 10278 20244 58001 PNO
TJSJ 181056Z 08021G30KT 4SM -RA BR SCT028 BKN050 BKN075 26/24 A2979 RMK AO2 PK WND 08030/1053 SLP088 T02560239 PNO

[IsabelaWeather]

Take note that recon just passed by St. Croix and reported 40kt SFMR. St. Croix has not reported a wind above 20 kts all evening. I've never trusted SFMR winds. They calibrate the instrument in clear air. Looking like cycloneye in San Juan won't even see any TS sustained wind. Lots of rain possible tomorrow, though, and even moderate TS winds will knock most of the power out.

Here in San Juan we have had sustained TS winds.

Yeah its getting much windier here in the NW, just had a gust to 41 and 1 min sustained to 32

[IsabelaWeather]

Looking a bit warped (possibly tilted) in recent frames

https://uploads.tapatalk-cdn.com/20220918/a70ffc8953a38ee8cd477017a8589798.gif

That just looks like a meso vort to me. Its been rotating around the eyewall

[kevin]

NE quadrant now getting stronger.

249
URNT15 KWBC 181316
NOAA2 1007A FIONA HDOB 29 20220918
130630 1750N 06545W 7505 02520 0036 +129 +134 127050 053 051 002 01
130700 1748N 06545W 7511 02508 0036 +125 +137 132053 054 051 002 01
130730 1747N 06546W 7507 02511 0034 +126 +140 130057 058 049 002 01
130800 1745N 06547W 7509 02506 0030 +127 +141 129057 058 047 002 01
130830 1743N 06548W 7507 02508 0029 +125 +139 125057 062 048 007 01
130900 1742N 06549W 7505 02508 0025 +126 +142 127061 064 047 008 01
130930 1740N 06550W 7509 02496 0016 +128 +143 130061 065 050 016 01
131000 1738N 06550W 7505 02497 0013 +129 +150 126063 063 052 024 01
131030 1737N 06551W 7506 02489 0005 +131 +157 127064 065 059 032 01
131100 1735N 06552W 7503 02493 0008 +126 +161 127064 069 059 033 01
131130 1733N 06553W 7493 02500 0007 +126 +160 135062 066 054 050 01
131200 1732N 06554W 7505 02484 9999 +128 +159 141062 062 062 035 01
131230 1730N 06554W 7506 02479 9992 +129 +155 147061 063 062 016 01
131300 1729N 06555W 7506 02477 9984 +133 +150 157058 062 062 008 01
131330 1727N 06556W 7509 02469 9984 +130 +145 162056 059 060 002 01
131400 1726N 06557W 7503 02476 9988 +125 +144 161058 058 060 002 01
131430 1724N 06558W 7517 02456 9981 +129 +142 159055 057 058 000 01
131500 1723N 06600W 7509 02461 9974 +131 +148 157054 055 052 000 01
131530 1723N 06602W 7511 02454 9955 +143 +151 153052 054 052 000 01
131600 1722N 06604W 7511 02449 9938 +155 +144 155052 052 053 000 00

69 kt FL winds and 62 kt SFMR. Accounting for 10% undersampling could be enough to support a 65 kt cat 1, but since we have 2 planes making many passes I'm not sure whether taking normal undersampling percentages is best here. In any case Fiona is clearly intensifying, the passes from 2 hours ago could barely find 60+ kt FL winds and now we see quite large areas in the NE quadrant above that value.

[tolakram]

saved loop

[aspen]

Extrapolated pressure is down to 985.4mb on this center pass from NOAA2. With this pressure drop, the ~70 kt FL winds, and 60-65 kt SFMR, there’s pretty good evidence that Fiona is now a hurricane.

[tolakram]

saved loop