Example Vertical Profile Displays

Vertical Profile and ecCharts of MUCIN and MUCAPE

Fig8.1.8.1-1: Vertical profile at Mao (Mahon), Menorca, Spain  (arrowed) with MUCIN and MUCAPE, all from ecCharts:  T+108 VT 18UTC 12 Aug 2020, DT 00UTC 8 Aug 2020.  

Note: The diagram is output from Cy48r when the resolution of HRES (~9km) differed from the resolution of medium range ensemble (~18km) and so HRES and Ensemble Control Forecast differ.  With effect from Cy49r1, HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical and their results are a single trace on the vertical profile.

In Fig8.1.8.1-1:

In the Vertical Profile:

• The spread of ensemble temperatures is fairly large at this lead time and there are some differences in the detail near the inversion at around 950hPa.
• There are some very large differences among ensemble members regarding forecast dewpoints, especially between 700hPa and 400hPa and this is reflected also in the wide spread of the dewpoint depression trace (from 0ºC to ≥20ºC).  
• No information may be deduced regarding the temperature and dew points associated with each ensemble member.  In particular, at each level the values at the extremities of the dewpoint shading do not necessarily correspond to the extremities of the temperature shading (i.e. the highest temperatures are not associated with the higher dewpoints - indeed dewpoints on some ensemble members are higher than the lowest temperatures on some other ensemble members).  The important information is the spread, or the uncertainty, of the ensemble temperatures, dew points and dew point depressions.  

The spread of temperature and/or dew point temperatures could be due to differences among the ensemble models in:

• the evolution of the structure of the model airmass (e.g. differences in advection of model air masses). 
• the timing of features (e.g. movement of a front past a given location).
• general differences in the synoptic scale evolution (given that this is T+108).  This would have been a less likely reason at shorter leads.

On the MUCAPE diagram:

• 16 members need to overcome MUCIN of >200J/kg for MUCAPE to be released, and within this set the maximum MUCAPE is ~3000J/kg, the minimum is ~1800J/kg with the median value ~2700J/kg.  Thus there is potential for very active free convection (high MUCAPE) but significant energy input is necessary to release it.
• 30 members need to overcome MUCIN of between 50J/kg and 200J/kg for MUCAPE to be released, and within this set the maximum MUCAPE is ~3500J/kg, the minimum is ~1900J/kg with the median value ~2900J/kg.  Thus there is potential for active free convection (high MUCAPE) but only moderate energy input is necessary to release it.
• 4 members (2 have the same value) need to overcome MUCIN of <50J/kg for MUCAPE to be released, and within this set the maximum MUCAPE is ~2600J/kg, the minimum is ~1400J/kg (no mean value is given as there are ≤5 members).  Thus active free convection (moderately high MUCAPE) is available with quite low energy input necessary to release it.  

In general, there is no apparent relation between MUCIN and MUCAPE:

In this example:

• Where it is fairly easy to release free convection (i.e. a small amount of energy is needed - low MUCIN) it does not necessarily imply convection with large MUCAPE will follow.
• Where it is fairly difficult to release free convection (i.e. a large amount of energy is needed - high MUCIN) it does not necessarily imply convection with large MUCAPE will follow.

Other cases will of course have different characteristics.

Vertical Profile and ecChart of Probability of Convective Precipitation

Fig8.1.8.1-2: A forecast vertical profile for Premuda, Croatia T+90 VT 06UTC 18 Aug 2020, DT 00UTC 14 Aug 2020 . The corresponding ecChart shows the forecast probability for convective precipitation (same model runs).  

Note: The diagram is output from Cy48r when the resolution of HRES (~9km) differed from the resolution of medium range ensemble (~18km) and so HRES and Ensemble Control Forecast differ.  With effect from Cy49r1, HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical and their results are a single trace on the vertical profile.

In the case shown in Fig8.1.8.1-2 many ensemble members suggest MUCIN can be fairly easily overcome (MUCIN <50J/kg)  releasing quite vigorous convection (large MUCAPE values - Ensemble Control Forecast ~3500J/kg, ~3000J/kg).   The probability of precipitation chart shows that <35% of ensemble members are producing showers totalling >1mm in the period 00UTC to 06UTC.   Nevertheless the MUCIN/MUCAPE diagram suggests that quite active convection with heavier showers has been quite possible during the preceding 6hr period given sufficient energy input to overcome MUCIN - this might be dynamical or mechanical uplift. As this was night time it seems more likely that solar heating during the morning will overcome the MUCIN leading to active convective cells.

It is wise to consider both the probability of convective precipitation charts and the vertical profiles together rather than using either alone to assess the possibility of active convective cells.

Vertical Profile Sequence showing variation of MUCIN and MUCAPE through 24 hours

Fig8.1.8.1-3: Sequence of forecast vertical profiles for Brindisi, Italy illustrating the variation in MUCIN and consequent availability of MUCAPE through a full 24h diurnal cycle in which the structure of the atmosphere above the lowest layers remains largely unchanged. Here, for simplicity, MUCIN is defined as: low MUCIN<50J/kg, moderate 50J/kg<MUCIN<200J/kg, large MUCIN>200J/kg.  

Note: The diagram is output from Cy48r when the resolution of HRES (~9km) differed from the resolution of medium range ensemble (~18km) and so HRES and Ensemble Control Forecast differ.  With effect from Cy49r1, HRES and Ensemble Control Forecast are scientifically, structurally and computationally identical and their results are a single trace on the vertical profile.

In Fig8.1.8.1-3:

• At 00UTC 16 Aug: There is a low-level inversion and generally the lower layers have a low humidity.  The majority of ensemble members (46) suggest fairly active free convection (MUCAPE mostly >1000J/kg) could be released if sufficient energy were available.  HRES suggests less vigorous convection (MUCAPE~500J/kg) after MUCIN is overcome.   However, near the surface, some ensemble temperature and humidity values are high and a few ensemble members (3) suggest rather stronger free convection (MUCAPE>2000J/kg) could be released with only rather low energy input required to overcome MUCIN.  A small minority of ensemble members (2) indicate MUCIN will not be overcome and free convection will not be initiated.  At this time there is no solar energy to overcome MUCIN but the values shown give an indication of what would be required during the following 12hrs or so to release free convection.  Potentially mechanical or dynamical uplift will also play a part.
• At 06UTC 16 Aug: The low-level inversion has been somewhat eroded through early diurnal heating but some ensemble members show high low-level humidity.  Many ensemble members (28) suggest only rather low energy input is now required to overcome MUCIN and release moderately active free convection (MUCAPE<2000J/kg).  Other ensemble members (22) suggest more substantial energy input is required to overcome MUCIN and release moderately active free convection (MUCAPE <~1500J/kg).  At this time solar heating is becoming a major source of energy to overcome MUCIN, but potentially mechanical or dynamical uplift will also play a part.
• At 12UTC 16 Aug: The inversion has been broken and MUCIN is now small and free convection can be released by a further rise in surface temperature or by uplift of the moist zone near 900hPa.  However, uplift of drier low level layers shown by some ensemble members requires a more substantial input of energy sufficient to release free convection and MUCIN is consequently higher.  The resulting free convection is rather weak (MUCAPE<~1000J/kg), because of the lower near-surface dew points.
• At 18UTC 16 Aug: The low-level inversion is reforming with evening radiative cooling, or by shallow near-surface cold advection from the Adriatic on easterly winds, but the low-level humidity remains similar to earlier in the day.  Consequently MUCIN is increasing and more substantial energy input is required to release free convection.  The majority of ensemble members (47) suggest moderately active free convection (MUCAPE mostly <~1500J/kg) could be released if sufficient energy were available to overcome moderate MUCIN.  A small minority of ensemble members (3) indicate large MUCIN is required before releasing weaker free convection (MUCAPE <~500J/kg).  During the evening only mechanical or dynamical uplift is likely to supply the energy to overcome MUCIN.  
• At 00UTC 17 Aug:  The low-level inversion has reformed fully with high relative and absolute humidity in the near-surface layers.  MUCIN is rather larger than at 18UTC, on balance, and substantial energy input is required to release free convection.  Most ensemble members (32) suggest moderately active free convection (MUCAPE mostly <~1500J/kg) could be released if sufficient energy were available to overcome moderate MUCIN.  An increased number of ensemble members (14) indicate large MUCIN needs to be overcome before releasing weak free convection (MUCAPE <~300J/kg).  A small minority of ensemble members (4) indicate MUCIN will not be overcome and free convection will not be initiated.  Overnight only mechanical or dynamical uplift can supply the energy to overcome MUCIN.  

Although this case does not definitively highlight active convection, the hodographs indicate some vertical shear through the model atmosphere which would be conducive to organised deep moist convection if large MUCAPE were available and were released.

Forecast vertical profiles in the vicinity of a mobile cold front

Fig8.1.8.1-4: The ensemble forecast frontal zones from the cyclone database products (example) T+120hr VT:00UTC 22 Aug 2020, DT:00UTC 17 Aug 2020.  Inset shows magnified area around Denmark.  Animation of cyclone database products allows an assessment of the developing spread and changing intensity of frontal features. 

The ECMWF front spaghetti plot (Fig8.1.8.1-4) indicates that:

• there is a broad spread in ensemble cold front positions,
• but HRES (thick green line, strictly the front at 1km altitude) lies slightly towards the forward edge of the range of ensemble positions. 

When assessing the timing (and activity) during the passage of a front at a given location it is wise to examine:

• a fixed-time animation of synoptic charts from the cyclone database products (not shown) to assess the variation in synoptic pattern.
• an animation of the frontal zones from the cyclone database products (Fig8.1.8-9) to assess the evolution of the spread of forecast positions.
• vertical profiles on a pseudo cross-section spanning the range forecast frontal zones, to assess the higher probabilities of frontal structure (e.g. incursion of drier air, persistence of warm air, potential release of instability, frontal slope in the vertical).

Fig8.1.8.1-5: An example of forecast vertical profiles in the vicinity of a mobile cold front crossing Denmark, T+120hr VT:00UTC 22 Aug 2020, DT:00UTC 17 Aug 2020.  There are a range of forecast positions of the front among the ensemble solutions but HRES (thick solid) and Ensemble Control Forecast (thick dotted) both position the front approximately between Copenhagen and Odense.  The East/West section through this zone illustrates the differences in the structure of the model atmospheres, particularly in the spread of the ensemble temperatures and dewpoints. The pale blue colouring approximately encloses the range of ensemble positions for the front.  

Note: The diagram is output from Cy48r when the resolution of HRES (~9km) differed from the resolution of medium range ensemble (~18km) and so HRES and Ensemble Control Forecast differ.  With effect from Cy49r1, HRES and Ensemble Control Forecast are scientifically, structurally and computationally identical and their results are a single trace on the vertical profile.

In Fig8.1.8.1-5 the airmasses to the east and west of the frontal zone have some well-marked identifying features:

• to the east (55N 15E) there is a zone of warm air in the lowest layers (~24°C) and moisture content (~8g/kg) is uniform up to about 800hPa.  The spread of temperatures and dew points (darker shades of red and green respectively) is quite narrow with few outliers (lighter shading) suggesting confidence in the ensemble model structure of the pre-frontal airmass.
• to the west (56N 06E) the air is cooler (~18°C) and moisture content decreases rapidly with height.  The spread of temperatures and dew points (darker shades of red and green respectively) is quite narrow near the surface although there are outliers (lighter shading) suggesting some uncertainty in the structure of the ensemble model structure of the post-frontal airmass. In mid-levels confidence in dewpoint is low - this may signify uncertainty in where the (rearward sloping) cold frontal surface lies.

The remaining vertical profiles illustrate the transition between the air masses through the frontal zone with characteristics of both evident to a greater or less extent depending upon the positioning of the front by each ensemble member.

Some other interesting features can be identified; mostly the HRES and Ensemble Control Forecast runs (single thick lines) are representative of the ensemble, but in some respects they are not - e.g. the control has anomalously warm low level air well ahead of the front (55N 15E).