Tuesday 4^th March

A Bad Day To Visit Norden Trondelag!

Weather Outlook: Quietening down here the next few days

Flight plan for tomorrow: No flight

Blog

Like I said in the title, if you chose to visit Norden Trondelag or nearby Trondheim today, you made a bad choice! Making landfall is a polar low with strong winds and high waves. The models show 40kt winds at the surface for 6am this morning, but the satellite wind data (QuikScat) shows 50kt winds! In short, the models seem to be doing a good job predicting where the storm will be (so far), but are underestimating the windspeed and possibly also the precipitation that are going to come from this storm, and it’s these things that will cause damage to the area of Trondheim. We are getting ready to fly through the storm this morning, with Øyvind (Met Norway) as passenger. There is normally no space for passengers on the Falcon, but due to hard disk problems with one of the LIDARs it couldn’t be used today and so there was room for one scientist. The flight went well, launching and transmitting 20 sondes to the GTS, and flying through the middle of the polar low before it hit Norden Trondelag, halfway up the Norwegian coast.

Polar low centre

Andøya, where we are located

The polar low as seen on infra-red satellite images at 8am this morning, with associated rain bands.

Today’s activity at HQ was centred around the polar low. The latest satellite images and radar were carefully monitored, as were the soundings when they became available. It became clear during the day that the polar low was moving slower than the models had predicted and deepening more as it moved over the warm ocean currents near the coast. It was moving more to the left than forecast, looking like it might make landfall later and slightly further up the coast than had been forecast.

The down day tomorrow gives everyone a break and a chance to rest after all the activity of the previous week. In celebration of the successful flights, and because there was no need to get up early the next day, a small party was planned for the evening, with desserts being prepared by Andreas and Vanda. Erik arrived just in time to join the party, bringing photos of the polar low that he had flown over on his flight from Longyearbyen (Spitsbergen) to mainland Norway. Andreas and Vanda with some help (or hindrance) from the other scientists prepared crepes with fruit inside and chocolate sauce on top, which were delicious even if our resident cameraman tried to put us off eating by filming.

Weather Round-up

Polar low tomorrow at midday is at 73N, 8W, just north of Jan Mayen. This small feature merges with the large synoptic-scale cyclone that hits Trondheim with considerable force on Thursday. The event does seem to be well predicted, so even though it may be a sensitive region there seems to be little point flying into it and dropping sondes to try and improve the forecast. The lack of weather discussion here is mainly because we spent so long discussing the polar low that I didn’t get time to write much!

SAP Evaluation

The ETKF SAPs for all optimisation times highlight the northern edge of the low pressure system that is developing and moving towards Norway, making landfall in the verification region around 12Z on Thursday (e.g. potentially 24hrs after targeting). They also highlight where a small polar low is forming, just north of Jan Mayen and moving towards then merging with a larger cyclone before it hits Norway.

The SV SAPs also highlight this low pressure system as sensitive, and have some overlap with the SVs. The SVs for 12hrs optimisation indicate that the southern and eastern parts of the low pressure system are most sensitive. For 24hrs optimisation the eastern and northern parts of the low pressure system are more important. This region is also highlighted by the 36hr SV SAPs, as well as a region over Greenland, where the upper-level flow is coming from.