What is a seasonal weather forecast?

If you want to understand how seasonal forecasts are made, think of how you yourself make forecasts without even thinking about it. When you see a black cloud coming your way fast, you will start looking for shelter. The reason is of course that your brain tells you that there’s an outsized chance of rain….

New paper on cold air outbreaks

Today my latest paper was accepted for publication in the Quarterly Journal of the Royal Meteorological Society. A preprint of the accepted version can be downloaded and viewed here. The title of the paper is Higher Ocean Wind Speeds During Marine Cold Air Outbreaks. Here’s the abstract: Marine cold air outbreaks (MCAOs) are large-scale events…

Installing ECMWF’s GRIB-API for Python on Mac OS

I just upgraded my MacPorts to Mac OS Sierra and expected some problems. First I followed the instructions on migrating. Then I uninstalled all ports and started installing the ones I needed as I went along. The ECMWF’s GRIB-API package is one of them. When installing through MacPorts, and if you need Python bindings, you must run: sudo…

Paper on polar lows submitted

Last week I submitted a new paper, where Tom Bracegirdle, Matthias Zahn and I used numerical models to study a “hurricane-like” polar low, to Journal of Geophysical Research–Atmospheres. The title of the paper is: Re-examining the roles of surface heat flux and latent heat release in a ‘hurricane-like’ polar low over the Barents Sea, and here’s the…

Polar low developing

I just wrote about a new polar low brewing and stewing off the coast of northern Norway on the Polar Lows blog. Here’s a nice satellite image:

Papers on weather persistence

I just submitted a paper that I wrote with co-authors Elizabeth Barnes and Stefan Sobolowski. It’s about trying to understand why the weather from one month to the next sometimes stays the same. For example, if January is really cold, it’s quite likely that February will be cold as well. Here’s the abstract for the…

Nice Christmas Polar Low

I just wrote about a polar low that dumped large amounts of snow on northern Norway during Christmas. Here’s a picture: And here’s the link to the full blog post: http://wp.me/p1iDnE-38

Paper accepted by Climate Dynamics

I just got a new paper accepted for publication in Climate Dynamics. The title is: Extreme small-scale wind episodes over the Barents Sea — when, where and why? and here’s the abstract: The Barents Sea is mostly ice-free during winter and therefore prone to severe weather associated with marine cold air outbreaks, such as polar…

New Scientist Special Report on Climate Change

I just scanned a special report on climate change from New Scientist 22 October 2011 edition. It’s a quick and good introduction to the science of climate change. The pdf file is found here: Click here to view the article online

Plot WRF domains in Google Earth

I’ve made a small python script to plot your WRF domains. It simply creates a KML file that can be opened in Google Earth, taking your geo_em* NetCDF files as input. Just go to the directory where the geo_em*.nc files are found, and run with: python plotdomains.py It will create a KML file called domains.kml….

Winter temperatures

This winter was unusually cold in many places in the northern hemisphere. But perhaps more surprisingly, in other places it was very warm. The map below shows temperature anomalies with respect to the mean over the last 30 winters (click for full size): Also shown are locations where the pressure was higher (H) and lower…

Nice forecast

This was the forecast for 19–20 November 2009. The numbers are in millimeters.