Aug 9, 2012 CTC & Radar Comparison

Given active weather pattern (deepening upper level trough over Great Lakes) with showers and storms over Wisconsin, it wasn't hard to find quick growing cells with at least moderate Cloud Top Cooling (CTC) rates.

There were some breaks in the cloud field over northwestern Wisconsin.  Perhaps this helped oen cell in a line to pulse up.  We were able to spot CTC rates in the moderate range with a value of 17 to 18 over northwestern Washburn County.  Further north in St. Louis County of northeastern Minnesota we observed a CTC value of 12 to 13. See Figure 1 below.

Figure 1. Maximum CTC rates of 17 to 18 over Washburn County.

 We then compared the cells with decent CTC rates with what the WSR-88D Radars depicted.  SEe Figure 2 below for the radar image which corresponds to Figure 1.

Figure 2. Radar image at 1643Z August 9, 2012.

The decent CTC rates would imply an increase in cell intensity observed on radar.  This intensity increase is noted in Figure 3 below, especially in the St. Louis cell which had a 60 dBZ signature.  Of course, these storms were not severe, but it was nice to see that the CTC rate idea enabled us to anticipate an increase in cell intensity.

Figure 3. Radar image at 1706z August 9, 2012.

Rusty Kapela - MKX
Ed Townsend - MKX
Justin Sieglaff - CIMSS

August 9, 2012 GOES-R FLS

This was my first exposure (shift) with GOES-R material (luck of the draw?).  Appreciated the lesson and learned a lot. I was impressed with the probability FLS image and comparing it to the older satellite images of low clouds/stratus.  I can see the utility with generating the TAFS...the FLS product will give me more confidence to go or not go with fog/stratus IFR conds.  The limitations at twilight were explained....makes sense.  Always great to have more tools at our disposal!

Some examples of the FLS probability product are shown in central Indiana. In Fig. 1, you can see a known characteristic with the cloud depth product, wherein the cloud phase product shows ice-based clouds "blacked out".  This is a result of the cloud depth product being limited to water-based clouds.  Also, note in Fig. 1 a swath of greater than 50% prob is located in east central IN. The nearest stations are showing CIGs of 110 and 95 hft and are outside this yellow swath.

Fig. 1. 1302Z: Cloud depth, IFR FLS Product, VIS Sat, GOES Cloud type(from top-left going clockwise).

In Fig. 2, the FLS product is now showing high probability of fog or low-level stratus.  However, the obs in the center of this high probability swath is reporting clear skies at 10 SM visibility.  Vis satellite was inspected and it reveals broken-overcast skies in this swath of high probabilities.  This was an interested feature given the initial discrepancies between the observations and the FLS product.  However, it was noted that the report of the obs was 1353 Z.  Wherein the satellite products have a time stamp of 1332. Thus, this is more so an artifact of this case (postmortem), where the observations and satellite products are not synchronized.  In a real-time situation, this is not anticipated to be an issue.

Fig. 2. 1332Z: Cloud depth, IFR FLS Product, VIS Sat, GOES Cloud type(from top-left going clockwise).

 In Fig. 3, the FLS product time stamp is 1402, which is now better aligned with this aforementioned METAR report at 13:53.

Fig. 3. 1402Z: Cloud depth, IFR FLS Product, VIS Sat, GOES Cloud type(from top-left going clockwise).

Further to the west, over the MKX WFO the GOES-R FLS IFR product performed well depicting the gradient in ceilings.  With low probabilities along a Madison to Milwaukee line; but increasing probabilities towards Wisconsin Dells  to West Bend.  Fig. 4 illustrates that the higher IFR probabilities to the north indeed matchup with lower ceilings, around 500 feet.  The ceilings over Milwaukee and Madison were 2700-4300 feet.

Fig. 4 1332 UTC Cloud depth, IFR FLS Product, GOES VIS, Heritage Fog GOES BTD(from top-left going clockwise).

To the northwest, the GOES-R FLS IFR probabilities captured a small, yet operationally significant area of low ceilings near and east of Fargo, ND  (Fig. 5).  The surface observations agree with the higher probabilities with 500-900 foot ceilings.

Fig. 5 1132 UTC Cloud depth, IFR FLS Product, GOES VIS, Heritage Fog GOES BTD (from top-left going clockwise).

It should be noted AWIPS @ MKX has been rolled back to an older version in preparation for upgrades to AWIPS-II.  As such, the products and enhancements are not current.

Ed Townsend - MKX
Rusty Kapela - MKX
Justin Sieglaff - CIMSS