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Rainshadow

February/March Meteorological Pattern Discussion.

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00z March 9th GEFS

Except for a continuous 30 hour interlude around Tuesday morning the 12th, above normal 500mb heights prevail into the 17th. (a day later than two days ago).   The developing +PNA pattern brings below normal heights on the 19th (same as two days ago) thru the 23rd (extending it two days longer). Flattening of PNA ridge returns near normal heights to the end of its run on the 24th.  EPO looks mainly positive and any -NAO looks -NAO east.

NAEFS for the week of 3/17-3/24 has our area surrounded by higher confidence of below normal temperatures.  Losing the 15th & 16th is tipping the scales colder.

MJO is in Phase 4.  Want to say eastern part of phase 3 ok.  Regardless of the silly GEFS (among others) WH outlooks phase 5 in March is colder in the northeast. Phases 6 & 7 are warmer.  So this PNA spike and cooler week has MJO support even if the WH outlooks are rofl as to where it thinks it is going.  Beyond that the relaxation makes sense as long as the MJO continues to progress at the same rate of speed. It does sometime slow in 5 & 6.  Just double checked the strat, and there isn't much going on with wave 1 or 2 hits, may be late in the game for them anyway.

 

00z March 11th GEFS

Strongly above normal 500mb heights peak March 12th-16th. Below normal 500mb heights try try try to get into the area on the 17th, but struggle to cover the entire area until the 20th.   BIAS corrected GEFS PNA index peaks on the 18th, but remains somewhat positive thrut as does a +NAO.  EPO returns to a more neutral index look, but I would say looks more positive than negative on the forecast maps.  Below normal heights exit on the 23rd (same as two days ago) as flattening of PNA ridge continues.  A tendency toward above normal heights concludes this run on the 25th & 26th as does a (ha) hint of a -NAO east.

NAEFS for the week of 3/19-3/26 has our area in high confidence of near normal temperatures.   This means either the 17th and/or 18th should be cold, or it was just a warmish modeling jump for a day (it looks like that).  Either way the 500mb tendency looks like a cold start/warmer finish.

MJO is in Phase 4.  Tossing the retrograding WH outlooks and assuming a phase 5 is coming, this corroborates the PNA ridge for next week.  Phases 6 & 7 are warmer.  So either entering the COD (doubt it very much) or exiting phase 5 support the end of the current GEFS/GEPS/EPS, slightly higher confidence than average for that forecast time range.  Warm week/cold week/warm week if all goes accoring to plan. :unsure2:

 

00z March 14th GEFS

Strongly above normal 500mb heights go bye bye on the 16th and get replaced by below normal until the 20th.  Same as three days ago.   Still positive PNA with an anomalous trof over the SERN Conus and outlooked offshore cyclogenesis as spring arrives. As PNA is outlook to flatten, above normal heights return on the 23rd. (+EPO/+NAO).  This overall pattern holds to the end of its run through the 29th.  There is either west coast or eastern pacific troffing and any hint of -NAO is -NAO east. 

NAEFS for the week of 3/22-3/29 has confidence of above normal temperatures in our area. This rolled over yesterday after losing cold I am guessing from the 20th & 21st.

MJO is in Phase 5 (or 4?).  It still looks pretty active and outlooks still have it going into the COD. But at least now they have it progressing vs the silly loop de loops into phase 3 they once had.  Mike's site outlopok for the last week of March are warm MJO phases for our area for March. So call me confident about a warmer than average send off to this Smarch.

 

00z March 18th GEFS

Positive PNA below normal 500mb heights last til the 20th and then come back with offshore/east development on the 21st thru 23rd.  As the +PNA ridging moves eastward across NOAM, above normal heights return on the 24th (one day later than the outlook from four days ago).  A negative NAO is outlooked to develop and heights return to near normal on the 26th. the long run of above normal heights gone. On the 26th there is the -NAO E and neutral looking PNA (maybe index positive) with trofs across the southwest & southeast CONUS. Latter with latest day 9 Euro snow.  As that SE trof exits, above normal heights briefly return on the 29th & 30th, +NAO at that point. Til the end of its run on April 2nd, we drift in/out of normal and slightly below normal heights with mainly a zonal flow.

NAEFS for the week of 3/26-4/2 has pretty high confidence of above normal temperatures. So much for the GEFS thoughts. EPS does not look that cold either.

MJO is in Phase 5.  COD location I am guessing because of 200mb winds, but convection still looks rather robust and that is what drives the latent heat release.  So warmer phases on the way until maybe a real COD after phase 6 or 7.  A warmer than average send off to Smarch still looks there.

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00z March 11th GEFS

Strongly above normal 500mb heights peak March 12th-16th. Below normal 500mb heights try try try to get into the area on the 17th, but struggle to cover the entire area until the 20th.   BIAS corrected GEFS PNA index peaks on the 18th, but remains somewhat positive thrut as does a +NAO.  EPO returns to a more neutral index look, but I would say looks more positive than negative on the forecast maps.  Below normal heights exit on the 23rd (same as two days ago) as flattening of PNA ridge continues.  A tendency toward above normal heights concludes this run on the 25th & 26th as does a (ha) hint of a -NAO east.

NAEFS for the week of 3/19-3/26 has our area in high confidence of near normal temperatures.   This means either the 17th and/or 18th should be cold, or it was just a warmish modeling jump for a day (it looks like that).  Either way the 500mb tendency looks like a cold start/warmer finish.

MJO is in Phase 4.  Tossing the retrograding WH outlooks and assuming a phase 5 is coming, this corroborates the PNA ridge for next week.  Phases 6 & 7 are warmer.  So either entering the COD (doubt it very much) or exiting phase 5 support the end of the current GEFS/GEPS/EPS, slightly higher confidence than average for that forecast time range.  Warm week/cold week/warm week if all goes accoring to plan. :unsure2:

 

00z March 14th GEFS

Strongly above normal 500mb heights go bye bye on the 16th and get replaced by below normal until the 20th.  Same as three days ago.   Still positive PNA with an anomalous trof over the SERN Conus and outlooked offshore cyclogenesis as spring arrives. As PNA is outlook to flatten, above normal heights return on the 23rd. (+EPO/+NAO).  This overall pattern holds to the end of its run through the 29th.  There is either west coast or eastern pacific troffing and any hint of -NAO is -NAO east. 

NAEFS for the week of 3/22-3/29 has confidence of above normal temperatures in our area. This rolled over yesterday after losing cold I am guessing from the 20th & 21st.

MJO is in Phase 5 (or 4?).  It still looks pretty active and outlooks still have it going into the COD. But at least now they have it progressing vs the silly loop de loops into phase 3 they once had.  Mike's site outlopok for the last week of March are warm MJO phases for our area for March. So call me confident about a warmer than average send off to this Smarch.

 

00z March 18th GEFS

Positive PNA below normal 500mb heights last til the 20th and then come back with offshore/east development on the 21st thru 23rd.  As the +PNA ridging moves eastward across NOAM, above normal heights return on the 24th (one day later than the outlook from four days ago).  A negative NAO is outlooked to develop and heights return to near normal on the 26th. the long run of above normal heights gone. On the 26th there is the -NAO E and neutral looking PNA (maybe index positive) with trofs across the southwest & southeast CONUS. Latter with latest day 9 Euro snow.  As that SE trof exits, above normal heights briefly return on the 29th & 30th, +NAO at that point. Til the end of its run on April 2nd, we drift in/out of normal and slightly below normal heights with mainly a zonal flow.

NAEFS for the week of 3/26-4/2 has pretty high confidence of above normal temperatures. So much for the GEFS thoughts. EPS does not look that cold either.

MJO is in Phase 5.  COD location I am guessing because of 200mb winds, but convection still looks rather robust and that is what drives the latent heat release.  So warmer phases on the way until maybe a real COD after phase 6 or 7.  A warmer than average send off to Smarch still looks there.

 

00z March 20th GEFS

Brief above normal 500mb heights until neg tilt trof (below) on the 21st.  As the +PNA ridging moves eastward across NOAM, above normal heights return on the 24th (same as two days ago).  A negative NAO E develops and heights return to near normal sooner on the 25th. Rockies PNA ridging/ -NAO E bring below normal heights to our period of interest late on the 25th.  Breakdown of the -NAO E/ PNA ridge brings above normal heights back on the 28th. This persists to the end of March. As Sapril starts a series of Pacific trofs bring an el nino look with below normal heights across the southern & southwestern conus. Our heights return to above normal on April 3rd & 4th (end of run).

NAEFS for the week of 3/28-4/4 is weakly confidence of above normal temperatures. 

MJO as far as convection goes is in Phase 5 almost phase 6.  The amount of convection and the 850mb & esp 200mb push into the COD.  The models were right (I was wrong) about it weakening. Although convection is not nil and any convective forcing would assist in warmer phase solutions going forward. I like the split of different MJO factors as convection still drives the ridging bus. Granted if there is not support aloft, it won't be easy going forward.

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Speaking of next week as far as teleconnections go, there has been a "negative GEFS bias" with all of them, especially at longer ranges:

 

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I reviewed the normalized monthly tabulated NAO index at CPC.  The NAO has averaged positive for 22 of the last 30 months.  Given the variety of teleconnections that influence our weather - MJO, PDO, AO, PNA, etc. - is there any statistical significance to be gained by this trend?  Or is it more information that is fed into modeling to be analyzed with the other teleconnections?  I feel as though recent weather discussions have de-emphasized the significance of a negative NAO on our weather.  Is this because the NAO has remained stubbornly positive or because the NAO was a teleconnection that was identified early and has now been supplanted, or rather joined, by myriad other influential teleconnections? 

I know meteorological science is constantly evolving.  Just trying to develop a greater understanding. TIA.

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