Last week was eventful in the weather and news world. Radical Islamists ravage Paris and kill 17 people including 12 at Charlie Hebdo and Hyper Cacher. Boko Haram strikes again in Nigeria and killed as many as 2,000 people in Baga and surrounding areas. As terrorism ravaged the world, last week was quite cold as the surface high came down south. The cold air was generally east of the Continental Divide. It was very cold especially near the America and Canada border. The Western US enjoyed summer in January. Here is a Northern Hemisphere temperature anomaly map.
Why was it cold east and warm west of the Rocky Mountains? There are many reasons for that. Here is a upper level map.
There is strong upper level ridging over Alaska and Eastern Russia, which indicates a negative East Pacific Oscillation (EPO) and West Pacific Oscillation (WPO). The strong troughing over Hudson Bay and Greenland is positive North Atlantic Oscillation (NAO) or Arctic Oscillation (AO). There is also strong upper level ridging over Washington and British Columbia, which is a positive Pacific/North America (PNA). A negative NAO, AO, EPO, and WPO allows cold air to go down south. However, only EPO and WPO were negative, while NAO and AO were positive. Despite being chilly in Texas, it could of been much colder as the sea level pressure was high, which is due to negative NAO and AO. The warm January the Western US experienced is from positive PNA. Had PNA been negative, the Western US would of been cooler.
So, why the positive NAO and AO? The surface pressure over Greenland was lower than normal, while the surface high off the coast of Portugal was higher. That setup allows a positive NAO. Had the surface pressure over Greenland and near Portugal had been weaker, NAO and AO would of been negative. That would of allowed more cold air to come down south along with EPO and WPO. Here is a sea level pressure anomaly map.
The pressure was higher than normal higher throughout North America and North Atlantic. Let’s head into this week’s forecast.
Here is a 5 day upper level and surface pressure forecast map. It is for the Northern Hemisphere as it is Winter. Again, special thanks to Levi Cowan of Tropical Tidbits.
All the forecast models from GFS, EURO, Canadian, and Japanese show upper level troughing over Alaska, Eastern Russia, Hudson Bay, and Greenland. This indicates a positive EPO, WPO, NAO, and AO. When that happens, the cold air stays in the Arctic as the jet stream is up north instead of being further south than usual when there is upper level ridging. Here is a temperature forecast model in 5 days.
The GFS shows most of the Lower 48 warmer, while Canadian has the southern half of the US cold again. The GFS and Canadian are split on temperature. In my opinion, with upper level troughing over the polar regions, it should be warmer. All the cold air bottled up in the Arctic region as the jet stream is up north, not far south. As a result, the warm air comes in from zonal wind flow from the west. Before the warmth, there is another cold front, but the cold air should not last as long like last week.
So, how will this week will be like if we use analog forecasts? Here is a 8 to 14 day analog forecast.
Some of these dates stand out. Here are the dates that stand out.
2/4/2004-Snow falls in Central Texas on February 14, 2004. Austin: 1.60″; San Antonio: 0.70″.
2/3/2003-Snow falls in Central Texas on February 8, 2003. Austin: 0.40″; San Antonio: 0.10″.
1/20/1980-Heavy rain falls in Southeast Texas between January 20-22, 1980. It leads to flooding in the Houston area. Three day totals are Bush Intercontinental: 4.61; Hobby: 6.00″; Galveston: 2.64″; College Station: 2.62″.
2/7/1997-Heavy rain falls in Houston area on 2/12/1997. Bush Intercontinental: 2.20″; Hobby: 3.54″; Galveston: 1.74″. Third wettest day at Bush, while wettest day on record for Hobby.
2/6/2005-February 2005 is one of the wettest February on record for Southeast Texas.
1/23/1968-Highs in the 70s from January 25 to February 1, 1968 are recorded at Houston WB.
1/14/2001 & 1/15/2008-Period of wet weather in January 2001 for Southeast Texas.
Looking at the analog forecasts, this suggest we could be in for a wet pattern and warmth. Freezes did occur, but they were not prolonged. I think warmth will be king for this week.