2015 Global model runs discussion

[srainhoutx]

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1046 AM EDT WED APR 29 2015

VALID 12Z SAT MAY 02 2015 - 12Z WED MAY 06 2015


USED A BLEND OF THE 00Z/29 NAEFS AND ECENS MEANS FOR THE LATEST
MEDIUM-RANGE MANUAL PROGS. THE ENSEMBLE MEANS--AND TO A LARGE
EXTENT, THE OPERATIONAL MODELS--ARE IN HARMONY WITH THE PREDICTED
FLOW ACROSS CENTRAL NORTH AMERICA THIS PERIOD. THE BIGGEST
DIFFERENCES LIE OVER THE WESTERN ATLANTIC, BOTH AT THE BEGINNING
AND END OF THE FORECAST. THE EUROPEAN CENTRE GUIDANCE IS STILL
FARTHER OFFSHORE WITH THE SPRAWLING CYCLONE DAY 3 THAN THE OTHER
MODELING CENTERS. SINCE THE BULK OF THE GUIDANCE IS A BIT WEST OF
THE EUROPEAN CENTRE, ELECTED TO INCORPORATE ONLY 30 PERCENT OF THE
MOST RECENT ECENS MEAN AS A PROBABILISTIC HEDGE. BY DAY 7, THE
00Z/29 GFS AND GDPS BOTH SPIN UP A SUBTROPICAL-LOOKING CIRCULATION
NEAR THE BAHAMAS. THE 06Z/29 GFS BACKED OFF THAT IDEA. THE
ENVIRONMENT LOOKS QUITE SHEARED/BAROCLINIC OVER THAT REGION AT
THAT TIME RANGE, SO DID NOT WANT TO JUMP ONTO SUCH AN ANOMALY AT
THIS STAGE, SETTLING ON AN INVERTED SURFACE TROUGH AS A MARKER FOR
THE FEATURE.

MOST OF THE PRECIPITATION THIS PERIOD WILL FOCUS OVER THE CENTRAL
STATES, WHERE GULF INFLOW WILL FEED CONVECTION ASSOCIATED WITH THE
PASSAGE OF MID-LATITUDE SHORTWAVES. SOUTHEASTERN FLORIDA WILL
LIKELY BE WET WITH THE APPROACH OF THE DISTURBANCE NEAR THE
BAHAMAS.


CISCO

[northjaxpro]

Actually, that scenario would be good and bad news. If the system develops and stalls out about a couple of hundred miles offshore, it would be far enough to not affect us, but we would be on the hot and dry subsident side of the system as well. It all depends on how close it gets to the Florida East Coast if this system comes to fruition next week.

[Hypercane_Kyle]

This would be interesting to see happen. The scenario slightly reminds me of TS Beryl in May 2012.

[crownweather]

Similar to Alberto in 2012 IIRC. Stayed far enough offshore to produce subsidence and gusty winds which enhanced the wildfire hazard in NE Florida.

[Hypercane_Kyle]

00z GFS is coming in a little closer to the US, holding strong with the idea of some sort of low developing.

[chaser1]

Well, global models couldn't be in much better agreement regarding the formation of what would easily appear to be a depression, and more likely a storm even given the apparent gradient between the forecast 1001 Low and higher pressures to the North. Having said that though, I must be wonky from a lack of recent sleep lately because, for the life of me..... I'm just not seeing how the models develop a T.S. providing 50 knot West to SW 200mb winds blowing over the system. I'm not privy to the EURO upper level charts, but am looking at the same one's that the GFS produces every 6 hour run. I really am confused how the GFS itself develops as deep a low as it does, provided the upper level shear its own dynamic modeling is projecting (and is presently in place) would seem quite unfavorable. Insights welcome....

[tolakram]

Good grief it's a bit early for this. If this isn't consensus I don't know what is.

ECMWF


GFS


CMC


NAVGEM


Source: http://moe.met.fsu.edu/tcgengifs/

[NDG]

Yes, very good concensus among ALL models of a subtropical type system developing next week near the Bahamas then move northward.
The Euro as always might be a bit west bias as usual, we will see.
BTW, SSTs are warm enough in that area for at least subtropical development.

[Hypercane_Kyle]

:double: Well, global models couldn't be in much better agreement regarding the formation of what would easily appear to be a depression, and more likely a storm even given the apparent gradient between the forecast 1001 Low and higher pressures to the North. Having said that though, I must be wonky from a lack of recent sleep lately because, for the life of me..... I'm just not seeing how the models develop a T.S. providing 50 knot West to SW 200mb winds blowing over the system. I'm not privy to the EURO upper level charts, but am looking at the same one's that the GFS produces every 6 hour run. I really am confused how the GFS itself develops as deep a low as it does, provided the upper level shear its own dynamic modeling is projecting (and is presently in place) would seem quite unfavorable. Insights welcome....

The non-tropical development in nature of this storm, high shear environment, plus how spread out the pressure gradient is, all suggests a sub-tropical cyclone to me IMO.

[Riptide]

Early glance at the 12z GFS looks to cave to the Euro or at least come ashore somewhere. 570 500mb thickness hugging the LP, looks warm core.

[Evil Jeremy]

As if the last of my finals this weekend weren't enough.
As if NFL fan in me going crazy about the draft this weekend wasn't enough.
As if the cinephile and economist in me analyzing Age of Ultron's record setting box office this weekend wasn't enough.

Now life decides to trigger another one of my obsessions. Seriously? A subtropical system now of all times?

grumble grumble grumble *opens dormant tropical tracking bookmarks*

[OuterBanker]

Jeremy and all. This is now a separate thread.

[euro6208]

GFS no longer providing surface pressure runs???

Contacted Levi and this is what he has to say. Too bad typhoon season is year round...

Hello,

I've had to remove it until further notice because it has been detecting pressure centers incorrectly for the WPAC domain only. I don't yet know why this is the case. All other regions work properly. I will be looking into it as typhoon season approaches.

Levi

Excellent news!

Full resolution is now back and just in time as it's modeling a very powerful typhoon...

Hello,

I just wanted to let you know that I have resolved the problem with the GFS surface pressure maps for WPAC. The plots are now back for that region.

Levi

[gatorcane]

wet-phase of MJO looks like it could be moving into the Western Caribbean starting in the next 10-14 days, though the wettest area is centered in the EPAC. GFS has started showing something forming in the Western Caribbean during this timeframe for the past several runs in a row.

Is this the usual GFS pre-season long-range Western Caribbean phantom storm it is showing or could there be something real here to keep an eye on (it correctly got Ana nearly two weeks out)?

[CFLHurricane]

Now this storm would truly be interesting if it pans out! Although I have my doubts with all that shear.

[NDG]

GFS does this every year, the storms end up developing on the EPAC side of C.A.

[TheStormExpert]

GFS does this every year, the storms end up developing on the EPAC side of C.A.

Haven't been checking the GFS the past few days, but according to local mets. it has been developing a system and bringing it near FL during the last week of May.

I HIGHLY DOUBT this will materialize and bet it's just the GFS being it's usual self every pre-season and blowing up phantom storms every run in the W. Caribbean just like last year.

[Florida1118]

GFS does this every year, the storms end up developing on the EPAC side of C.A.

Haven't been checking the GFS the past few days, but according to local mets. it has been developing a system and bringing it near FL during the last week of May.

I HIGHLY DOUBT this will materialize and bet it's just the GFS being it's usual self every pre-season and blowing up phantom storms every run in the W. Caribbean just like last year.

GFS does this every year, the storms end up developing on the EPAC side of C.A.

I just looked at the GFS, and didn't see anything of the sort. There is some activity towards the end of the run in the EPAC though.

[cycloneye]

Eric Blake ‏@EricBlake12 · 13m13 minutes ago
GFS keeping showing low pressure in the SW Carib in about a week-- seems like typical GFS WHemi convective bias

[Florida1118]

Looks like the EPAC is going to be ready to roll pretty soon:



Then around end of the month it really starts to get organized as it moves off the screen:



...and then for giggles, we get the expected tradition of a ghost storm floating around the basin in the fairytale hours: