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Conference Meteo Alarm Budapest 14 – 15 December 2009 1
Forecasting severe convection Forecasting severe convection Problems and some possible solutionsProblems and some possible solutions
photo: Karim Hamid
Conference Meteo Alarm Budapest 14 – 15 December 2009 2
Damage due to convection occurs over the whole year !Damage due to convection occurs over the whole year !
Conference Meteo Alarm Budapest 14 – 15 December 2009 3
A distinction must been made A distinction must been made between warm and cold between warm and cold season :season :
In warm season situation, severe In warm season situation, severe convection is highly driven by convection is highly driven by (buoyant) instability, in (buoyant) instability, in cooperationcooperation with some windshearwith some windshearIn cold season situation, severe In cold season situation, severe convection is highly driven by convection is highly driven by dynamics and windshear, in dynamics and windshear, in cooperationcooperation with some with some (buoyant) (buoyant) iinstability (sometimes even neutral)nstability (sometimes even neutral)
Conference Meteo Alarm Budapest 14 – 15 December 2009 4
Especially in cool season, damage due Especially in cool season, damage due to convection can be to convection can be underestimateunderestimate due to the (very) low instabilitydue to the (very) low instability
Some recent cases in Belgium show Some recent cases in Belgium show this…this…
Conference Meteo Alarm Budapest 14 – 15 December 2009 5
Tornado case of 01/10/2006
photo: Karel Holvoet
Conference Meteo Alarm Budapest 14 – 15 December 2009 8
Tornado case of 01/10/2006
photo: Karel HolvoetTubize
Conference Meteo Alarm Budapest 14 – 15 December 2009 9
Tornado case of 21/01/2008 Grote Brogel
photo: Karim Hamid
A survey on the spot was made to investigate the damage
Conference Meteo Alarm Budapest 14 – 15 December 2009 10
Tornado case of 05/02/2008 Dendermonde+Lier
photo: Karim Hamid
A survey on the spot was made to investigate the damage
Conference Meteo Alarm Budapest 14 – 15 December 2009 11
At the RMI, we do efforts to better forecast At the RMI, we do efforts to better forecast situation with severe convection.situation with severe convection.
This is done by an “IThis is done by an “Ingredients-Based ngredients-Based MethodologMethodology, first puted foreward by Chuck y, first puted foreward by Chuck Doswell in 1987Doswell in 1987”.”.It says that It says that if some if some atmospheric ingredients atmospheric ingredients coincidecoincide in time and place, in time and place,the risk of severe the risk of severe convection increases, convection increases, wherever on the worldwherever on the world..
Conference Meteo Alarm Budapest 14 – 15 December 2009 12
The most important ingredients are The most important ingredients are (buoyant) (buoyant) instabilityinstability, , windshearwindshear and and the the synoptic configurationsynoptic configuration..
An important point in all this is the An important point in all this is the problem of the problem of the ‘triggering’‘triggering’ of of convection’, which is not explicitly convection’, which is not explicitly assimilateassimilated in the whole storyd in the whole story..
Conference Meteo Alarm Budapest 14 – 15 December 2009 13
instability
For the instability, For the instability, we found that the we found that the LI at 700 hPa LI at 700 hPa works better in works better in cool air masses cool air masses than the than the traditional LI.traditional LI.
LI 700LI 700
LI 500LI 500
Conference Meteo Alarm Budapest 14 – 15 December 2009 14
The BRN Shear The BRN Shear could be use to could be use to disciminate disciminate between severe between severe convective convective situations and non-situations and non-severe situations.severe situations.
A median value for A median value for the BRN shear was the BRN shear was found of 22 m²sfound of 22 m²s-2-2 with no severe with no severe convection, and 80 convection, and 80 m²sm²s-2-2 with severe with severe convection !convection !
wind shear
Conference Meteo Alarm Budapest 14 – 15 December 2009 15
The Te850 can The Te850 can be use to be use to outlineoutline the the regions where regions where MCSs are very MCSs are very improbableimprobable with with a threshold a threshold value around value around 50°50°
Forecasting Mesoscale Convective Systems (MCS)
Conference Meteo Alarm Budapest 14 – 15 December 2009 16
One can outline regions where the risk on MCSc is One can outline regions where the risk on MCSc is elevatedelevated
Forecasting Mesoscale Convective Systems (MCS)
Te850Te850
Conference Meteo Alarm Budapest 14 – 15 December 2009 17
Also some synoptic archetypical Also some synoptic archetypical configurations ate made, e.g for the jetstreakconfigurations ate made, e.g for the jetstreak
(nearly) all tornado’s are formed in storms in the (nearly) all tornado’s are formed in storms in the left exitleft exit of a jetstreak of a jetstreak
(based on 211 cases)
Conference Meteo Alarm Budapest 14 – 15 December 2009 18
Also some synoptic archetypical Also some synoptic archetypical configurations ate made, e.g for the jetstreak configurations ate made, e.g for the jetstreak (isotachs 300 hPa)(isotachs 300 hPa)
A clear difference is visible between the two cases (left exit cyclonic curved jetstreak plays a key role)A clear difference is visible between the two cases (left exit cyclonic curved jetstreak plays a key role)
tornado cases (winter)tornado cases (winter) non tornado cases (winter)non tornado cases (winter)
Conference Meteo Alarm Budapest 14 – 15 December 2009 19
An attempt is made to improve some existing An attempt is made to improve some existing severe weather indices (STP, SCP, …), with an severe weather indices (STP, SCP, …), with an adaption for our region and by using the adaption for our region and by using the threshold values and best working threshold values and best working parameters, found in our research.parameters, found in our research.
Conference Meteo Alarm Budapest 14 – 15 December 2009 20
4540.
1500
2000.
²/²40.
/14
03.
/10
01.
2
5005.0
)500(CAPE
CAPE
m
MLLCL
sm
BRNshear
sm
kmshear
sm
kmshearVVVV
ZSTP
250.
1500
2000.
²/²40.
/15
03.
/12
01.
2
7001.0
)700(CAPE
CAPE
m
MLLCL
sm
BRNshear
sm
kmshear
sm
kmshearVVVV
WSTP
[If Lift Index < +1K][e850 > 45°C][shear01 8 m/s]
[If Lift Index 700 < +0.5K][e850 < 45°C][shear01 14 m/s]
model-convection
windshear humidity low levels
instability
example: iexample: improvement of the Significant Tornado mprovement of the Significant Tornado Parameter (STP)Parameter (STP), one for cool, and warm air masses, one for cool, and warm air masses
An attemp to assimilate the triggering of convection is done by inserting the vertical velocity in the model (1).
(1) Contribution to severe weather and multimodel ensemble forecasting in Belgium, PhD Thesis D. Dehenauw, 2006
warm air masses
cool air masses
Conference Meteo Alarm Budapest 14 – 15 December 2009 21
A nice example of a unexpected tornado case:A nice example of a unexpected tornado case:
The Hautmont-tornado of August 3th, 2008The Hautmont-tornado of August 3th, 2008
At least At least 66 tornadoes tornadoes were were observed on observed on that day !that day !
The tornado The tornado in Hautmont in Hautmont was the most was the most intense one..intense one..
Source: European Severe Weather Database - http://essl.org/ESWD/
Hautmont
F2
F4
F2
Conference Meteo Alarm Budapest 14 – 15 December 2009 23
The tornado of Hautmont of 03/08/’08
F4 damage F4 damage !!
Conference Meteo Alarm Budapest 14 – 15 December 2009 24
The tornado of Hautmont of 03/08/’08
A survey on the spot was made to investigate the damage: some pictures…
Photo: Karim Hamid
Conference Meteo Alarm Budapest 14 – 15 December 2009 25
The tornado of Hautmont of 03/08/’08
Photo: Karim Hamid
Conference Meteo Alarm Budapest 14 – 15 December 2009 26
The tornado of Hautmont of 03/08/’08
Photo: Karim Hamid
Conference Meteo Alarm Budapest 14 – 15 December 2009 27
The tornado of Hautmont of 03/08/’08
Photo: Karim Hamid
Conference Meteo Alarm Budapest 14 – 15 December 2009 28
The tornado of Hautmont of 03/08/’08
Photo: Karim Hamid
Conference Meteo Alarm Budapest 14 – 15 December 2009 29
The tornado of Hautmont of 03/08/’08
Photo: Karim Hamid
Conference Meteo Alarm Budapest 14 – 15 December 2009 30
The tornado of Hautmont of 03/08/’08
Photo: Karim Hamid
Conference Meteo Alarm Budapest 14 – 15 December 2009 31
DWD analysis 24z
The tornado of Hautmont of 03/08/’08
The situation was The situation was apparentlyapparently not not threateningthreatening, with only the , with only the passage of a stable frontal wave in a westerly flowpassage of a stable frontal wave in a westerly flow
Position tornado Hautmont
Conference Meteo Alarm Budapest 14 – 15 December 2009 32
The tornado of Hautmont of 03/08/’08
At upper levels, an important trough swept over Wester Europe…At upper levels, an important trough swept over Wester Europe…
Conference Meteo Alarm Budapest 14 – 15 December 2009 34
The tornado of Hautmont of 03/08/’08
Problem: ahead of the active wave, the cloud shield broke with as Problem: ahead of the active wave, the cloud shield broke with as a result warming of the boundary level and increasing instability…a result warming of the boundary level and increasing instability…
bright spells
18z
Conference Meteo Alarm Budapest 14 – 15 December 2009 35
The tornado of Hautmont of 03/08/’08
Instability was only Instability was only marginalmarginal to moderate with a CAPE around 700 to moderate with a CAPE around 700 J/kg…J/kg…
Source: KMI/D. Dehenauw
Conference Meteo Alarm Budapest 14 – 15 December 2009 36
The tornado of Hautmont of 03/08/’08
Even a larger problem: the windshear ahead of the wave was Even a larger problem: the windshear ahead of the wave was exeptional high!exeptional high!
A 0-1 km windshear near 20 A 0-1 km windshear near 20 m/s !m/s !
A 03SRH around 350 m²/s² !A 03SRH around 350 m²/s² !
Source: KMI/D. Dehenauw
Source: KMI/D. Dehenauw
Conference Meteo Alarm Budapest 14 – 15 December 2009 37
The tornado of Hautmont of 03/08/’08
It was a It was a combinationcombination of very strong forcing, of very strong forcing, exeptional high windshear (low level and exeptional high windshear (low level and deep level & storm-relative) and the deep level & storm-relative) and the precense of some instability which caused an precense of some instability which caused an exeptional violent tornado…exeptional violent tornado…
So, So, apparentlyapparently all the all the necessarynecessary ingredientsingredients were present at that place…were present at that place…
Conference Meteo Alarm Budapest 14 – 15 December 2009 38
The tornado of Hautmont of 03/08/’08
Was this situation well Was this situation well predicted ?????predicted ?????
Conference Meteo Alarm Budapest 14 – 15 December 2009 39
The tornado of Hautmont of 03/08/’08
Belgium: Belgium: orange color orange color for floodsfor floods
France: France: yellow color yellow color for floodsfor floods
Meteo alarm 18zMeteo alarm 18z
Conference Meteo Alarm Budapest 14 – 15 December 2009 40
The tornado of Hautmont of 03/08/’08
Despite the fact that the warning was valid for floods, a Despite the fact that the warning was valid for floods, a risk for risk for strong windgustsstrong windgusts was mentioned in the text at the was mentioned in the text at the RMI (RMI (based on the very high compouned parametersbased on the very high compouned parameters).).
Conference Meteo Alarm Budapest 14 – 15 December 2009 41
The tornado of Hautmont of 03/08/’08
Was this situation well Was this situation well predicted ?????predicted ?????
NO !!!!NO !!!!
……or (at least) not enoughor (at least) not enough
Conference Meteo Alarm Budapest 14 – 15 December 2009 42
The tornado of Hautmont of 03/08/’08
Was this situation Was this situation predictablepredictable
??????????
Conference Meteo Alarm Budapest 14 – 15 December 2009 43
The tornado of Hautmont of 03/08/’08
Very local things like tornadoes are Very local things like tornadoes are barelybarely predictable, because the very local situation predictable, because the very local situation just near a convective storm can’t be just near a convective storm can’t be predicted by models. Moreover, not predicted by models. Moreover, not everything is known concerning everything is known concerning tornadogenisis…tornadogenisis…
Conference Meteo Alarm Budapest 14 – 15 December 2009 44
The tornado of Hautmont of 03/08/’08
However, there were some However, there were some importantimportant signalssignals from the meso- from the meso-models:models:
Strong signalsStrong signals from the SCP, STP and original STP indices in ETA from the SCP, STP and original STP indices in ETA
Source: KMI/D. Dehenauw
Source: KMI/D. Dehenauw
Conference Meteo Alarm Budapest 14 – 15 December 2009 45
The tornado of Hautmont of 03/08/’08
- Abnormal highAbnormal high EEnergy nergy HHelicity elicity IIndexndex (EHI-black (EHI-black lines) for a lines) for a baroclinic situationbaroclinic situation
- - Very highVery high low low level SRH (colored level SRH (colored lines) up to 350 lines) up to 350 m²/s² wich is very m²/s² wich is very favorable for favorable for tornadogenesistornadogenesis
Source: KMI/D. Dehenauw
Conference Meteo Alarm Budapest 14 – 15 December 2009 46
The tornado of Hautmont of 03/08/’08
This situation This situation beautifulbeautifully ly showed the power of this showed the power of this compoundcompound indices indices
Conference Meteo Alarm Budapest 14 – 15 December 2009 47
A 2the recent example: 25-26 May A 2the recent example: 25-26 May 20092009Passage of several very destructive Mesoscale Convective Passage of several very destructive Mesoscale Convective
Systems Systems
- Passage of a strong - Passage of a strong supercellsupercell over Belgium, followed by a over Belgium, followed by a very fast very fast Squall LineSquall Line
- Important Important wind damagewind damage
-Relative widespread Relative widespread hailhail damage with stones up to damage with stones up to 12 cm12 cm in in northern France and almost northern France and almost 10 cm10 cm in Belgium in Belgium
Conference Meteo Alarm Budapest 14 – 15 December 2009 48
Hail case of 25-26/05/2009 in Belgium en N-France
Conference Meteo Alarm Budapest 14 – 15 December 2009 49
Hail case of 25-26/05/2009 in Belgium en N-France
Conference Meteo Alarm Budapest 14 – 15 December 2009 50
Hail case of 25-26/05/2009 in Belgium en N-France
Lapse rate of 19 °C between 800 hPa-600 hPa
This is 8.5 °C/km !!
Typical Elevated Mixing Layer (Spanish Plume)
Conference Meteo Alarm Budapest 14 – 15 December 2009 51
Hail case of 25-26/05/2009 in Belgium en N-France
Squall Line@ 100 km/h !
00.30z
supercell
Conference Meteo Alarm Budapest 14 – 15 December 2009 52
Hail case of 25-26/05/2009 in Belgium en N-France
23.50z
Supercell with pendant shape / hook echo
Conference Meteo Alarm Budapest 14 – 15 December 2009 53
Hail case of 25-26/05/2009 in Belgium en N-France
Hail upto 12 cm near the French border (Raillencourt-Sainte-Olle) – Source : E. Wesolak & P. Mahieu – Observatoire Français des Tornades et des Orages Violants
Conference Meteo Alarm Budapest 14 – 15 December 2009 54
Hail case of 25-26/05/2009 in Belgium en N-France
La forêt de Flines, à la frontière franco-belge – Source : windstorm.111e-monsite.com
Conference Meteo Alarm Budapest 14 – 15 December 2009 55
Hail case of 25-26/05/2009 in Belgium en N-France
Some people collected the stones in the freezer, and I could recover Some people collected the stones in the freezer, and I could recover some of the biggest hail stones in the recent Belgian history…some of the biggest hail stones in the recent Belgian history…
Biggest stone recovered with a diameter of 9.2 cm
Conference Meteo Alarm Budapest 14 – 15 December 2009 56
Hail case of 25-26/05/2009 in Belgium en N-France
This case permited to make some cross sections of the biggest hail This case permited to make some cross sections of the biggest hail stones, with detailled photos as result with some stones, with detailled photos as result with some interesting interesting features …features …
Features like enclosed air bubbles, ring structure, embryo,…are very nice visible
Conference Meteo Alarm Budapest 14 – 15 December 2009 57
Hail case of 25-26/05/2009 in Belgium en N-France
Also, the lob structure and radial air channels are well distinguishable
Conference Meteo Alarm Budapest 14 – 15 December 2009 58
Hail case of 25-26/05/2009 in Belgium en N-France
Conference Meteo Alarm Budapest 14 – 15 December 2009 59
Hail case of 25-26/05/2009 in Belgium en N-France
What with the model indices?What with the model indices?
Conference Meteo Alarm Budapest 14 – 15 December 2009 60
Hail case of 25-26/05/2009 in Belgium en N-France
High STP/SCP valuesHigh STP/SCP values High EHI valuesHigh EHI values
Source: KMI/D. Dehenauw
Source: KMI/D. Dehenauw
Due to the model-convection, the model-fields Due to the model-convection, the model-fields were somewhat were somewhat disdisruptedrupted
Conference Meteo Alarm Budapest 14 – 15 December 2009 61
Hail case of 25-26/05/2009 in Belgium en N-France
Source: KMI/D. Dehenauw
Source: KMI/D. Dehenauw
Potential hailstone-diameter is estimated by the model, Potential hailstone-diameter is estimated by the model, based on the Fawbush-Miller algoritm (1). based on the Fawbush-Miller algoritm (1).
(1) Contribution to severe weather and multimodel ensemble forecasting in Belgium, PhD Thesis D. Dehenauw, 2006
18z18z 21z21z
Hail path
Conference Meteo Alarm Budapest 14 – 15 December 2009 62
Hail case of 25-26/05/2009 in Belgium en N-France
Conclusion: here the IConclusion: here the Ingredients-Based ngredients-Based MethodologMethodology y also also worked very wellworked very well
Conference Meteo Alarm Budapest 14 – 15 December 2009 63
Hail case of 25-26/05/2009 in Belgium en N-France
Conference Meteo Alarm Budapest 14 – 15 December 2009 64
Model convection is integrated in the map by blue shading
Regions with SWI > 0.8 are shown on a large scale
Jetstreaks are also integrated on the map
Tests of some indices on a global model (GFS) for larger regionsTests of some indices on a global model (GFS) for larger regionsRecent example of the low topped storm of November 23the, 2009 in Belgium/Netherlands
No model convection foreseen: smaller risk
Conference Meteo Alarm Budapest 14 – 15 December 2009 65
Tests of some indices on a global model (GFS) for larger regionsTests of some indices on a global model (GFS) for larger regionsRecent example of the low topped storm of November 23the, 2009 in Belgium/Netherlands
hail
15z
Conference Meteo Alarm Budapest 14 – 15 December 2009 66
Tests of some indices on a global model (GFS) for larger regionsTests of some indices on a global model (GFS) for larger regions
In Belgium, hail stones up to 5 cm in length fell near Bruges and had a very irregular shape
Recent example of the low topped storm of November 23the, 2009 in Belgium/Netherlands
Conference Meteo Alarm Budapest 14 – 15 December 2009 67
Tests of some indices on a global model (GFS) for larger regionsTests of some indices on a global model (GFS) for larger regionsRecent example of the low topped storm of November 23the, 2009 in Belgium/Netherlands
As with the hail storm of 25 May, I made some cross-section taken in transmitted light to retrieve internal details
I sent the full report of this hail case to the Meteo Alarm forum
Conference Meteo Alarm Budapest 14 – 15 December 2009 68
Tests of some indices on a global model (GFS) for larger regionsTests of some indices on a global model (GFS) for larger regionsRecent example of the low topped storm of November 23the, 2009 in Belgium/Netherlands
Wind damage
18z
Conference Meteo Alarm Budapest 14 – 15 December 2009 69
Tests of some indices on a global model (GFS) for larger regionsTests of some indices on a global model (GFS) for larger regionsRecent example of the low topped storm of November 23the, 2009 in Belgium/Netherlands
In the Netherlands, local important wind damage was registered
Conference Meteo Alarm Budapest 14 – 15 December 2009 70
Tests of some indices on a global model (GFS) for larger regionsTests of some indices on a global model (GFS) for larger regionsRecent example of the low topped storm of November 23the, 2009 in Belgium/Netherlands
model convection integrated in the SWI index
Conference Meteo Alarm Budapest 14 – 15 December 2009 71
General conclusions:General conclusions:
Despite the shortcomings of the IDespite the shortcomings of the Ingredients-ngredients-Based methodologyBased methodology using models using models (unrepresenative proxy soundings, (unrepresenative proxy soundings, shortcommings in the models, etc…), they shortcommings in the models, etc…), they can help the forecaster to show regions can help the forecaster to show regions where there could be a where there could be a threateningthreatening situation.situation.
Even in seeming harmless configurations Even in seeming harmless configurations (e.g tornado Hautmont), they can give (e.g tornado Hautmont), they can give important signals and then, the forecaster important signals and then, the forecaster can go in detail to find out if there realy is a can go in detail to find out if there realy is a threat.threat.
Conference Meteo Alarm Budapest 14 – 15 December 2009 72
Hail case of 25-26/05/2009 in Belgium en N-France
An attempt to forecast severe An attempt to forecast severe convection in a uniform and objective convection in a uniform and objective
way (the same methodology by all way (the same methodology by all the forecasters)the forecasters)
The ChecklistThe Checklist
Conference Meteo Alarm Budapest 14 – 15 December 2009 73
Online CHECKLIST for SEVERE CONVECTIONForecasting (severe) convective storms
383/8 18-00z
Conference Meteo Alarm Budapest 14 – 15 December 2009 75
Online CHECKLIST for SEVERE CONVECTION
Direct access to the model maps
Conference Meteo Alarm Budapest 14 – 15 December 2009 78
Online CHECKLIST for SEVERE CONVECTION
Color indicates if a treshold is attained
A risk is given for thunderstorm in general and also for severe storms
Some facultative info can be given – proposition of e.g warning color
The results ar for a cool air mass situation