24 Sept KPNS forecast

posted Sep 24, 2012, 1:47 PM by Michael Baldwin   [ updated Sep 24, 2012, 1:49 PM ]
Current obs & SPC mesoanalysis showing large anti-cyclone centered over West Virginia, northerly/northeasterly flow from the East Coast into the Florida panhandle.  KPNS is located just to the north/east of a strong theta-e gradient as seen in the Purdue WRF frontal diagnostic and the SPC mesoanalysis.  Dewpoints dropped at KPNS during the early morning hours today as this frontal zone moved through the area.  This boundary between the cool/dry air to the east and the moist air to the west is predicted by the models to remain west of KPNS during the day on Tuesday.  Forecast soundings indicate stable and dry conditions for the day on Tuesday, so precipitation is not an issue for today's forecast. (not sure why the METARs are showing obs precip there today, this looks to be an error in the obs, don't get too excited about any precip that shows up in the scoring tomorrow, erroneous obs do get corrected in the scoring system)

Minimum temperatures should be a few degrees cooler than this morning's low of 68 given the drier air that is currently in place.  There may be some local effects due to the wind direction coming off of Escambia Bay that will keep the temperatures from dropping close to the current dewpoint values (upper 50's).  Although I won't be surprised to see upper 50's just north of KPNS, tricky aspect of the forecast is the wind direction overnight, if the winds keep purely out of the north, the temps could drop quite a few degrees cooler than expected.  Since both the NAM and GFS MOS values as well as the current NWS point forecast are going for a min of 62, I expect the consensus forecast from the contest will be right at that number. Low to mid 60's look reasonable to me. 

For their max temp, persistence should be an excellent forecast.  Basically zero change is predicted in the 850 mb temps between today and tomorrow, their max hourly temp so far today was 85, should be very similar tomorrow.  MOS guidance, NWS point forecast, and USL numbers are all in the 85-86 range, so something around 85-86 will likely be the consensus number and should be very close to the verifying obs.

Winds are also predicted to remain fairly light, all of the guidance values indicate something around 9kts, their max reported speed in the hourly METARs today was 8kts.

I think we are going to see a very "sharp" distribution of forecast values for KPNS today, centered right at the average guidance numbers: 
85/62/9/0.00 (max/min/wnd/ppt).  Don't read anything into your ranking after one forecast, since everyone is going to be clustered close together, tiny errors will be amplified into large scores as defined by the wxchallenge scoring system.  Today's a day to stay close to the consensus and look for opportunities to separate from the pack later (next week?) when/if the precip and wind starts to get more uncertain...
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