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Tropical Global Model Runs Discussion 2017

In the western ATL basin during 10/4-9, today's 0Z EPS wasn't as active as yesterday's 12Z EPS though it still had notable activity:

Out of 50 runs, 9 (18%) were Hs vs 10 the prior run and 9 two runs ago. 3 hit W FL as Hs 10/7-8, 2 hit the Bahamas 10/7-9, 1 hit MS/AL 10/7, 1 hit LA 10/9, and the other 2 were still in the middle of the GOM moving slowly N/NW at the end of the run (10/10). I counted ~15 (~30%) TS+ vs ~22 (~44%) TS+ the prior run and ~15 (~30%) TS+ two runs ago.
 
At hour 216, the 12Z Euro develops a NW Caribbean surface low that moves NNW to just south of west central Cuba at hour 240.
 
The 11-15 day 12Z EPS is quite active and more active than the 0Z EPS in the western Caribbean/Gulf! More details to come once I've had time to examine the individual members. I can already tell you that the 240 hour 12Z EPS has many members with a low between 1004 and 1000 mb in the W Caribbean similar to the 12Z Euro op.
 
12Z EPS 50 members: the most active yet

Hurricanes: 13 H (26%) vs 9, 10, 9 three prior runs; 5 of the 13 H hit W FL 10/8-10 (panhandle or SW peninsula) while 3 others are threatening out in the Gulf to hit W FL ~10/11-2. 1 of these SW FL hits later hits NC as a H. Other 5 Hs: 2 hit SC and 3 move NE offshore the SE US while a H

TS+: ~25 of 50 or ~50% vs 30%/44%/30% prior 3 runs

Primary movement: genesis W Caribbean or S GOM with initial movement NW to N followed by turn to NE into NE GOM/FL or S of FL to offshore SE US though 2 of those curve back into SC
 
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GaWx said:
12Z EPS 50 members:

Hurricanes: 13 H (26%) vs 9, 10, 9 three prior runs; 5 of the 13 H hit W FL 10/8-10 (panhandle or SW peninsula) while 3 others are threatening out in the Gulf to hit W FL ~10/11-2. 1 of these SW FL hits later hits NC as a H. Other 5 Hs: 2 hit SC and 3 move NE offshore the SE US while a H

TS+: ~25 of 50 or ~50% vs 30%/44%/30% prior 3 runs

Primary movement: genesis W Caribbean or S GOM with inital movement NW to N followed by turn to NE into NE GOM/FL or S of FL to offshore SE US though 2 of those curve back into SC
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Well, it sounds like TCG is coming in the next week or so. I expect the numbers to keep climbing up as we get closer. It is getting to be that time of year. What worries me is that untapped region between the Yucatan and Cuba.The potential for a monster is there.
atlpot.png
 
GaWx said:
12Z EPS 50 members: the most active yet

Hurricanes: 13 H (26%) vs 9, 10, 9 three prior runs; 5 of the 13 H hit W FL 10/8-10 (panhandle or SW peninsula) while 3 others are threatening out in the Gulf to hit W FL ~10/11-2. 1 of these SW FL hits later hits NC as a H. Other 5 Hs: 2 hit SC and 3 move NE offshore the SE US while a H

TS+: ~25 of 50 or ~50% vs 30%/44%/30% prior 3 runs

Primary movement: genesis W Caribbean or S GOM with initial movement NW to N followed by turn to NE into NE GOM/FL or S of FL to offshore SE US though 2 of those curve back into SC
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Working too much on this end (which is a good thing) - Thanks, Larry, for the continued updates. Without them I'd be lost! If you see anything ominous before the 9th, please PM me with a heads-up!
Best!
Phil
 
pcbjr said:
Working too much on this end (which is a good thing) - Thanks, Larry, for the continued updates. Without them I'd be lost! If you see anything ominous before the 9th, please PM me with a heads-up!
Best!
Phil
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YW. The 12Z EPS says that ~80% of the 25 members that become a TS+ hit the CONUS from the Gulf (centered on FL from Panhandle south to south tip/Keys) while most of the other 20% slip just SE of S FL while moving NE. A few curve back into the SE coast, mainly SC/NC. I saw virtually none that went west and got buried in Central America.

The highest threat period is 10/6-12. So, we may be following this potential threat for quite a long time should it materialize.
 
GaWx said:
I'm going to restate what I have been saying about western ATL basin TC genesis/development GEFS biases in case some are not following what I'm saying:

- the 18Z GEFS has day after day been the most active GEFS run BY FAR. A theory has been presented at Storm 2K that this is due to 18Z being the time of max solar insolation in/near the western ATL basin.
- the 6Z GEFS has day after day been the least active GEFS run BY FAR.
- the 0Z/12Z GEFS have been in between the surrounding 18Z/6Z GEFS every time.

With a repeating pattern like this, there are obvious biases that need to be considered when looking at each GEFS run as randomness definitely doesn't explain this. When I see the 18Z GEFS, I assume it is too active. When I see the 6Z GEFS, I assume it is too quiet. The 0Z/12Z GEFS seem to be the most reasonable to me of the 4 runs since they're in between.
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Yeah, I've noticed that watching winter threats. Someone always throws out the "no statistical difference line" but I've noticed that 6z will always be weaker and less precip and 18z is the weenie run.
 
Arcc said:
Yeah, I've noticed that watching winter threats. Someone always throws out the "no statistical difference line" but I've noticed that 6z will always be weaker and less precip and 18z is the weenie run.
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Interesting! I never realized this. I used to think that the "We toss" the 18Z was just to be silly. Not anymore! Speaking of which, it wouldn't be Happy Hour without the presentation of the drunk (thank you Chris for inspiring the use of the word drunk for models) 18Z GEFS. It is no surprise that it is the most active GEFS in the W Caribbean/Gulf since the prior 18Z though it doesn't get really active til days 13-16. I counted about 40% of the members with a hurricane and the vast majority of members with at least a TS. Oh, 18Z GEFS, you really must love the attention!
 
GaWx said:
Interesting! I never realized this. I used to think that the "We toss" the 18Z was just to be silly. Not anymore! Speaking of which, it wouldn't be Happy Hour without the presentation of the drunk (thank you Chris for inspiring the use of the word drunk for models) 18Z GEFS. It is no surprise that it is the most active GEFS in the W Caribbean/Gulf since the prior 18Z though it doesn't get really active til days 13-16. I counted about 40% of the members with a hurricane and the vast majority of members with at least a TS. Oh, 18Z GEFS, you really must love the attention!
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I think there probably isn't much difference in verification with tracks, but the other things I've mentioned definitely are different. I can't tell you how many times I've rode the coaster up from 12z to the 18z weenie run, the down slightly to the 0z run and then heartbreak on the 6z run to only start over a few hours later.
 
GFS tries a bit of east coast of Florida development this run, while the CMC has a storm in the gulf in a few days. The NAM at 6Z had a low around there too. May be worth watching.
Meteorologist1999 said:
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Beware For Stalling Fronts off the SE COAST!!!
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This seems to be the area the GFS wants to develop something, though no official NHC TWOs mention it.
 
^ Today's 12Z was a really strange Euro run. It has 3 teeny weeny lows from and move westward into FL 10/1-3. It also has a broader 1012 mb surface low coming in westward to near Fort Pierce around hours 108-114. So, there are 4 different small sfc lows coming westward into FL between 9/30 and 10/3 and then moving out into the Gulf! They all form underneath the big high that camps out over the NE US. This illustrates that being south of a strong surface high often is conducive for a low to form to the south of the high (due to low level convergence causing air to pile up and thus rise). None of them may ever amount to much tropically due to shear. Most likely none of them will become a TC. However, this Euro along with the recent GFS/CMC runs is a reason that the SE US coast, especially FL, should monitor the area just east of FL for surprise tropical mischief just in case.

Even without tropical development, the Euro is showing nonstop strong onshore winds 10/1-4 for the SE US with the strongest centered on NE FL/SE GA. This run has winds just offshore as high as 40 knots just to the north of some of these microlows due to pinching of the gradient. Onshore winds actually continue into 10/6. The Euro may very well be overdone. Regardless, I'm becoming concerned about is coastal flooding near high tides in the CHS-St. Augustine corridor, especially around the full moon 10/4-6, as well as rip currents 10/1-4.

Edit: The 18Z GFS fwiw has onshore winds, sometimes strong, for the SE US coast from CHS southward through FL nonstop 10/1-12! This run may be overdoing things, but the idea of many days in a row of onshore winds has been showing up on a good number of model runs of various models. The highest astronomical tides of the month are 10/6-10, near and just after the full moon. This is something that coastal flooding vulnerable SE coasters might want to keep in the back of their head, especially CHS to St. Augustine.
 
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Folks,
The 00Z GFS has a weak surface low form along a stationary front over Sofla on Friday. Then it moves on Saturday NE to ~100 miles E of Melbourne, where it stalls. Then it moves back SW to Sofla on Sunday followed by a westward move into the Gulf on Monday. It remains weak the entire time.

The CMC (take with a huge grain) has a low form just n of W Cuba on Friday followed by a move NE to just off SW FL, where it stalls and becomes a TC on Saturday. Then on Sunday it moves westward out into the Gulf as a TS and reaches N MX late on Tuesday.
 
An area of disturbed weather associated with a trough of low
pressure is located over the northwestern Caribbean Sea. This
system is forecast to move slowly north-northwestward across Cuba
and the Straits for Florida during the next day or so. Some
development of this system is possible when it moves near the
Florida peninsula or the northwestern Bahamas on Friday or Saturday
before upper-level winds become less favorable early next week.
Regardless of development, this system is likely to produce locally
heavy rainfall over portions of Cuba, southern Florida, the Florida
Keys, and the Bahamas during the next several days.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...20 percent.
 
Meanwhile we have this at the end of the 12z euro something else entirely(probably related to the w Carib development the lr gfs has hinted at )
received_1534674223282562.png
 
Storm5 said:
12z eps is very excited
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Further to this: the 12Z EPS has a whopping 16 hurricanes from the 50 members or 32% of them, which is 3 more than any previous run! Also, keep in mind that the EPS members are supposedly run at a lower resolution than the operational meaning SLPs can easily be underdone. Of these 16, 5 hit western FL (Panhandle to Keys/Naples) 10/7-12, 1 hits S TX 10/6, and 1 hits eastern Long Island, NY 10/8.
 
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