Sunday 2^nd March

Time for a brake (sorry)

Weather Outlook: There’s a change on the horizon from Friday, but until then conditions still good for polar lows.

Flight plan for tomorrow: Into a polar low to our NE, which may be a sensitive region, but the ETKF SAPs didn’t come through today.

Blog

No flight today, for technical reasons. The brake on the Falcon needed replacing, and this was done with great speed by aircraft technician Alex this morning. A short flight was needed to test the brakes this afternoon, and a second short flight carried cameraman Frode and dropsonde operator Christian so that they could get some shots from the air for the documentary.

Today we said goodbye to Astrid, leaving us for a week to see her young daughter, and Birgitte who is journeying on to Svalbard, where the daytime temperature is about -20degC! Tomorrow we also lose Swiss PhD student Thomas, leaving only seven scientists to conduct the next week of the campaign.

The afternoon flight planning discussions were rudely interrupted by the arrival of the 12Z HIRLAM forecast, which showed that the polar low that we thought was going to move slowly away from us, was actually going to develop and come straight towards us. A secondary low is forecast to form off it and hit Trondheim on Tuesday morning with 50kt winds! We have gone in search of bad weather but it seems that it is going to come to us. Frode rushed outside with his camera to film the clouds on the horizon as the sun went down – it’s the edge of the polar low that we can see. Now the 4km UM forecast has come in and it deepens the low that will hit us even further. Tonight will be a long night of flight planning, and then we’ll be up early tomorrow to finalise (e.g. change completely) the plans after looking at the 00Z forecasts. The documentary team are of course very interested in this, and are running round the ops room filming conversations. I’ve managed to keep out of the way, because I was trying to decode a radiosonde message from the KV Senja. It’s a coastguard ship that agreed to release radiosondes for us, but doesn’t want to give its position away, and I finally worked out that to achieve that they had decided to report the observation as if it were a land station, and therefore there was no latitude and longitude information in the message. It achieved its aim, but also made the observation useless, as we can’t use it in the model if we don’t know where it was taken!

Tomorrow we fly to map the structure of these polar lows, and see if putting observations in the forecast ultimately improves it. If we can get them onto the GTS that is…

Weather Round-up

Polar lows seem to be popping up everywhere. Another has appeared on the satellite image, to the north of Andøya, that was not forecasted. See the above for a description. The temperature difference between the sea surface and 500mb height is 51degC in the region where the low is forming.

SAP Evaluation

There’s no ETKF SAPs today, for reasons unknown. Given their recent form, and that the situation has changed little since yesterday it’s a pretty safe bet that the sensitive region is to our north!

The SV SAPs have the sensitive region inside the verification region for 12 and 24hrs optimization times, where there is weak westerly upper-level flow. For 36hrs optimization there is a second sensitive region in the lee of Greenland, where a low has developed, creating a tip jet. This low is forecast to weaken as it moves down towards the UK on Monday.