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9/30-10/5 Joaquin-Trough Interaction-DISCUSSION/OBS


bluewave

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The NAM completely shreds what is left of Joaquin and sends the moisture stream NW towards the coast. Closed low over the AL/GA border by Thursday afternoon with a negatively tilted trough quickly absorbing all of the 500mb vorticy like a vacuum. That in turn drives the development of several surface lows which move Northward and dump on us. 

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Hi-res NAM basically has scattered showers for our area and the real rain is well north. From Central CT to Maine.

 

If the 12z Rgem/GFS follow suit, this initial event will be just scattered convection.

It has more or less been like this for the past day. I was holding onto hope because the 00z GGEM, 00z RGEM and even the 00z ECWMF were rather wet for us tonight. Inland areas will see substantial rain tonight. It's a bit more of a crap shoot for the coast.

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The NAM completely shreds what is left of Joaquin and sends the moisture stream NW towards the coast. Closed low over the AL/GA border by Thursday afternoon with a negatively tilted trough quickly absorbing all of the 500mb vorticy like a vacuum. That in turn drives the development of several surface lows which move Northward and dump on us. 

it's interesting, if this scenario occurs, we get epic rains.  If the hurricane scenario unfolds, more potential for wind but the big rains will be in a more narrow corridor.

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Average precip. for NYC on the latest 4 runs of the GFS is 220mm or about 9".    The highest is 14" and the lowest 6.5"  Output was erratic:     80mm  340mm   300mm  160mm

There are convective elements involved as well as tropical connections from the Gulf and the area associated with Joaquin. PWAT's are in the 1.80"-2.00" range for the next several days. Assuming that Joaquin doesn't end up going out to sea, I would take the over on precip totals.

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DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 1100 AM EDT (1500 UTC), the center of Tropical Storm Joaquin was
located near latitude 26.5 North, longitude 70.8 West. Joaquin is
moving toward the west near 5 mph (7 km/h), and this general motion
is expected to continue for the next 48 hours.

Maximum sustained winds have increased to near 45 mph (75 km/h)
with higher gusts. Some strengthening is forecast during the next
48 hours.


Tropical storm force winds extend outward up to 70 miles (110 km)
from the center.

The estimated minimum central pressure is 1001 mb (29.56 inches).

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Every model has a dry slot for tomorrow. The rain tonight is associated with a surface low coming out of the TN valley and moving Northeast. Then we get a break until tomorrow night.

 

Just looking at those sim maps of the Rgem, the real maps will likely have under 1" of rain for our area.

A huge cut to yesterday's model consensus of 2"-4".

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Just looking at those sim maps of the Rgem, the real maps will likely have under 1" of rain for our area.

A huge cut to yesterday's model consensus of 2"-4".

The HRRR continues to show rain overspreading the area by late afternoon or early evening. I'm honestly not worried about it at all. Too much moisture and other elements involved not to get rain tonight. 

 

Just look at how strong the 700mb forcing is overnight.

 

NAM_CritThickRH_ne_f19.png

 

Sometimes I think models during the warm season tend to focus too much on convective maxima rather than the large scale elements in place. 

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TROPICAL STORM JOAQUIN DISCUSSION NUMBER 7

NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015
ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EDT TUE SEP 29 2015

1100 AM EDT TUE SEP 29 2015

Visible satellite imagery this morning shows that the cloud pattern
of the tropical cyclone is somewhat better organized than it was 24
hours ago. The low-level center is situated near the northern side
of the main area of deep convection due to northerly shear. The
upper level outflow is well defined over the southern semicircle of
the system, and restricted over the northern part of the
circulation. The current intensity is conservatively set at 45 kt,
which is a little below the latest Dvorak estimates. An Air Force
plane will be investigating Joaquin in a few hours, and should
provide a better estimate of intensity.

Based on the satellite center fixes, the initial motion continues
to be slowly westward, or 260/04 kt. The forecast track in
this advisory attempts to reconcile large model spread with an
overall shift toward the southwest of the previous track through 72
hours. Joaquin is currently in a relatively weak steering pattern,
but a building shortwave ridge in the northwestern Atlantic should
allow the cyclone to drift west and then west-southwestward. This
pushes the storm in the direction of the Bahamas, but the
deterministic and ensemble model consensus still shows a good
likelihood that Joaquin will stop fairly well short of the Bahamas,
and then begin accelerating to either the north or northeast. The
00Z ECMWF made a closer approach to the Bahamas, but it too turns
the storm sharply and accelerates it back into the Atlantic beyond
72 hours. The official forecast is to the left of the previous
forecast through 72 hours, and significantly slower at 4 and 5
days. It should be repeated that the confidence in the track
forecast is very low.

The vertical shear is predicted by the dynamical models to decrease
in 1 to 2 days. This should allow for additional strengthening,
which is reflected in the official forecast. The NHC wind speed
predictions may be conservative, since some of the guidance suggests
that Joaquin could become a hurricane in a few days.

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12z RGEM totals are out and AG3 was correct, they aren't pretty. Doesn't mean it's correct. The 00z RGEM was showing widespread 3-5" totals 12 hours ago. 

 

Verbatim, the 12z Rgem is now only .50"-1" for most of NJ and NYC.

What a terrible job by the models yesterday and through 0z last night.

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Verbatim, the 12z Rgem is now only .50"-1" for most of NJ and NYC.

What a terrible job by the models yesterday and through 0z last night.

Good lesson for all of us. 5 inches in a day is historic, it doesnt happen much and we should be wary when we see models spitting out that much more than 12 hours out.

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Verbatim, the 12z Rgem is now only .50"-1" for most of NJ and NYC.

What a terrible job by the models yesterday and through 0z last night.

We still have the rest of the 12z suite to get through. Secondly, how many times have we seen in the past that areas hit hard early on typically miss out the second time around? Maybe this one goes NW and we make up for it the next three days.

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We still have the rest of the 12z suite to get through. Secondly, how many times have we seen in the past that areas hit hard early on typically miss out the second time around? Maybe this one goes NW and we make up for it the next three days.

would like to see something over-perform for once...everything last 2 months has largely busted below forecast

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The 12z GFS is a bit southeast so far with the rains for tonight as compared to 06z. Noise, but like I said all of the elements are there. The heaviest rains might be with a convective max tonight, but that doesn't mean the rest of the area is dry either. Still a chance that convective max hits NW areas.

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Looks like the NHC has shifted the 5 day track further to the east and slowed it down alot. At least it looks east when comparing to earlier track!!!!!!!

hurricane models show a jog east, and then back NW later in time.  Definitely much slower by about 2 days.  The jog east to me at least would argue for a more northern impact as it will have a wider arc (should it be a stronger storm of course-if it doesnt develop then it doesnt matter)

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hurricane models show a jog east, and then back NW later in time. Definitely much slower by about 2 days. The jog east to me at least would argue for a more northern impact as it will have a wider arc (should it be a stronger storm of course-if it doesnt develop then it doesnt matter)

If there's a blocking ridge to the east, Joaquin will only get so far before it has to turn back. Depending on the strength of that ridge, Joaquin could make a sharp turn back. Sandy, which was a huge system, did just that. I'm thinking the rain later today largely hits the Appalachians along the path of the frontal wave, but that doesn't mean nothing for the Tri State.
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This is exacty why we need to stop comparing everything to Sandy. Basically every option is still on the table.

As far as handling 5" of rain we did it in my town in 2 hours with the last big event. There was flooding but only in the usual places like under overpasses. Best case it rains over an extended period in order to really soak in

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