3 hr accumulated precipitation valid at 2100 UTC

3 hr accumulated precipitation valid at 0000 UTC

Radar image valid 0000 UTC

IR Satellite image valid 0000 UTC

Radar and satellite Imagery are indicating that an MCS is developing over eastern Montana and that a few cells are also developing over central South Dakota

 

3 hr NAM accumulated precipitation valid at:

0300 UTCZ

0900 UTC

1200 UTC

The NAM forecasts very little precipitation with the blob moving eastward from MT and instead forecasts its development over eastern SD into MN.  First, concentrate on the MCS developing in MT and try to forecast its movement from the following model output. 

0000 UTC forecast sounding at the location of the red dot along the ND/SD border on the earlier maps.  A few important details about the sounding:  CAPE=1338 J/kg, PW=1.14”, LCL=690mb, Mean RH=49%, Mean LRH=37%

0300 UTC forecast sounding at the location of the red dot along the ND/SD border on the earlier maps.  A few important details about the sounding:  CAPE=1320 J/kg, PW=.95”, LCL=727mb, Mean RH=31%, Mean LRH=39%

The red dot is the location of the soundings below

NAM CAPE and CIN  valid 0300 UTC

NAM 850  wind, Øe and Øe  advection valid 0300 UTC

Using the sounding above and forecast fields, decide on which vector method to use from the maps below,  the original or revised vector methods.  Then,  use the following Corfidi vector wind forecasts to forecast the movement of an MCS that is moving from Montana into the Dakotas.  The new vector method winds are on the left hand side and the original vector method winds are on the right. 

NAM 0300 UTC revised  method winds

NAM 0300 UTC original CMF method winds

NAM 0600 UTC revised  method winds

NAM 0600 UTC CMF original method winds

Now that you picked which method to use.  Forecast the direction and speed of the MCS as it moves across the Dakotas. 

Which of the following do you think will be closest to the actual speed and movement of the MCS  .

A)  270o (east) at 15 knots

B)  270o (east) at 30 knots

C) 270o (east) at 40 knots

0200UTC radar

1000 UTC radar

The MCS moved at about 45 Knots to the east.

The more of these questions that you can answer with a yes,  the better the probability of a forward propagating MCS and the better the revised vector method will work. 

Adapted from Moore’s COMET presentation

Exercise 1 continued

1.)  Are moderate to strong mean winds present in the cloud bearing layer.

 

2.) Is there a dry layer present in the mid-levels or in the subcloud layer?

 

3.)  is there an area of favorable CAPE coincident or downstream of the initial convection.

 

4.)  Is a 850 hPa theta-e ridge downstream or coincident with the convection.

 

5.) is the low-level jet and axis of strongest low level moisture flux coincident or downstream of the convection.

 

6.) Is the MCS moving with a mid-level trough.

 

7.) Is there and area of low-level convergence located along and downstream of the convection. 

 

Below is a list of questions you should ask when trying to decide whether of forward propagating MCS is more likely than of backward propagating one.