Isotherm Posted August 21, 2012 Share Posted August 21, 2012 Comments-discussion-questions welcome http://www.lightinthestorm.com/ With summer nearly in the record books, the first month of meteorological autumn is just ahead. September promises to bring shorter days, longer, cooler nights, and bit less humidity – that we can be certain of! However, will the month average out warmer than normal or cooler than normal? Pattern persistence argues for a continuation of the mild regime across much of the United States, as we’ve seen higher than avg temp departures for most of the past 12-16 months. Over the last 1-2 weeks, there has been noticable changes in the pattern, with significant cooling into the Mid-west and Plains states. That coolness has attempted to propagate east, and has succeeded to bring temperatures down to near/slightly below normal levels in the Northeastern states. With that being said, the remainder of this week into the weekend will feature gradually climbing temps, but still within the normal range (about 83-88F). The West Atlantic ridge has been strong and very resistant to cold fronts on its western periphery. The NAO/AO have been negative all summer — plentiful blocking in the northern hemisphere. However, due to the enormous amount of warmth across North America, the high latitude blocking has only managed to create pockets of negative temp anomalies. Additionally, blocking in summer-September can yield a much different pattern than during the cold season. For example, over the coming weeks, the NAO is likely to stay neutral to negative, but it’s probable that it will connect w/ the West Atlantic ridge, keeping the East Coast on the mild side. The AO looks to neutralize in the medium range, possibly jumping positive into September, while PNA values should be positive as we begin September. What does all this mean? I think it’s important to examine similar years in the past to form an opinion about what may happen in our future. The 1950s parallel the current year quite well, due in part to the warm Atlantic and cool Pacific ocean phase we’re currently experiencing. When we throw in the variables of ENSO state and other teleconnection modality, we can form a more accurate picture of the potential weather pattern. Given the oncoming El Nino (readings are now +0.6c in region 3.4 indicative of weak Nino criteria), the years 1951, 1957, and 2002 are of particular interest. 1951 was an analog that I utilized for this summer, and it seemed to work well in predicting the overall warmth across America. 1958 and 1953 are two other analogs which fit the current and forecast regime into mid September. The analog package paints the following picture for temperature anomalies in North America: A closer look at the United States temp departure forecast vas per the analogs: Note that the mean trough is probable to position itself in the Upper Mid-west/Great lakes, with positive heights in the West and East. As an aside, this pattern is one that may be conducive for tropical cyclone activity (direct or indirect influence) in the Southeastern US, and up the East Coast. Forecasting a cyclone in the Northeast is like throwing a dart blindfolded, but one can say that the pattern is more favorable than normal for direct or indirect effects — maybe remnants. If we take a look at the analog precip forecast, it suggests a wet SE US, but not so much in the Northeast. Maybe indicative of recurving cyclones. The NAEFS suggests a warm East coast pattern will ensue in the medium range: All in all, it appears likely that the warmer than average pattern will continue for another month in the Northeast. My guess would be +1 to +2 in NYC for temperatures (slightly warmer than what August will finish at). The Mid-west is the one region of the country that may experience a cooler than normal September. Precipitation should be above average in the Southeast (tropical activity), with slightly below avg precip in the NYC-NE corridor. It’s too early to say whether Isaac will have any impact up here; however, the pattern is more conducive than usual for an East Coast hit. More likely, we’ll see remnants from Isaac, after it hits the Eastern Gulf or Southeast States. Link to comment Share on other sites More sharing options...
psv88 Posted August 22, 2012 Share Posted August 22, 2012 Comments-discussion-questions welcome http://www.lightinthestorm.com/ With summer nearly in the record books, the first month of meteorological autumn is just ahead. September promises to bring shorter days, longer, cooler nights, and bit less humidity – that we can be certain of! However, will the month average out warmer than normal or cooler than normal? Pattern persistence argues for a continuation of the mild regime across much of the United States, as we’ve seen higher than avg temp departures for most of the past 12-16 months. Over the last 1-2 weeks, there has been noticable changes in the pattern, with significant cooling into the Mid-west and Plains states. That coolness has attempted to propagate east, and has succeeded to bring temperatures down to near/slightly below normal levels in the Northeastern states. With that being said, the remainder of this week into the weekend will feature gradually climbing temps, but still within the normal range (about 83-88F). The West Atlantic ridge has been strong and very resistant to cold fronts on its western periphery. The NAO/AO have been negative all summer — plentiful blocking in the northern hemisphere. However, due to the enormous amount of warmth across North America, the high latitude blocking has only managed to create pockets of negative temp anomalies. Additionally, blocking in summer-September can yield a much different pattern than during the cold season. For example, over the coming weeks, the NAO is likely to stay neutral to negative, but it’s probable that it will connect w/ the West Atlantic ridge, keeping the East Coast on the mild side. The AO looks to neutralize in the medium range, possibly jumping positive into September, while PNA values should be positive as we begin September. What does all this mean? I think it’s important to examine similar years in the past to form an opinion about what may happen in our future. The 1950s parallel the current year quite well, due in part to the warm Atlantic and cool Pacific ocean phase we’re currently experiencing. When we throw in the variables of ENSO state and other teleconnection modality, we can form a more accurate picture of the potential weather pattern. Given the oncoming El Nino (readings are now +0.6c in region 3.4 indicative of weak Nino criteria), the years 1951, 1957, and 2002 are of particular interest. 1951 was an analog that I utilized for this summer, and it seemed to work well in predicting the overall warmth across America. 1958 and 1953 are two other analogs which fit the current and forecast regime into mid September. The analog package paints the following picture for temperature anomalies in North America: A closer look at the United States temp departure forecast vas per the analogs: Note that the mean trough is probable to position itself in the Upper Mid-west/Great lakes, with positive heights in the West and East. As an aside, this pattern is one that may be conducive for tropical cyclone activity (direct or indirect influence) in the Southeastern US, and up the East Coast. Forecasting a cyclone in the Northeast is like throwing a dart blindfolded, but one can say that the pattern is more favorable than normal for direct or indirect effects — maybe remnants. If we take a look at the analog precip forecast, it suggests a wet SE US, but not so much in the Northeast. Maybe indicative of recurving cyclones. The NAEFS suggests a warm East coast pattern will ensue in the medium range: All in all, it appears likely that the warmer than average pattern will continue for another month in the Northeast. My guess would be +1 to +2 in NYC for temperatures (slightly warmer than what August will finish at). The Mid-west is the one region of the country that may experience a cooler than normal September. Precipitation should be above average in the Southeast (tropical activity), with slightly below avg precip in the NYC-NE corridor. It’s too early to say whether Isaac will have any impact up here; however, the pattern is more conducive than usual for an East Coast hit. More likely, we’ll see remnants from Isaac, after it hits the Eastern Gulf or Southeast States. As usual, awesome writeup and analysis. The warm trend continues... Link to comment Share on other sites More sharing options...
Isotherm Posted August 22, 2012 Author Share Posted August 22, 2012 As usual, awesome writeup and analysis. The warm trend continues... Thanks man; let's hope the warm trend ends before this winter. My ideal scenario would be cold from October-April ala 1977. Link to comment Share on other sites More sharing options...
easternsnowman Posted August 22, 2012 Share Posted August 22, 2012 +1 to + 2 is about normal for the past 10 years or so for sept. Link to comment Share on other sites More sharing options...
Isotherm Posted August 22, 2012 Author Share Posted August 22, 2012 +1 to + 2 is about normal for the past 10 years or so for sept. For the 2001-2011 period, you'd be correct. Temp departures about +1 to +2, so this September should be fairly similar to the 2000-2011 average if my forecast verifies. Link to comment Share on other sites More sharing options...
SACRUS Posted August 22, 2012 Share Posted August 22, 2012 Sep departues: Year....EWR / NYC 2011: +3.0 / +2.0 2010: +3.4 / +3.1 2009: -1.3 / -1.7 2008: +1.3 / +0.8 2007: +1.9 / +2.3 2006: -1.6 / -1.4 2005: +5.3 / +5.3 2004: +1.4 / +1.3 2003: +0.4 / -0.1 2002: +2.2 / +2.2 2001: -0.8 / -0.4 2000: -1.8 / -2.0 1999: +1.1 / +1.0 Link to comment Share on other sites More sharing options...
SACRUS Posted August 22, 2012 Share Posted August 22, 2012 Nice writeup Iso as always. Forecast looks good. I wouldnt mind a blend of 2005 and 2010, but think the month will end closer to 2002 with +2 range. I still think we ride above precip as well. Link to comment Share on other sites More sharing options...
uncle W Posted August 22, 2012 Share Posted August 22, 2012 nice post...Here are September averages from my fall climate post... September decade averages... Decade...ave temp...rainfall...ave max...ave min... 1870's......65.3......3.41"............................ 1880's......66.2......4.18"......86.5......46.1 1890's......67.7......3.38"......89.6......47.0 1900's......68.1......3.84"......86.8......48.4 1910's......66.8......3.09"......89.5......45.6 1920's......67.8......3.54"......91.1......47.2 1930's......68.7......5.15"......90.0......47.9 1940's......68.8......3.70"......91.2......45.5 1950's......68.3......2.36"......89.9......45.6 1960's......67.7......3.85"......90.2......47.2 1970's......68.3......4.73"......90.1......47.1 1980's......68.6......3.58"......90.3......47.5 1990's......68.0......4.18"......88.7......47.6 2000's......68.6......4.91"......86.5......49.7 2010's.....70.6.......6.53"......91.0......52.5 1870- 2009........67.8......3.85"......89.2......47.1 1980- 2009........68.4......4.22"......88.5......48.3 Link to comment Share on other sites More sharing options...
Sundog Posted August 22, 2012 Share Posted August 22, 2012 September 2005 was probably the most uncomfortable one I've ever experienced. Link to comment Share on other sites More sharing options...
easternsnowman Posted August 22, 2012 Share Posted August 22, 2012 I also believe we will be on the dry side unless (which is very possible) that tropical systems come our way. Link to comment Share on other sites More sharing options...
forkyfork Posted August 22, 2012 Share Posted August 22, 2012 if isaac goes into the gulf as a strong system, we might get an impressive surge of warmth... see the 0z euro Link to comment Share on other sites More sharing options...
ag3 Posted August 22, 2012 Share Posted August 22, 2012 if isaac goes into the gulf as a strong system, we might get an impressive surge of warmth... see the 0z euro Yeah. Isaac basically pushes the ridge northeastward and dumps major heat across the entire country days 8-10 and beyond. Easy 95+, if the euro were to verify. Link to comment Share on other sites More sharing options...
easternsnowman Posted August 22, 2012 Share Posted August 22, 2012 Yeah. Isaac basically pushes the ridge northeastward and dumps major heat across the entire country days 8-10 and beyond. Easy 95+, if the euro were to verify. Alot of if's involved, everything will have to go perfectly for that to happen. We should'nt want it to go to the gulf anyway.......... with the oil rigs out there, talk about gas prices now!! Link to comment Share on other sites More sharing options...
Isotherm Posted August 22, 2012 Author Share Posted August 22, 2012 Nice writeup Iso as always. Forecast looks good. I wouldnt mind a blend of 2005 and 2010, but think the month will end closer to 2002 with +2 range. I still think we ride above precip as well. Thanks, and yeah I was less confident on the pcpn aspect of the forecast. The big key is the amount of impact direct/indirect we'll have w/ tropical cyclones. If Isaac goes into the Gulf, then MS Valley, we won't see much of anything. Once we hit September, with the T-storm season beginning to die down, tropical remnants often provide a healthy percentage of our rainfall. Of course it's too early to say we'll have any impact. Forecasting a TC up the east coast is probably one of the more difficult calls to make. I agree with the 2002 look, temps near +2. Link to comment Share on other sites More sharing options...
Isotherm Posted August 22, 2012 Author Share Posted August 22, 2012 nice post...Here are September averages from my fall climate post... September decade averages... Decade...ave temp...rainfall...ave max...ave min... 1870's......65.3......3.41"............................ 1880's......66.2......4.18"......86.5......46.1 1890's......67.7......3.38"......89.6......47.0 1900's......68.1......3.84"......86.8......48.4 1910's......66.8......3.09"......89.5......45.6 1920's......67.8......3.54"......91.1......47.2 1930's......68.7......5.15"......90.0......47.9 1940's......68.8......3.70"......91.2......45.5 1950's......68.3......2.36"......89.9......45.6 1960's......67.7......3.85"......90.2......47.2 1970's......68.3......4.73"......90.1......47.1 1980's......68.6......3.58"......90.3......47.5 1990's......68.0......4.18"......88.7......47.6 2000's......68.6......4.91"......86.5......49.7 2010's.....70.6.......6.53"......91.0......52.5 1870- 2009........67.8......3.85"......89.2......47.1 1980- 2009........68.4......4.22"......88.5......48.3 Interesting to note the temp maximum in the 30s-50s, cooler in the 60s/70s, then back up a bit in recent decades. Late 1800s had average Sept temps around 65, in those days Sept actually felt a good deal cooler than JJA... Link to comment Share on other sites More sharing options...
Isotherm Posted August 22, 2012 Author Share Posted August 22, 2012 September 2005 was probably the most uncomfortable one I've ever experienced. It was a torrid month for sure. Was running cross-country at the time so the heat felt 10X worse. High dews can often persist thru Sept into early Oct. Link to comment Share on other sites More sharing options...
forkyfork Posted August 22, 2012 Share Posted August 22, 2012 the 588 height contour lifts well to the N on the euro and its ens mean by the end of august http://www.ecmwf.int/products/forecasts/d/charts/medium/eps/ensm/essential!Geopotential%20at%20500hPa!North%20America!216!pop!od!enfo!plot_ensm_essential!2012082212!!/ Link to comment Share on other sites More sharing options...
Isotherm Posted August 22, 2012 Author Share Posted August 22, 2012 the 588 height contour lifts well to the N on the euro and its ens mean by the end of august http://www.ecmwf.int...l!2012082212!!/ Yeah, Labor day weekend has the potential to be a hot one. Probably our next chance for widespread 90s is end of Aug/early Sept. Link to comment Share on other sites More sharing options...
uncle W Posted August 22, 2012 Share Posted August 22, 2012 Interesting to note the temp maximum in the 30s-50s, cooler in the 60s/70s, then back up a bit in recent decades. Late 1800s had average Sept temps around 65, in those days Sept actually felt a good deal cooler than JJA... the 1940's has the warmest average temperature and monthly max...It also has the coolest monthly average minimum...The 2000's had the coolest average max and warmest average low...The 2010's continue the rise in the average minimum... Link to comment Share on other sites More sharing options...
easternsnowman Posted August 23, 2012 Share Posted August 23, 2012 Yeah, Labor day weekend has the potential to be a hot one. Probably our next chance for widespread 90s is end of Aug/early Sept. That may be our last chance and even if it gets hot it won't be the july type heat we had. Link to comment Share on other sites More sharing options...
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