ATL: IRMA - Post-Tropical - Discussion

[AJC3]

958-959 mb extrapolated surface pressure. This is quite a bit lower than the 5 pm advisory of 969 mb.

What's 10MB between friends, right? (albeit the drop may be a few MB higher)
Plus winds appear to be a little on the low side, however there is much of the storm left to sample. Scratch that, 98KT SFMR winds were found.

Seriously, that goes to show just how invaluably important recon data is...

[Kingarabian]

[Aric Dunn]

of course recon will confirm.. but on satellite it appears to have sagged a little more to the SW the last hour or so.. almost to 17n already.. if it gets down to 16 to 16.5 then PR is in the crosshairs

[SouthDadeFish]

958-959 mb extrapolated surface pressure. This is quite a bit lower than the 5 pm advisory of 969 mb.

Surprised me considering its eyewall state on radar and satellite imagery.

Actually I thought that radar presentation wasn't too shabby. Much better than satellite imagery. The eyewall looks a little broken on the NW side. I wonder if this is the beginning of an intensification period. Nice timing for recon.

[OntarioEggplant]

958-959 mb extrapolated surface pressure. This is quite a bit lower than the 5 pm advisory of 969 mb.

I'm not particularly surprised. I've felt like the NHC advisory estimates have been running a bit high on pressure, but generally fine on winds.

[RL3AO]

On a side note, score one point for the Dvorak technique (and ADT).

CI# /Pressure/ Vmax
5.3 / 963.3mb/ 97.2kt

[Alyono]

SFMR of 98 kts is a legit reading

[galaxy401]

I think some people need to realize that it's quite rare to have a major hurricane that far out at sea. The open Atlantic is never really that favorable even in active seasons.

I beg to differ. It is quite normal its just the the previous years before last it was more rare.

Can you provide some specific examples? I've seen strong hurricanes near Cape Verde and other strong storms near the Caribbean islands but the open Atlantic is much less frequent. Many storms start taking off once they cross 50W. I'm sure it happens at times but not as frequent as some think.

[Alyono]

this is down at 17.4N. It's resumed a good WSW motion

[Extratropical94]

URNT15 KWBC 032141
NOAA2 0111A IRMA HDOB 15 20170903
213130 1742N 04939W 6957 03059 9910 +104 //// 131081 082 064 014 01
213200 1744N 04938W 6965 03064 9928 +101 //// 130077 079 061 013 01
213230 1746N 04937W 6962 03080 9940 +103 +102 129072 074 058 010 00
213300 1747N 04936W 6965 03088 9946 +110 +093 126070 071 052 008 00
213330 1749N 04935W 6966 03095 9956 +111 +088 125065 067 049 009 00
213400 1751N 04934W 6968 03096 9964 +109 +089 129065 068 047 009 00
213430 1753N 04933W 6967 03106 9980 +104 +084 130063 063 044 009 00
213500 1755N 04931W 6951 03134 9982 +107 +085 125058 058 042 008 00
213530 1757N 04930W 6969 03113 9987 +108 +076 123057 057 042 002 00
213600 1758N 04929W 6971 03113 9992 +106 +080 125058 058 041 002 00
213630 1800N 04928W 6966 03128 0004 +102 +081 121057 058 040 002 00
213700 1802N 04927W 6968 03129 0009 +102 +077 120056 057 039 002 00
213730 1804N 04926W 6965 03136 0019 +098 +072 122056 056 035 003 00
213800 1806N 04925W 6958 03144 0022 +097 +078 124054 055 035 003 00
213830 1808N 04924W 6956 03152 0023 +099 +074 119053 054 033 004 00
213900 1809N 04923W 6952 03160 0016 +110 +044 115060 061 030 002 00
213930 1811N 04922W 6952 03162 0017 +112 +030 118061 062 033 002 00
214000 1813N 04921W 6953 03163 0021 +110 +040 120059 059 034 002 00
214030 1815N 04920W 6952 03169 0025 +111 +036 119058 058 033 002 00
214100 1816N 04919W 6952 03171 0029 +110 +028 120058 059 033 001 00

[Kingarabian]

958-959 mb extrapolated surface pressure. This is quite a bit lower than the 5 pm advisory of 969 mb.

What's 10MB between friends, right? (albeit the drop may be a few MB higher)
Plus winds appear to be a little on the low side, however there is much of the storm left to sample.

Seriously, that goes to show just how invaluably important recon data is...

Also I want to note that Dvorak is not too far off from recon data on the ADT -- which to me is always reassuring.

CI# /Pressure/ Vmax
5.3 / 963.3mb/ 97.2kt


Final T# Adj T# Raw T#
5.0 4.8 4.8

[Kingarabian]

[HURRICANELONNY]

Little off topic but not much. Does Storm2k still have a chat room. I don't see any links to talk about Irma.

[GCANE]

Recon measured 959 mb extrapolated.

[Extratropical94]

Product: NOAA Vortex Message (URNT12 KWBC)
Transmitted: 3rd day of the month at 21:44Z
Agency: National Oceanic and Atmospheric Administration (NOAA)
Aircraft: Lockheed WP-3D Orion (Reg. Num. N42RF)
Storm Number & Year: 11 in 2017
Storm Name: Irma (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 06
A. Time of Center Fix: 3rd day of the month at 21:26:12Z
B. Center Fix Coordinates: 17°23'N 49°52'W (17.3833N 49.8667W) (View map)
B. Center Fix Location: 713 statute miles (1,148 km) to the ENE (66°) from Bridgetown, Barbados.
C. Minimum Height at Standard Level: 2,764m (9,068ft) at 700mb
D. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 79kts (~ 90.9mph)
E. Location of the Estimated Maximum Surface Wind Inbound: 11 nautical miles (13 statute miles) to the WSW (253°) of center fix
F. Maximum Flight Level Wind Inbound: From 332° at 87kts (From the NNW at ~ 100.1mph)
G. Location of Maximum Flight Level Wind Inbound: 11 nautical miles (13 statute miles) to the WSW (253°) of center fix
H. Minimum Sea Level Pressure: 961mb (28.38 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 11°C (52°F) at a pressure alt. of 3,044m (9,987ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 18°C (64°F) at a pressure alt. of 3,001m (9,846ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 12°C (54°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Open in the west, W
M. Eye Shape & Diameter: Circular with a diameter of 30 nautical miles (35 statute miles)
N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
N. Fix Level: 700mb
O. Navigational Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 1 nautical mile

Remarks Section:
Maximum Flight Level Outbound and Flight Level Wind: 96kts (~ 110.5mph) which was observed 17 nautical miles (20 statute miles) to the NNE (33°) from the flight level center at 21:30:11Z
Dropsonde Surface Wind at Center: From 185° at 11kts (From the S at 13mph)

[CrazyC83]

Based on that data, agreed with the BT intensity of 100 kt.

[NJWxHurricane]

this is down at 17.4N. It's resumed a good WSW motion

why did it go wnw like that for a little bit? and also is it possible for it to occur again?

[Aric Dunn]

this is down at 17.4N. It's resumed a good WSW motion

why did it go wnw like that for a little bit? and also is it possible for it to occur again?

well two possible options . 1. it was just internal structrual changes that often casuse wobbles. or 2. the ridge was and is still building to its north and there is often stair stepping that happens as the hurricane bumps into it.

[Extratropical94]

URNT15 KWBC 032151
NOAA2 0111A IRMA HDOB 16 20170903
214130 1818N 04918W 6951 03175 0032 +109 +044 120057 058 033 001 00
214200 1820N 04917W 6952 03175 0034 +109 +051 119056 056 034 001 00
214230 1822N 04916W 6952 03176 0040 +105 +050 119053 053 031 002 00
214300 1824N 04915W 6951 03180 0044 +105 +046 121051 052 032 002 00
214330 1825N 04914W 6949 03186 0047 +105 +051 119052 053 032 001 00
214400 1827N 04912W 6952 03181 0047 +104 +055 119052 052 034 001 00
214430 1829N 04911W 6953 03182 0052 +101 +055 119051 052 033 002 00
214500 1831N 04910W 6952 03186 0052 +105 +040 118052 052 035 001 00
214530 1832N 04909W 6952 03188 0058 +102 +038 117051 052 036 000 00
214600 1834N 04908W 6951 03189 0060 +100 +056 118049 049 035 001 00
214630 1836N 04907W 6954 03186 0057 +102 +058 118050 050 034 002 00
214700 1838N 04906W 6953 03189 0052 +107 +056 118049 049 032 003 00
214730 1839N 04905W 6953 03190 0046 +114 +052 116047 048 033 003 00
214800 1841N 04904W 6952 03194 0053 +112 +047 117045 045 034 001 00
214830 1843N 04903W 6953 03193 0060 +105 +058 118044 044 034 001 00
214900 1845N 04901W 6951 03198 0061 +106 +060 118044 045 033 002 00
214930 1846N 04900W 6952 03198 0060 +107 +057 118045 045 034 003 00
215000 1848N 04859W 6951 03200 0058 +108 +066 116044 044 033 002 00
215030 1850N 04858W 6952 03198 0061 +105 +072 114044 045 032 003 00
215100 1852N 04857W 6952 03198 0065 +103 +072 114044 044 035 003 00

[AJC3]

this is down at 17.4N. It's resumed a good WSW motion

why did it go wnw like that for a little bit? and also is it possible for it to occur again?

Maybe a bit north of due west, but it didn't look like WNW to me. In any extent, that was simply a trochoidal wobble.
I think a few Twitter posts got a little too caught up in its significance.