It seems like we have been talking about the Heather A signal for some time. To refresh the memory a Heather A signal is when the teleconnectors are showing a rise from a very negative NAO to a positive NAO and how this usually signals a large storm along the east coast. For more information do a google search on Heather Archambault.
Some of the guidance last night was indeed picking up on the signal and showing the signal ..while some of the guidance almost seemed as if it was lost to what the other guidance was showing.
We are going to start with the guidance that seems to be on one side of the camp..That would be the 00z GFS/GGEM
You can see the GFS above at 144 hrs. While it does show a storm system along the east coast..it completely fails to phase and so we continue to end up with a disorganized and weak storm system that would bring some moderate rains across vast majority of the region.
At 12 Z today the GFS does still have a low pressure off the coast but again the way it gets to this location is completely different from the guidance from last night. This does not mean it can not be correct it just means that right now it would be a low probability scenario outcome.
The GGEM last night stood out in even more contrast as it does not even have a system on or near the coast.
The system it has is well out to sea. Again, this does not mean it could not be correct but with the Heather A signal it would also be very low probability.
Lets move on to the more interesting of the 00z guidance and the next two would suggest a Massive Flooding rain event across a good portion of the region. That would be the UKMET/NOGAPS
Now that storm on the UKMET one could say is indeed impressive. This storm on the UKMET could possibly rival the Superstorm of 1993. Needless to say the UKMET is probably on the deepest side of the solution envelope. This would like mentioned cause some Massive Flooding issues and I am pretty positive some severe weather outbreak as well across the region.
00z Nogaps also shows another system that would lead to some very heavy rains with flooding potential as it is quite warm with the solution it is showing. Remember we are dealing with a coastal system here so seeing the NOGAPS in this position becomes important when looking at other guidance like the GGEM for example with it being OTS.
Now what the UK/NOGAPS have in common is they are both showing a very powerful Nor”easter type storm system that one would generally expect when there is a Heather A signal. So one has to lean more towards that camp at this present time.
Now what about the ECM? Where does this model fall as of 00z? Well the ECM is probably the most impressive of all the guidance if you are looking for snowfall.
980 MB just off the coast of NYC. The ECM actually develops this storm over the GOM & SE and then moves it up along the coast as it is deepening.
The ECM for some parts of the region , even down towards but not quite in PHL would more then likely be a heavy wet snow.
For example the soundings look like this at ABE:
FRI 12Z 01-APR 1.4 -0.5 1003 94 100 0.42 543 541
FRI 18Z 01-APR 0.9 -3.2 990 90 91 0.81 533 542
SAT 00Z 02-APR 0.7 -4.8 988 90 95 0.33 526 535
SAT 06Z 02-APR 0.4 -5.0 991 84 91 0.11 527 534
The above is for ABE
Total QPF 1.67
Surface temps 32-34.5
So, as of 00z last night we can place the ECM in the same camp as the UK/Nogaps.
These three models suggest a Potent and powerful storm will effect the east coast. We will monitor the rest of the 12 Z guidance and update this later this afternoon.
We still feel the potential exists for a powerful storm system to effect the east coast in this time range. Potentially heavy rains in the warm sector and heavy snows in the cold sector.
Stay tuned for more updates.
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