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Post by tornado on May 12, 2016 12:35:06 GMT -5
Earlier this week, I noticed a number of cases when airports were hit by strong wind gusts, due to thunderstorms. Some of those instances could have had more warning than was provided. The CWO at St. Louis did an excellent job with the thunderstorms yesterday! But, issues at LAWRS sites continue; so a separate thread is needed for those.
Wed 11 May 2016:
Terre Haute, Indiana:
METAR KHUF 112253Z 20008KT 9SM CLR 24/20 A3001 RMK AO2 LTG
DSNT ALQDS SLP159 T02440200
SPECI KHUF 112306Z 23017G39KT 7SM VCTS -RA SCT031 BKN060
21/14 A3004 RMK AO2 PK WND 23039/2259 LTG DSNT
ALQDS RAB00 P0000 T02060139
Instead of CLR with LTG DSNT, some mention of the CB activity moving directly toward the airport, would have been nice:
Instead, 6 minutes after the CLR/DSNT LTG, winds gusted to 39 knots.
Louisville-Bowman Field, Kentucky:
METAR KLOU 120053Z 22005KT 8SM FEW024 24/21 A3006 RMK AO2
LTG DSNT ALQDS RAE37 TSB01E24 PRESRR SLP174 P0003
T02390211
There was no mention of the line of CB/TS heading for the airfield at 0053Z, only LTG DSNT ALQDS:
6 minutes after the METAR, the airport got hit with a wind gust to 47 knots:
SPECI KLOU 120103Z 30030G47KT 10SM VCTS SQ FEW022 SCT030
SCT041 22/17 A3006 RMK AO2 PK WND 25047/0059 LTG
DSNT ALQDS T02170167
In both cases, there could have been more "lead time" for pilots and ground crews to react. For example, the CWO at St. Louis reported CB moving right towards the airport, while the storm was still more than 10 miles out:
SPECI KSTL 111812Z 09010KT 6SM HZ SCT023 BKN030 OVC250 27/21
A2992 RMK AO2 PRESFR CB DSNT SW MOV NE AND DSNT
W MOV E
SPECI KSTL 111822Z 05004KT 7SM -TSRA SCT023 BKN030CB OVC100
27/21 A2997 RMK AO2 TSB21RAB21 PRESRR VIS W 3
OCNL LTGICCG SW-NW TS SW-NW MOV E P0000
SPECI KSTL 111836Z 27027G41KT 1 1/4SM -TSRA SQ SCT023 BKN045CB
OVC100 26/22 A3001 RMK AO2 TSB21RAB21 FRQ LTGCGCCIC
ALQDS TS ALQDS MOV E P0002 $
That thunderstorm hazard was identified 9 minutes before thunder began, and 24 minutes before the gust to 41 knots. |
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Post by alstein on May 12, 2016 12:45:01 GMT -5
I wish we were allowed more discretion on distant CB/TCU remarks here, it's hard to give heads up when you see it coming because you get dinged for an error if you do.
Got no problem with our rules being the minimum standard, but we should be allowed to go above and beyond.
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Post by tornado on May 12, 2016 14:10:15 GMT -5
Agreed. I would recommend in the D version of the 7900.5, to include examples such as:
TS DSNT SW MOV NE
CB DSNT W MOV E
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Post by tornado on May 14, 2016 11:26:49 GMT -5
Fri 13 May 2016:
St. Joseph, Missouri:
This site already had wind gusts to 25 knots, under fair skies:
METAR KSTJ 131853Z 24020G25KT 10SM FEW110 27/11 A2992 RMK
AO2 PK WND 20030/1832 PRESRR SLP127 T02670111
However, off to the distance, was a line of thunderstorms:
That line of storms produced lightning within 10 miles of KSTJ, as early as 1924Z:
 
A thunderstorm was not reported by KSTJ until 2053Z:
SPECI KSTJ 131938Z 22018G44KT 1 3/4SM R35/4000VP6000FT +RA
FEW050 SCT070 OVC095 18/13 A2993 RMK AO2 PK WND
24044/1933 LTG DSNT W-NE RAB10 P0007 T01830133
SPECI KSTJ 131945Z 24011G24KT 3SM -RA SCT038 BKN070 OVC095
19/14 A2993 RMK AO2 PK WND 24044/1933 LTG DSNT
W-NE RAB10 P0007 T01890139
METAR KSTJ 131953Z 24011KT 10SM FEW036 SCT070 BKN090 19/14
A2994 RMK AO2 PK WND 24044/1933 LTG DSNT ALQDS
RAB10E53 SLP137 P0007 T01890144
METAR KSTJ 132053Z AUTO 25006KT 5SM -TSRA BKN065 OVC080 19/16
A2994 RMK AO2 LTG DSNT E-SW RAB36 TSB53 SLP138
P0002 60009 T01890156 53006
Yet, a wind gust to 44 knots, struck the airport at 1933Z. If the thunderstorm had been reported soon after the lightning strike at 1919Z,
there would have been some warning that the winds could get even stronger.
Abilene, Texas:
According to the 0352Z METAR, there weren't any hazards nearby:
METAR KABI 140352Z 16008KT 10SM CLR 23/19 A3010 RMK AO2 SLP170 T02330189
However, this was the radar map at 0350Z:
A line of thunderstorms was approaching Abilene, but that wasn't mentioned in that METAR. By the next METAR,
the weather conditions were as follows:
METAR KABI 140452Z 34015G31KT 9SM -TSRA FEW027 BKN044 OVC060
19/16 A3018 RMK AO2 PK WND 28035/0434 RAB45 TSB47
SLP198 TS W MOV SE P0000 T01890156
Note the time of the peak wind: 0434Z, to 35 knots. So the strongest wind struck the airport, before the thunderstorm was
reported at 0452Z (TS officially began at 0447Z). Lightning struck within 10 miles of KABI as early as 0418Z:
 
There could have been either VCTS reported (from ALDARS), or TS VC NW (from LAWRS). That would have given pilots
more than 10 minutes lead time of the gust to 35 knots. But that didn't happen.
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Post by hlsto2 on May 14, 2016 11:37:24 GMT -5
I wish we were allowed more discretion on distant CB/TCU remarks here, it's hard to give heads up when you see it coming because you get dinged for an error if you do. Got no problem with our rules being the minimum standard, but we should be allowed to go above and beyond. what is it you are not allowed to do? |
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Post by TCU 2U2 on May 14, 2016 12:07:39 GMT -5
I wish we were allowed more discretion on distant CB/TCU remarks here, it's hard to give heads up when you see it coming because you get dinged for an error if you do. Got no problem with our rules being the minimum standard, but we should be allowed to go above and beyond. what is it you are not allowed to do? While distant CB remarks do not require movement, we would never write up if one did report. Any action like this by the observer is enhancing the very limited (and poorly written) 7900.5C requirements, and is accepted by our quality control program. What exactly are you not allowed to report? .... if you don't mind posting that is. |
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Post by alstein on May 14, 2016 13:03:14 GMT -5
distant cb movement.
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Post by hlsto2 on May 14, 2016 16:42:53 GMT -5
so...if you have a severe CB 40 NW of the AP...moving SE toward the AP at 40 mph...you can't give movement until it is within 10 miles and 15 minutes of the AP? on my 3-11p shift on the 11th..I reported dsnt CB SW-NW moving SE beginning at 0053Z...starteed TS at 0314Z...and had a peak wind of 44 knots at 0340. this gave the AP nearly 3 hours lead time. but I would be in trouble if I did this with your contractor?
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Post by tornado on May 15, 2016 9:19:26 GMT -5
so...if you have a severe CB 40 NW of the AP...moving SE toward the AP at 40 mph...you can't give movement until it is within 10 miles and 15 minutes of the AP? on my 3-11p shift on the 11th..I reported dsnt CB SW-NW moving SE beginning at 0053Z...starteed TS at 0314Z...and had a peak wind of 44 knots at 0340. this gave the AP nearly 3 hours lead time. but I would be in trouble if I did this with your contractor? DSNT CB movement, would have helped in this case! Sat 14 May 2016:
Idaho Falls, Idaho:METAR KIDA 142253Z 35003KT 10SM SCT110 24/04 A2982 RMK AO2 SLP064 VIRGA SHRA DSNT ALQDS MOV N T02440039 METAR KIDA 142353Z 21040G51KT 5SM -RA BLDU BKN090 21/04 A2983 RMK AO2 PK WND 21051/2353 RAB52 SLP073 VIRGA SHRA OVHD ALQDS MOV NE P0000 60000 T02110039 10250 20200 55011 SPECI KIDA 142357Z 21040G51KT 5SM -TSRA BLDU BKN095 19/06 A2986 RMK AO2 PK WND 22050/2355 WSHFT 2341 TSB57 PRESRR P0000 T01940056 In this case, the strong wind struck before the thunderstorm. I looked at lightning data, and there wasn't any cloud-to-ground lightning within 10 miles. But at 2253Z, something like CB DSNT SE-SW could have been reported, according to radar:  There were 2 level 3 (or greater) cells, just beyond 10 miles, certainly within 15 miles. A remark of CB DSNT SE-SW MOV N would have provided much more lead time of the hazard. DSNT VIRGA and SHRA may not have been taken seriously by pilots. The gust to 51 knots was an apparent surprise, exceeding what was in the TAF: TAF KIDA 142332Z 1500/1524 24015G35KT 6SM BLDU VCTS SCT050CB SCT110 FM150100 22009KT P6SM VCSH SCT060 FM151300 21011KT P6SM -SHRA BKN025 OVC040 FM151800 21015G25KT P6SM VCSH SCT025 BKN040 Movement should definitely be allowed with DSNT CB! |
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Post by alstein on May 15, 2016 15:56:41 GMT -5
I'll say this- if there's an obvious CB with anvil that's clearly visible and heading towards the airport, I'd put it in and argue it later. I seriously doubt I would get in real trouble for that.
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Post by tornado on May 31, 2016 8:36:58 GMT -5
Hobbs, New Mexico:
METAR KHOB 310155Z AUTO 21008KT 10SM VCTS CLR 25/12 A2994
RMK AO2 LTG DSNT S AND SW
ASOS recorded VCTS CLR, with only 8 knots of wind. That must have been a weak thunderstorm, yes?
No:
METAR KHOB 310215Z AUTO 25035G52KT 9SM SCT070 20/13 A2999
RMK AO2 LTG DSNT E AND S
That strong wind gust was from 250°, so looking in that direction, one can see that the core of the thunderstorm, was beyond 10 miles:
 
It seems ALDARS didn't include LTG DSNT SW-W, because most of that lightning occurred before 0200Z. There were 3 cloud-to-ground lightning strikes about 11-15 miles to the SW, between 0227-0231Z; so the thunderstorm hadn't dissipated yet. This is a case when a thunderstorm gust front, struck a small airport, when the cell was beyond 10 miles away. That's why, at our nation's largest airports, CB DSNT remarks are important! Just a bit of LTGIC at the Hobbs Airport (likely), would have qualified that as a severe thunderstorm.
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Post by tornado on Jun 1, 2016 14:48:17 GMT -5
Athens, Georgia, Tue 31 May 2016:
METAR KAHN 312251Z 18005KT 10SM CLR 31/18 A2989 RMK AO2 LTG
DSNT SE SLP115 T03060183
How accurate was that METAR? To look at it, ALDARS had identified a hazard: lightning to the distant southeast.
While that was true, were the skies really clear? No:
That was the radar map at 2245Z. That gave LAWRS plenty of time to augment the sky condition from CLR to something else,
and add in CB remarks. but that didn't happen. The level 4 cell to the north wasn't mentioned. By 2255Z, it had grown to a level 5 cell:
ALDARS began a thunderstorm at 2322Z, and ASOS transmitted the SPECI to begin the TS 6 minutes later:
SPECI KAHN 312328Z 01011G24KT 330V060 10SM TS BKN065 BKN100
29/19 A2992 RMK AO2 LTG DSNT SE TSB22 T02890189
So was it the distant lightning that eventually resulted in the thunderstorm at KAHN? No:
The winds increased from 18005KT to 01011G24KT. The point here is that LAWRS trusted ALDARS to correctly assess where the thunderstorm hazard was; and trusted ASOS to report clouds from the thunderstorm. In this case, neither ALDARS, ASOS, nor LAWRS got the 2251Z METAR to be as accurate as it could have been. A CWO would likely have added CB N STNRY or something similar. Or, LTGIC may have produced audible thunder by 2251Z, to an observer outside. |
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Post by tornado on Jun 11, 2016 9:34:15 GMT -5
Minot, North Dakota, 9 Jun 2016:
METAR KMOT 100254Z 00000KT 10SM CLR 30/17 A2957 RMK AO2 SLP999
T03000172 56006
SPECI KMOT 100337Z 00000KT 10SM VCTS CLR 26/18 A2956 RMK
AO2 LTG DSNT SW-N T02610178
Hopefully, there aren't still pilots that believe that VCTS CLR = weak thunderstorm, even when the VCTS CLR has calm winds. Within minutes, this can- and did- happen:
SPECI KMOT 100346Z 29035G50KT 10SM TS SQ CLR 26/18 A2963
RMK AO2 PK WND 30050/0346 LTG DSNT SW-N TSB40 PRESRR T02610178
METAR KMOT 100354Z 32042G55KT 5SM -TSRA SQ FEW041 SCT080 23/16 A2964
RMK AO2 PK WND 31055/0354 LTG DSNT SW-N RAB48 TSB40 PRESRR SLP026 P0000 T02280161
Of course, it was only "clear", because the clouds hadn't been detected by ASOS, and LAWRS left it that way. That was even with a level 6 cell moving right towards Minot International Airport:
 
Hopefully, pilots weren't relying on radar, to detect where the strongest winds were within that storm:
As can be seen by the radar map above, taken 1 minute before the wind gust to 50 knots; the heaviest rain echo,
did not match the position of the gust front. At the time of that radar map, calm winds were still on the ATIS.
Every thunderstorm must be taken seriously!
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Post by tornado on Jun 29, 2016 13:05:57 GMT -5
Clinton-Sherman Airport, Oklahoma, Tue 28 Jun 2016:
At 2350Z on June 28th, this was the radar display from west-central Oklahoma, where Clinton-Sherman Airport is located:
While ALDARS reported LTG DSNT ALQDS, clear skies were recorded on the METAR 3 minutes later:
METAR KCSM 282353Z 10010KT 10SM CLR 34/19 A3008 RMK AO2 LTG
DSNT ALQDS SLP160 T03390194 10344 20317 55006
Winds were 10010KT. Did the LTG DSNT ALQDS make it onto the ATIS? We don’t know. Within a half hour of
the 2353Z METAR, this happened:
SPECI KCSM 290021Z 02041G62KT 5SM VCTS -RA SQ FEW033 SCT060
23/17 A3015 RMK AO2 PK WND 01062/0018 LTG DSNT
ALQDS RAB21 PRESRR P0000 T02330172
The radar displays at 0015Z and 0020Z, showed that the core of the thunderstorms had not reached the airport:
 
Relying solely on radar to detect the thunderstorm hazards, is unsafe. In this case, the thunderstorm gust front was well out ahead of the thunderstorm, and produced a gust to 62 knots at 0018Z. The cell that produced the gust was to the north, not E-SE, based on the wind direction of 010° . Level 5-6 rain echoes were in that direction.
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Post by tornado on Jul 5, 2016 15:10:03 GMT -5
Fargo, North Dakota, Mon 4 Jul 2016:
Hector International Airport (KFAR) in Fargo had a seemingly quiet weather report at 7:53 p.m. (0053Z):
METAR KFAR 050053Z 19009KT 10SM CLR 29/17 A2963 RMK AO2 SLP029
T02940167
However, this was the radar at 0050Z:
One can see a level 6 cell about 30 miles due west of the airport. It didn't take long for that cell to arrive at Hector Field:
SPECI KFAR 050129Z 27038G48KT 2SM +RA SQ SCT041 BKN085 OVC110
23/19 A2970 RMK AO2 PK WND 27048/0128 RAB15 PRESRR
P0000 T02280189
By 0128Z, the thunderstorm had produced a gust (squall) to 48 knots! Heavy rain was falling, reducing the airfield to IFR conditions.
Looking to the southwest, lightning had struck within 5 miles, as early as 0114Z:
 
The bolts at 0114Z and 0117Z, were about 4 miles from the airport. Yet, not only was there no thunderstorm reported on the 0129Z SPECI, there was no thunderstorm reported at all that hour:
SPECI KFAR 050132Z 28033G48KT 3/4SM +RA BR SQ SCT023 BKN065
OVC110 21/19 A2971 RMK AO2 PK WND 27048/0128 RAB15
PRESRR P0000 T02110194
SPECI KFAR 050141Z 32023G44KT 2SM +RA BR SCT030 BKN070 OVC110
21/18 A2971 RMK AO2 PK WND 27048/0128 VIS 3/4V4
RAB15 P0015 T02060183
SPECI KFAR 050144Z 33021G41KT 3SM +RA BR FEW032 BKN070 OVC110
21/18 A2971 RMK AO2 PK WND 27048/0128 WSHFT 0130
RAB15 P0019 T02060183
METAR KFAR 050153Z 34015KT 4SM +RA SCT041 BKN070 OVC080 21/18
A2969 RMK AO2 PK WND 27048/0128 WSHFT 0130 RAB15
SLP050 P0021 T02110178
Winds increased from WSW at 8 m.p.h. at 8:15 p.m., to W at 44 gusting to 55 m.p.h. at 8:29 p.m.:
Not only was that an unreported thunderstorm, which barely missed severe criteria; it must have been
moving at about 50 m.p.h., and so surprised some in the Fargo area. The situation occurred not long
before dark, so many residents were preparing to enjoy fireworks shows. Channel 11 reported parts
of North Dakota were hammered with >80 m.p.h. winds:
4th of July Storm Hammers State
A report of CB DSNT W MOV E would have given users on the ground at and around KFAR, more time to
prepare for the storm. By the way, the same convective system, slammed the Minneapolis-St. Paul area about 20 hours later: Minneapolis-Crystal:SPECI KMIC 052241Z 27041G52KT 3/4SM +TSRA FEW019 BKN039 BKN060 20/17 A2970 RMK AO2 PK WND 27052/2240 LTG DSNT ALQDS RAE13B27 TSB24 P0017 T02000172 Minneapolis-Flying Cloud Muni:SPECI KFCM 052256Z 34040G53KT 10SM -TSRA SQ BKN036 OVC046 22/17 A2970 RMK AO2 PK WND 35053/2255 LTG DSNT W-NE TSB55 P0002 T02170172 SPECI KFCM 060016Z 33025G52KT 280V010 3/4SM +TSRA SQ FEW019 BKN028 OVC070 21/18 A2976 RMK AO2 PK WND 28052/0014 WSHFT 0002 LTG DSNT ALQDS PRESRR P0045 T02110183 St. Paul Downtown-Holman Field:SPECI KSTP 052332Z 01033G58KT 1 1/2SM +TSRA BR SQ FEW011 BKN020 OVC042 20/19 A2970 RMK AO2 PK WND 36058/2332 LTG DSNT ALQDS RAB08 TSB02 PRESFR P0051 T02000189 In the case of Flying Cloud Municipal Airport, thunderstorms more than an hour apart, both met severe criteria!The MCC (Mesoscale Convective Complex) continued SE: Cedar Rapids, Iowa:SPECI KCID 060736Z AUTO 30037G54KT 1 1/2SM TS BR SQ OVC016 22/21 A2982 RMK AO2 PK WND 31054/0735 LTG DSNT ALQDS TSE06B16 PRESRR T02170211 La Crosse, Wisconsin:SPECI KLSE 060300Z AUTO 29035G59KT 2 1/2SM TSRA SQ SCT029 SCT075 BKN100 23/20 A2978 RMK AO2 PK WND 26059/0258 WSHFT 0246 LTG DSNT ALQDS TSB00 PRESRR P0000 T02330200 |
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