Monday 3rd March


Polar Lows!


Weather Outlook:  Polar low hitting Trondheim with 60kt winds tomorrow at around midday…

Flight plan for tomorrow: …which we are going to fly through as early as possible




There are towering cumulonimbus (thunder-) clouds on the horizon, out to sea.  They’re the edge of a polar low which is hitting the Lofoten islands today, and that we are flying through.  Today and tomorrow look to be the most exciting of the campaign – we came here to hunt polar lows and two are forming on our doorstep!  Naturally the documentary crew are also excited about this, and decided to film us at breakfast this morning; the first time they’ve filmed us in a non-work setting.  It’s quite disconcerting being filmed when you’re eating your cornflakes at 8am. 


Things quietened down a little in the afternoon, as Jon Egill, Mel and Vanda went to the airport to meet the Falcon on its return from its first flight and make last minute adjustments to the plan for the second flight while the aircraft was being refueled.  Christian did a fantastic job of dropping 21 sondes, and getting most of them transmitted during the flight, and the rest upon landing.  Thanks to Keir Bovis at the Met Office we know that the sondes made it to the Met Office observations database, and tomorrow we will see if they made it into the forecast or not.  I took advantage of the quiet to go for a walk along the coastline, and take photos of Andenes and the mountains behind the rocket range (see the updated photo album).


As I write this it is snowing and the wind has become quite gusty.  Flight planning is going on late and will resume tomorrow morning when the latest forecasts have come in.


Weather Round-up


The 00Z forecasts show a polar low spinning up and moving towards Trondheim, hitting it with 60kt winds and 10m waves tomorrow around midday.  This was also seen in the 12Z forecasts yesterday, so the forecasts seem to be converging on the same thing now.  The coarser resolution forecasts don’t have this very well – it’s a small feature.  The UM 4km box doesn’t go as far south as Trondheim, but the low just off the coast of Lofoten is not forecast to make landfall until 00Z on Tuesday.  The 06Z HIRLAM forecast has the low over Lofoten to be much weaker, making landfall this morning.  From looking at the satellite and radar images (the storm is now in range of the weather radar here) this is seen to be correct.  The HIRLAM forecast has the low hitting Trondheim some 3-6hrs ahead of the HIRLAM model, and also has the feature better resolved and stronger winds. 


There is a low pressure system forecast to move across the top of Iceland, deepen to have strong winds and hit southern Norway on Wednesday evening.  Poor Trondheim is getting hit again, with 60kt winds! 


Thursday to Monday the flow is off the mountains of Norway, giving good conditions for mountain waves.  There will also be strong winds exiting the fjords.


SAP Evaluation


The SV SAPs for 12hr optimization time have the region of maximum sensitivity fragmented.  There is a large area in the lee of Greenland, highlighting a low pressure system that is forecast to move towards Norway and deepen over the next couple of days, not 12hrs.  There are small regions of sensitivity within the verification region, one of which highlights the SW quadrant of the polar low that is forecast to hit Trondheim tomorrow with strong winds in that sector.  The SV SAP for 24 and 36hr optimization has the region of maximum sensitivity between Greenland and Iceland, ahead of the rapidly developing low pressure system in the lee of Greenland, and in an area that we are watching carefully as the satellite images suggest some development there.


The ETKF SAP for 12hr optimization also highlights the low pressure system that will hit Trondheim, although the low is not resolved in the forecast.  The region of maximum sensitivity extends north to Svalbard, highlighting the area of low pressure of the northern coast of Norway.  The ETKF SAP for 24hr optimization has a long thin region of maximum sensitivity at 70degN extending from the east coast of Greenland to 5degE.  For 36hrs optimization the sensitive region is in the lee of Greenland, where the low is – this low has some ensemble spread associated with it, which may explain why it has been picked out by the ETKF.