30 January 2014 In Blog style

MAJOR Old fashioned Rocky Mountain Snow Storm 30-31 Jan 2014

A typical Rocky Mountian snowstorm was triggered by the subtropical jet stream from Hawaii to Oregon and California and down into Colorado which was well predicted by numerical models and NOAA and local forecasters.  This jet was clearly seen in the water vapor imagery shown in Figure 2 from the NOAA Eastern Pacific satellite imagery at 1530 UTC on Jan 30, 2014.  It produced over 15 inches of new snow at my home in Summit County, CO at 9684 ft msl (2952 m msl) between 0200 and 0700 MST. Figure 1 shows a typical photo on our deck at 0700.  The total by 1600 MST today reached 21 inches with S to S+ continuing and over 0.80 inches of snow water equivalent.  Snow depths at standard snow poles are approaching 48 inches (122 cm) now.  Day 2 of storm produced another 14.5 inches and 0.99 inches of snow water equivalent for a total of 27.5 and 1.64 inches of water.  The snow continues to fall lightly in the strong SW flow into the 3rd day 1 Feb 2014. 

Figure 1.  Photo of deep snow on our deck.

Figure 2. Water Vapor satellite imagery over eastern Pacific Jan 30, 2014 1200 UTC from NOAA.

imagery showing the subtropical jetstream extending from Hawaii NE to California bringing beneficial snows and rains to California and the Sierra, and heavy snows to Colorado.

The US Navy NOGAPS Model among others predicted the cutoff of the Pacific Coast ridge which had kept California in drought and warm temperatures all winter.  Figure 3 shows this initial model analysis and Figure 4 shows the 72 hour prediction of the major jet impacting the west coast and into Colorado at the 300 mb jet stream level (9300 m msl).  Note the strong “polar vortex” again over E North America that brought bone chilling cold to the East.


Figure 3.  NOGAPS US Navy model analysis of the 300 mb level jet stream pattern on 27 jan 2014 at 1200 UTC.  This is the initial stage of the Pacific Ridge breaking down and allowing Pacific moisture flux into California and across the Rockies.




Figure 4.  Same as 3 with 72 hour prediction for 30 Jan 2014.

The NOAA National Centers for Environmental Prediction NCEP’s Hydrological Prediction Center HPC made a 48 hour total precipitation forecast for 30 Jan -1 Feb 2014 3 days ahead that predicted a major storm over Colorado’s Rockies.  Figure 5 shows this forecast for a maximum of 1.82 inches, and 1.36 over the central Sierra Nevada in California.


Figure 5.  Quantitative Precipitation Forecast QPF by WPC for 30 Jan-1 Feb 2014.

The moisture flux over the mountain barriers is the key to significant precipitation.  Moisture flow at the 700 mb level (3000 m msl) provides an excellent indicator of precipitation potential. The models also predicted this quite well as shown in figures 6-7 for the NOGAPS model.


Figure 6.  NOGAPS 700 mb flow with vertical motion and relative humidity fields in the 36 hour forecast for 0000 UTC Jan 31, 2014.  This forecast verified well on Friday 30 Jan 2014 shown in fig. 7.




Fig 7. NOGAPS 700 mb flow in the 12 hour forecast for 31 Jan 2014 at 0000 UTC.  this shows the strong continuing moisture flux across Colorado.

 RADAR for the US and Colorado clearly showed the beneficial precipitation from this storm from California to Colorado.  The NCAR RAP Real-Time Weather web site provides an excellent summary of RADARS across the country.  At 2300 UTC on Jan 30, 2014 we see  the intense snowfall over Colorado on the country-wide site (Fig 8) and the Colorado regional reflectivity data (Fig 9). 



Figure 8. Radar across the US at 2300 UTC Jan 30, 2014.



Figure 9. Radar from regional radars in Colorado at 2300 UTC Jan 30, 2014.




22 January 2014 In Blog style

Vigorous Winter - January 2014

Much of the world had extreme winter conditions in late December and January.  The Central and Eastern US had many record breaking low temperatures and stormy winter weather while the West had record warm and drought conditions.  The Polar Jet stream was very strong with a near zonal flow from North Africa thru Asia and across the Pacific to north of Hawaii where it took a sharp turn to the north into Alaska and then south around a quaisi - stationary polar vortex over the Hudson Bay region.  This Low pulled down very cold Arctic air into Eastern North America and triggered many strong coastal storms that moved into the North Atlantic where they maintained a strong Icelandic Low.  This produced a strong southerly flow that warmed Western Europe and the UK, while generating an extreme snowstorm over Norway with 1-2 meter deep snowfall.  Figure 1 shows the 300 mb analysis by the US Navy NOGAPS global model on January 22, 2014 from the Navy Research Laboratory's operational global modleing web page.

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Figure 1.  NOGAPS 300 mb Northern Hemisphere analysis on Jan 21, 2014 at 1200 UTC.

Note the zonal jet stream flow across the Pacific to 180 W then the sharp northern flow to Alaska and polar vortex flow over eastern North America.  A vigorous storm exits New England, where 15-18 inches of snow fell and temperatures dropped to 0 F. 

This deep cold low over Eastern Canada continued to maintain the extreme cold "Polar Vortex" pattern shown on the Environment Canada analysis of 26 January 2014 shown in figures 2 and 3 for the northern hemisphere surface and 250 mb analyses at 1200 UTC.  Note the deep low ( 977 mb ) over Laborador and the upper level low centered on Hudson Bay with the western North American Ridge on the west coast extending into Alaska. This ridge of warm air flowing northward into Alaska and the Yukon Territory provided strong moisture flux from the Pacific which recurved south into the Polar Vortex and produced heavy snows across central N America to New England.  In early January this same flux added to the snow pack in the Colorado Rockies.


Figure 2.  Northern Hemisphere Polar regions surface analysis on 26 Jan 2014 at 1200 UTC.




Figure 3.  Same as Fig. 2 for the 250 mb level model analysis showing the "polar Vortex" over Hudson Bay.

The sea surface temperatures (SST) have remained 2-3 C above normal in the east north Pacific as shown in figure 2.  This warm water provides significant energy for the series of very intense Aleutian Lows which helped maintain the ridge along western North America between them and the polar vortex over Hudson Bay region of eastern Canada.  This quasi-stationary pattern reinforced the extremely cold winter in the East.  



Figure 2.  Sea Surface Temperature (SST) anomaly for Jan 12 to 18, 2014 from NOAA's Earth Systems Research Laboratory's PSD Map Room .  Note the very warm NE Pacific anomaly south of Alaska, and moderate warm anomaly on the East Coast of North America.  There is a weak la Ninja.  This configuration of SST is likely responsible in part for the quaisi-stationary jet stream pattern that has kept Eastern North America very cold and western Europe relatively warm.  The Antarctic has also had a very strong summer jet stream pattern this Janurary which resulted in unusually cool temperatures in New Zealand and Australia, and strong storms off South America.