The storm system scooting through on Tuesday will likely be low amplitude, fast moving, and ride the Canadian border in zonal flow. However, model guidance continues to advertise marginal criteria for snow mixing in down into northwest Massachusetts. No accumulation is expected, but up to an inch in the high elevations further north.
Believe it or not we have another potential storm to discuss for late next week. The GFS and ECM are on board with low pressure ejecting out of Texas on Thursday and moving to the Carolina coast by late Friday. This storm coincides with a negative AO and NAO and rising PNA in the west. The GFS ensembles bring the low up toward the Great Lakes. The ECM brings low pressure near the Cape Saturday morning. Both senarios would still likely drop accumulating snows on the front end of the storm. The main difference between the two is the magnitude of ridging out west and how much the -EPO breaks down. The operational GFS is a little different altogether as it develops a lead short wave that affects New England Thursday night. This is more unlikely though and the second wave should become predominant in the next few days of runs.
Anyway, some interesting bits to keep an eye on this week. Even first flakes would be fairly early, let alone accumulating snows. It's six days away and it's October, so Murphy's Law should be kept in mind.
Saturday, October 10, 2009
Friday, October 9, 2009
Spring training for models
The current situation across the globe is not model friendly. Certain developments in the tropics such as a brief stint for the MJO wave, and uncertainty with a propogating westerly wind burst are playing havoc with the long term model projections.
Short term forecasts are suffering a bit as well. The ECM and GFS recently shifted toward a more zonal regime for early next week, compared to the blast of cold air that had been suggested previously. The consequence of this flow is that the energy responsible for storm potential Monday - Tuesday next week will be unable to dig south much, and rather will ride across New England, keeping cold air locked further north.
Overall, the potential still exists for some first flakes in portions of central New Hampshire and the mountains into southern Vermont. Otherwise, a period of light rain showers can be expected for interior southern New England.
Short term forecasts are suffering a bit as well. The ECM and GFS recently shifted toward a more zonal regime for early next week, compared to the blast of cold air that had been suggested previously. The consequence of this flow is that the energy responsible for storm potential Monday - Tuesday next week will be unable to dig south much, and rather will ride across New England, keeping cold air locked further north.
Overall, the potential still exists for some first flakes in portions of central New Hampshire and the mountains into southern Vermont. Otherwise, a period of light rain showers can be expected for interior southern New England.
Wednesday, October 7, 2009
Snow potential early next week
Model guidance continues to support the idea of low pressure deepening near Cape Cod around Columbus Day. The GFS has been particularly robust with crashing heights over New England and the establishment of marginal criteria for snow in central and northern New England and potential for significant accumulations. Obviously, the higher elevations have the best chances.
The ECM has also been on this bandwagon. The 00z run takes the low a little further south, and consequently also brings colder air further south. Track nuances are far from being locked down. This potential storm is still around day 6 so there is much opportunity for changes. However, model agreement for a storm in this period is good. Given a supply of cold air, the chances for at least some first flakes as far south as the higher terrain of Massachusetts is looking good as well.
The ECM has also been on this bandwagon. The 00z run takes the low a little further south, and consequently also brings colder air further south. Track nuances are far from being locked down. This potential storm is still around day 6 so there is much opportunity for changes. However, model agreement for a storm in this period is good. Given a supply of cold air, the chances for at least some first flakes as far south as the higher terrain of Massachusetts is looking good as well.
Sunday, October 4, 2009
Winter approaches
Yes it's only the start of October, but I can tell you that seeing snow showers over the mountains in northern New Hampshire certainly gives a feeling of anticipation.
The month has gotten off to very chilly start across the entire nation. From the Rockie Mountains to New England, temperature anomalies are in the -5 to -10F range and lower. In fact southern Texas is the only area that has positive anomalies for the last three days.
We should see a respite from the cold this week, however the long range model guidance has been adament in delivering an early season blast of frigid air days 8-10. The two primary models, the GFS and ECM, develop above normal heights over the arctic while at the same time dropping a major trough into the eastern half of the conus. Verbatim, records could be threatened.
In addition, the model continue to show a storm system passing near New England around Columbus Day. With such a cold air mass over the eastern US and a still very warm Gulf Stream, a strong baroclinic zone develops along the coast. This could promote a significant deep storm tracking up the eastern seaboard. This is all speculation based on long range models that are sure to shift around over the next week, however given these circumstances, portions of interior New England could see an early appearance of some snow.
The month has gotten off to very chilly start across the entire nation. From the Rockie Mountains to New England, temperature anomalies are in the -5 to -10F range and lower. In fact southern Texas is the only area that has positive anomalies for the last three days.
We should see a respite from the cold this week, however the long range model guidance has been adament in delivering an early season blast of frigid air days 8-10. The two primary models, the GFS and ECM, develop above normal heights over the arctic while at the same time dropping a major trough into the eastern half of the conus. Verbatim, records could be threatened.
In addition, the model continue to show a storm system passing near New England around Columbus Day. With such a cold air mass over the eastern US and a still very warm Gulf Stream, a strong baroclinic zone develops along the coast. This could promote a significant deep storm tracking up the eastern seaboard. This is all speculation based on long range models that are sure to shift around over the next week, however given these circumstances, portions of interior New England could see an early appearance of some snow.
Saturday, September 19, 2009
Preliminary Winter Outlook posted
The KeeneWeather.com preliminary 2009-10 winter outlook has been posted on the main page.
Click here for full details!
Click here for full details!
Tuesday, September 15, 2009
PRELIMINARY 2009-10 WINTER OUTLOOK
Summer Analogs:
The summer of 2009 had a number of distinct features including height anomalies associated with a predominantly negative NAO and AO while an El Nino built in the equatorial Pacific. The top analogs for the observed H5 pattern were 1950, 1951, 1958, 1960, 1965, 1977, 1982, 1985, 1998, and 2004. Filtering for the prefered ENSO conditions (details below), the list is condensed to 1951, 1958, 1965, 1977, 1982, and 2004.
Pacific:
Between April and June, SSTs in the equatorial Pacific warmed rapidly triggering a lot of "strong" El Nino talk. However, in late June, trade winds strengthened over the eastern Pacific, subduing the high SST anomalies. There have been multiple west wind pushes west of the dateline, but propogation into the western hemisphere has been minimal.
So what we've seen is a stall in the warming of the EPAC while central Pacific SSTs have been on the increase. At the start of September, the highest totals were located between 160E and 180. SST anomalies have the greatest effect in the western Pacific where totals are the highest and the exponential relationship between saturation vapor pressure and temperature dictates that evaporation rates are increased significantly with small deviations in SST. The west-based versus east-based argument matters with respect to where forcing is positioned, so even though SST anomalies may be slightly higher at times in the east Pacific, their effects are not as great and the anomalies near the dateline will have much more significance. Overall, I expect this El Nino episode to at least remain within the moderate threshold.
The convergence of the trade wind anomalies with the westerly wind bursts has provided focus for tropical convection, and we have seen this summer a number of OLR minimas just west of the dateline. Also, it should be noted that the summer analog composites display this well too.
In the north Pacific, there has been notable cooling near and south of the Aleutians. The -PDO has weakened to it's highest state since September 2007. However, at the same time, SST anomalies have cooled in the Gulf of Alaska. This has influence over the location of a trough over the north Pacific. It is clear that the north Pacific pattern will be a crucial battle ground this winter.
Atlantic:
SST anomalies in the north Atlantic have been tilted squarely toward a winter +NAO configuration. Using a regression with the two regions of interest yields a DJF NAO of +.85. However, the equatorial Atlantic is looking more favorable. There has been a general cooling of waters between Africa and South America. This should have overall weakening effect of the Atlantic hadley.
In addition, with primary tropical forcing occurring near the dateline, and some weaker forcing through the eastern Pacific, this forces an equatorial cell with sinking air over South America which again, weakens the Atlantic Hadley, and assists in the development of a -NAO.
Stratosphere:
Stratospheric easterly wind anomalies continue to make their descent, and the QBO took a steep dive this summer. Easterlies will continue to descend this winter, and the QBO will likely bottom out sometime in the spring. The descending, negative phase along with a warm ENSO period is highly supportive of a weakened polar vortex.
Preliminary Outlook:
There are definitely inconsistencies between each analog. I do not intend on using them directly, rather just as guidance for the outlook. Overall, there is a decent consensus for a dominant +NAO in December, a transition phase in January, and a dominant -NAO from late January through February. January and February could certainly feature a couple major winter storms in the eastern US. One significant x-factor is the North Pacific pattern. I think we will see the PDO become more neutral toward the winter, but another question is what happens with SSTs in the Gulf of Alaska.
The summer of 2009 had a number of distinct features including height anomalies associated with a predominantly negative NAO and AO while an El Nino built in the equatorial Pacific. The top analogs for the observed H5 pattern were 1950, 1951, 1958, 1960, 1965, 1977, 1982, 1985, 1998, and 2004. Filtering for the prefered ENSO conditions (details below), the list is condensed to 1951, 1958, 1965, 1977, 1982, and 2004.
Pacific:
Between April and June, SSTs in the equatorial Pacific warmed rapidly triggering a lot of "strong" El Nino talk. However, in late June, trade winds strengthened over the eastern Pacific, subduing the high SST anomalies. There have been multiple west wind pushes west of the dateline, but propogation into the western hemisphere has been minimal.
So what we've seen is a stall in the warming of the EPAC while central Pacific SSTs have been on the increase. At the start of September, the highest totals were located between 160E and 180. SST anomalies have the greatest effect in the western Pacific where totals are the highest and the exponential relationship between saturation vapor pressure and temperature dictates that evaporation rates are increased significantly with small deviations in SST. The west-based versus east-based argument matters with respect to where forcing is positioned, so even though SST anomalies may be slightly higher at times in the east Pacific, their effects are not as great and the anomalies near the dateline will have much more significance. Overall, I expect this El Nino episode to at least remain within the moderate threshold.
The convergence of the trade wind anomalies with the westerly wind bursts has provided focus for tropical convection, and we have seen this summer a number of OLR minimas just west of the dateline. Also, it should be noted that the summer analog composites display this well too.
In the north Pacific, there has been notable cooling near and south of the Aleutians. The -PDO has weakened to it's highest state since September 2007. However, at the same time, SST anomalies have cooled in the Gulf of Alaska. This has influence over the location of a trough over the north Pacific. It is clear that the north Pacific pattern will be a crucial battle ground this winter.
Atlantic:
SST anomalies in the north Atlantic have been tilted squarely toward a winter +NAO configuration. Using a regression with the two regions of interest yields a DJF NAO of +.85. However, the equatorial Atlantic is looking more favorable. There has been a general cooling of waters between Africa and South America. This should have overall weakening effect of the Atlantic hadley.
In addition, with primary tropical forcing occurring near the dateline, and some weaker forcing through the eastern Pacific, this forces an equatorial cell with sinking air over South America which again, weakens the Atlantic Hadley, and assists in the development of a -NAO.
Stratosphere:
Stratospheric easterly wind anomalies continue to make their descent, and the QBO took a steep dive this summer. Easterlies will continue to descend this winter, and the QBO will likely bottom out sometime in the spring. The descending, negative phase along with a warm ENSO period is highly supportive of a weakened polar vortex.
Preliminary Outlook:
There are definitely inconsistencies between each analog. I do not intend on using them directly, rather just as guidance for the outlook. Overall, there is a decent consensus for a dominant +NAO in December, a transition phase in January, and a dominant -NAO from late January through February. January and February could certainly feature a couple major winter storms in the eastern US. One significant x-factor is the North Pacific pattern. I think we will see the PDO become more neutral toward the winter, but another question is what happens with SSTs in the Gulf of Alaska.
Sunday, September 6, 2009
Beautiful weather to continue
The streak of sunny dry days will continue this week. Strong high pressure over the region and northward will suppress disturbances to the south. Daytime highs will reach the 70's with lows in the 40's to low 50's.
I have been away from the site for a little while with college starting, but I hope to continue a steady stream of updates (as the weather warrants).
To start, I have been working on my winter 2009-10 seasonal outlook which I hope to post by September 15th.
I have been away from the site for a little while with college starting, but I hope to continue a steady stream of updates (as the weather warrants).
To start, I have been working on my winter 2009-10 seasonal outlook which I hope to post by September 15th.
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