August 2017: Looking Back at Harvey 5 Year Later

[stormlover]

climatology!!

[srainhoutx]

Friday morning briefing from Jeff:

Tropical Storm Harvey

Tropical Storm Warnings are in effect for the Windward Islands

Discussion:
The area of low pressure approaching the Windward Island yesterday was upgraded to Tropical Storm Harvey based on the afternoon USAF mission yesterday. Overnight the convective cloud pattern of Harvey has shown little organization with sporadic bursts of convection and very little if any banding features. Mid and upper level easterly shear continues to hamper the circulation removing what thunderstorms that do develop toward the W/SW side of the system. Early this morning the “center” passed very near Barbados with a minimum surface pressure of 1006mb reported at the airport. Since then the morning USAF mission has had a hard time finding a defined low level center with the first pass showing only hints of westerly winds on the south side of where the center was expected to be. The plane has found an area of near tropical storm force winds across the northern semi-circle of the circulation. It may be that the small and well defined center yesterday has become more broad and disorganized overnight.

Track:
Harvey is embedded with a fast east to west steering flow on the south side of a strong sub-tropical high pressure ridge over the central Atlantic Ocean. This will force Harvey on an almost due west motion of the next 2-3 days and model track guidance is in “very” good agreement on the track reasoning through day 3 (Sunday). There is very little spread in the dynamical guidance nor the 12/24 time points through 72 hours which is leading to above average forecast track confidence through day 3.

On this track Harvey will move across the eastern and central Caribbean Sea and approach the northern coast of Honduras late this weekend. By days 4/5 (early next week) Harvey will likely be located over the western Caribbean Sea approaching either Belize or the Yucatan. It is possible that Harvey could landfall along the northern coast of Honduras or track just north over the open waters of the SW Caribbean Sea.

Longer range dynamical guidance begin to rapidly showing significant spread developing as Harvey crosses the Yucatan and enters the southern Gulf of Mexico. Much of this spread hinges around the upper level tropical trough (TUTT) currently over Cuba and the Bahamas which will move westward and arrive into the NW Gulf of Mexico around Monday. This TUTT low begins to weaken, fill, and shear out by the middle of next week, but the ECMWF and CMC leave a weakness or break in the sub-tropical ridge over TX which in turn allows Harvey to turn NW or NNW in the Gulf of Mexico. The GFS rapidly fills the weakness over TX by a building sub-tropical ridge and keeps Harvey buried deep in the southern Gulf of Mexico. It should be noted that the GFS and ECMWF are hundreds of miles apart by days 6-7 over the Gulf of Mexico with the CMC in the middle of the two outlier solutions. Additionally, given the weakening of the sub-tropical ridge to the northern of Harvey a decrease in forward speed is likely by the early to middle part of next week and both the CMC and ECMWF show Harvey potentially stalling or meandering over the Gulf of Mexico. Hence confidence in the forecast track while very high through day 3 is low after day 5.

Intensity:
USAF mission data this morning and satellite images show a poorly defined tropical storm that is fighting easterly wind shear. Harvey is a small tropical system which makes it vulnerable to changes in environmental changes surrounding the system which can result in rapid changes in intensity. There is likely some question as to if Harvey even has a closed center anymore, but for now until the plane can provide more passes it shall be kept as a tropical storm. Looking at the live recon data it appears the center may have reformed WSW overnight around 12.5N or there could be smaller scale circulations rotating around a mean larger circulation…point being Harvey is not well organized.

Neither the GFS nor the ECMWF have shown much support for Harvey through the next 48-72 hours and have even suggested the system will degenerate into an open wave axis before organizing again in the western Caribbean Sea. Historically tropical systems that are not well developed prior to entering the eastern Caribbean Sea struggle due to the divergence of the low level trade wind flow in this region. The more statistical guidance shows Harvey slowly intensifying as it moves westward and the current NHC forecast is following a compromise between the weaker and much aggressive intensity guidance camps. Conditions do appear more favorable once in the western Caribbean Sea, and if Harvey can limp along and come under those better conditions more sustained intensification would be possible. The latest NHC forecast brings Harvey to a 70mph TS before landfall over Belize/Yucatan.

92L:
A tropical wave located roughly 750 miles ENE of the northern Leeward Islands is showing some modest signs of organization. Deep convection has developed over/near a center overnight, but the recent past few days have shown sporadic attempts at organization. This wave is closer to dry air surrounding it to the north which is likely ingesting into the circulation at times cutting down on sustained convective formation. It would only take a small increase in organization to bring this to TD status and that may be possible before an upper level low NNE of the system begins to result in increasing shear over the next 48 hours. 92L may find much more favorable conditions as it nears the Bahamas early next week where more significant development would be possible.

[/i]

[brooksgarner]

NICE TO HAVE THE FORUM BACK, AFTER THAT HICCUP YESTERDAY. I'm pleased to see the database remained intact.

Yikes... 00z EURO run... for weather on August 28th.

ecmwf_uv10g_tx_41.png

Of course, everyone reading this knows -- or now knows -- that 10 day computer model forecasts are almost meaningless when it comes to placement and strength of tropical systems this far out. It would be just plain 'ol dumb luck if what eventually happens is even close to this 2-week projection, considering the always unresolvable chaos-theory endemic in long-range computer modelling. It's Armageddon nonetheless. What these can help with is to demonstrate overall atmospheric conditions for that period: will weather conditions in the Gulf be conducive for hurricanes during that time period when an already-existent tropical system approaches? Will they be highly un-conducive? Will steering currents tend to pull systems north, or suppress them south? At least this type of outlook can suggest we're looking at favorable conditions thru late-month. The peak of the season is Sept 10th, so it's obviously a potential.

European Ensemble guidance continues to demonstrate two main possible tracks, one of which is not good for our interests in Texas.

DHhFDedXsAAlMZx.jpg

But, it's that time of year again... quietly prepare just in case the system rides the northern edge of the cone ...

145613_5day_cone_no_line_and_wind.png

So, we won't write Harvey off just yet... Then there's 92L...

[tireman4]

Thanks for all you do Brooks. We appreciate you ( and all the other pro mets, Jeff, Andrew, Srain, Wxman 57 and others I forgot to mention) for coming on and giving your updates. Stay vigilant as Dr. Neil Frank likes to say.

[brooksgarner]

Thanks for all you do Brooks. We appreciate you ( and all the other pro mets, Jeff, Andrew, Srain, Wxman 57 and others I forgot to mention) for coming on and giving your updates. Stay vigilant as Dr. Neil Frank likes to say.

It's my pleasure! Doc is right... don't forget those non-descript, degenerate tropical systems because they can act differently in their track than a full-developed system, which can trick many short/medium range computer models into suggesting it'll go one way, when it's really going another way.

[srainhoutx]

Good full package Discussion from Jack Beven...

Tropical Storm Harvey Discussion Number 5
NWS National Hurricane Center Miami FL AL092017
1100 AM AST Fri Aug 18 2017

The structure of Harvey has changed little during the past several
hours, and overall the storm is poorly organized. The low-level
center is near the eastern edge of the convective mass due
to the affects of 15 kt of vertical wind shear. In addition,
surface observations and Air Force Reserve Hurricane Hunter data
suggest that the 850-mb center is located west or southwest of the
surface center. Based on the aircraft and surface data, the central
pressure is near 1005 mb and the initial intensity remains 35 kt.

The initial motion is a quick 270/18. A strong low- to mid-level
ridge north of the cyclone should keep Harvey on this general motion
for the next 3-4 days, with the system moving from the eastern to
the western Caribbean Sea during this time. Late in the forecast
period, a more northerly motion is expected when Harvey passes near
or over portions of Central America, the Yucatan Peninsula, and
eastern Mexico. The new forecast track remains in the center of the
guidance, and only minor changes were made to the previous track.

The current shear should persist for the next 48 h or so, and thus
the intensity forecast continues the trend of slow strengthening
during this time. After that, conditions appear favorable for
strengthening, with the main uncertainty being how much land Harvey
will encounter. The ECMWF keeps the cyclone a little north of
Nicaragua and Honduras and allows more room for development, while
the GFS forecasts landfall in northeastern Nicaragua and thus has a
weaker intensity. The new NHC forecast is close to the previous
one in showing a peak intensity below hurricane strength, but
the confidence in this portion of the forecast is low.

FORECAST POSITIONS AND MAX WINDS

INIT 18/1500Z 13.1N 61.3W 35 KT 40 MPH
12H 19/0000Z 13.3N 63.8W 35 KT 40 MPH
24H 19/1200Z 13.6N 67.3W 40 KT 45 MPH
36H 20/0000Z 14.0N 71.1W 40 KT 45 MPH
48H 20/1200Z 14.3N 75.0W 50 KT 60 MPH
72H 21/1200Z 15.0N 82.0W 60 KT 70 MPH
96H 22/1200Z 16.5N 87.5W 55 KT 65 MPH
120H 23/1200Z 18.5N 91.0W 30 KT 35 MPH...INLAND

$$
Forecaster Beven

[tireman4]

I hope he wont mind, but on another forum, Wxman 57 gave his thoughts..If he does, he can yell at me later...LOL..

"
I don't trust the GFS with its upper air pattern beyond 3-4 days. The ECMWF is very inconsistent from run to run, which isn't giving me much confidence either. The UKMET, which often does well with TCs, buries Harvey in southern Mexico. I'm still forecasting an emergence into the BoC next Wednesday afternoon (or so) then westward into Mexico (south of Tampico). However, I wouldn't declare the NW Gulf "safe" by any means. Long-range ensemble guidance indicates a 10% chance of a south Texas impact (from tropical storm-force winds, not necessarily the center). If I were you, I'd give my hurricane kit another look and make sure everything is there and ready to go - just in case.

That goes for any of you from Texas to Louisiana. You should have your kit ready to go at the beginning of the season, but now would be a good time to make sure it's OK.

I'll feel more confident as to the final landfall once the models are in much better agreement. Hopefully by Monday. Maybe earlier."

[stormlover]

https://www.tropicaltidbits.com/analysi ... 0&ypos=170

navy model

[DoctorMu]

https://www.tropicaltidbits.com/analysi ... 0&ypos=170

navy model

Just noticed that. It's gone on the 12Z Euro. Just keep our eyes peeled. I'd take a tropical wave - we're getting parched again.

[Ounce]

Thanks for all you do Brooks. We appreciate you ( and all the other pro mets, Jeff, Andrew, Srain, Wxman 57 and others I forgot to mention) for coming on and giving your updates. Stay vigilant as Dr. Neil Frank likes to say.

It's my pleasure! Doc is right... don't forget those non-descript, degenerate tropical systems because they can act differently in their track than a full-developed system, which can trick many short/medium range computer models into suggesting it'll go one way, when it's really going another way.

Yes, thanks, Brooks. Does the station reimburse you in Bitcoin for paying the ransom on this forum?

[Scott747]

There shouldn't be much surprise with the windshield flop by the Euro. It's been showing some very wide solutions. 12z was about less of a weakness and a bit faster. No chance to pull n....

Track will likely shift s at 4. 0z runs are getting into range where we might get a better idea on any weakness developing like the 0z Euro run showed.

[tireman4]

There shouldn't be much surprise with the windshield flop by the Euro. It's been showing some very wide solutions. 12z was about less of a weakness and a bit faster. No chance to pull n....

Track will likely shift s at 4. 0z runs are getting into range where we might get a better idea on any weakness developing like the 0z Euro run showed.

Road trip Scott?

[brooksgarner]

Thanks for all you do Brooks. We appreciate you ( and all the other pro mets, Jeff, Andrew, Srain, Wxman 57 and others I forgot to mention) for coming on and giving your updates. Stay vigilant as Dr. Neil Frank likes to say.

It's my pleasure! Doc is right... don't forget those non-descript, degenerate tropical systems because they can act differently in their track than a full-developed system, which can trick many short/medium range computer models into suggesting it'll go one way, when it's really going another way.

Yes, thanks, Brooks. Does the station reimburse you in Bitcoin for paying the ransom on this forum?

LOL! If only... what is it up to these days, $4,000 per bitcoin? Than, yes! Hey, I'm here with y'all and for you. Cheers!

[Scott747]

18z gfs wants to add a little suspense. Not quite like last nights Euro run, but 'hints' at it.

[srainhoutx]

I suspect we will see plenty of assets thrown at Harvey next week. Clearly the guidance is struggling with the various upper air features expected next week. My hunch is we will see Global Hawk and possibly G-IV missions tasked.

[Belmer]

As we know, models have not been excellent with Harvey as far as consistency. Anywhere from Nicaragua to SETX have been the spread the past couple of days. My two cents is that the models are just not handling the hostility going on in the Atlantic as it is quite active with Harvey, 92L, the wave behind that, as well as two large ULL and high pressure in the central Atlantic. Lot of dynamics at play and modeling isn't handling the upper air environment very well. As we've seen the past 24 hours, don't get caught up on one model run (calling you out 00z ECMWF).

With that said, it is interesting to note that the models do seem to be picking up the weakness on a trough coming down and trying to steer it northward. As seen in the images below, most models are starting to shift further north. Especially in the last 24 hours. Tomorrow could definitely be a different story and shift back south and bury Harvey into Central America/Mexico. Statistically speaking, it is rare for a storm to enter into the far southern part of BoC and head NNW or due North, but it has happen. If Harvey can slow down a bit, and the ULL over the Gulf weakens as it heads west towards TX, and the trough can dig down far enough, the weakness could very well be enough to put at least southern TX into play.

As far as the 10PM advisory from NHC on Harvey, didn't move the cone too far North, as I wouldn't expect them to in this model war inconsistency, but if the overnight models continue the trajectory of a slow northern turn once it crosses the Yucatan, I would suspect the NHC to follow suit by the 11AM advisory.


Side note - I haven't posted on here for a while, and I see some new users on this board, so wanted to say 'WELCOME'. I was very active on this board pre-college days. But meteorology took over my life and now the adult world has done the same, so I haven't had a chance to be as active as I would like to be. Though I am so happy to see this board alive and well. Many thanks to Steve for his contribution and knowledge as well as wxman57 along with many other senior members. It is always nice to have this forum for us weather nerds (and those who like to use this to get general weather information).

Blake.

[Scott747]

There shouldn't be much surprise with the windshield flop by the Euro. It's been showing some very wide solutions. 12z was about less of a weakness and a bit faster. No chance to pull n....

Track will likely shift s at 4. 0z runs are getting into range where we might get a better idea on any weakness developing like the 0z Euro run showed.

Road trip Scott?

Depends. Consensus on a Tampico hit or s, and limited chance with a miss towards Brownsville, and Josh flies into Mexico City and I'm out. Change it around and chance that's there a miss more towards Brownsville and I'm in play. Just going off where we're at with the current possibilities even through at this place in time the track is still very much up in the air.

[Scott747]

0z gfs is further n. S of Brownsville.

Trend is only there if the Euro shows something similar. Mentioned earlier that we might see with the 0z runs the beginning of an idea on how real the possibility of a weakness upstream would have on Harvey.

[Belmer]

Overnight model runs continue the northern trend, though, the 06z models are a bit more clustered over northern Mexico and southern TX compared to the 00z run.

00z Euro has Harvey heading toward Tampico, MX... unlike last night where it was sniffing at the upper TX coast.

[srainhoutx]

There are still a lot of challenges ahead in the forecast beyond 5 days, so expect changes in the week ahead regarding Harvey and what our sensible weather will actually be. Eric Blake provided and excellent synoptic analysis with the 4:00 AM Full Package Discussion regarding what is currently expected for Harvey over the next 5 days...

Tropical Storm Harvey Discussion Number 8
NWS National Hurricane Center Miami FL AL092017
500 AM AST Sat Aug 19 2017

GOES-16 shortwave infrared imagery shows the partially exposed
center of Harvey on the eastern edge of a large area of deep
convection. While the center is closer to the convection than a few
hours ago, cirrus clouds be clearly seen moving from northeast to
southwest across the system; an indication of the persistent shear.
Satellite estimates suggest the maximum winds of Harvey remain 35
kt.

The storm has picked up some forward speed with a recent motion
estimate of 275/18. A low- to mid-level ridge extending across the
western Atlantic should keep Harvey on a fast westward course across
the Caribbean Sea for the next 48 hours. Thereafter, the ridge
weakens across the Gulf of Mexico due to a strong mid/upper-level
low currently seen there on water vapor images. This steering flow
change should cause Harvey to slow down and turn a little more to
the west-northwest in the northwestern Caribbean Sea, with an even
slower motion forecast for Harvey in the Bay of Campeche. Model
guidance is in fairly good agreement on this scenario, and no
significant changes were made to the previous forecast.

Harvey should be moving into a more conducive environment for
strengthening early next week since the strong northeasterly shear
that has been affecting the cyclone is forecast by almost all of the
guidance to weaken within about 24 hours. In a few days, most of
the global models show a favorable upper-level environment for
intensification, and Harvey could be near hurricane strength between
the 72 hour forecast period and landfall. There has been little
change to the guidance so the new intensity forecast is similar to
the previous one, close to the model consensus. However, with
a weak storm moving so quickly across the central Caribbean, one
always has to be careful of the system opening up into a wave. This
is a plausible alternative scenario still suggested by the GFS and
ECMWF models.


FORECAST POSITIONS AND MAX WINDS

INIT 19/0900Z 13.8N 65.9W 35 KT 40 MPH
12H 19/1800Z 14.0N 68.7W 35 KT 40 MPH
24H 20/0600Z 14.3N 72.7W 40 KT 45 MPH
36H 20/1800Z 14.6N 76.7W 45 KT 50 MPH
48H 21/0600Z 15.2N 80.1W 50 KT 60 MPH
72H 22/0600Z 17.0N 86.5W 55 KT 65 MPH
96H 23/0600Z 18.3N 90.5W 35 KT 40 MPH...INLAND
120H 24/0600Z 19.3N 93.0W 40 KT 45 MPH...OVER WATER

$$
Forecaster Blake


The main take away from Eric's analysis is shear is expected to drop dramatically over the next 24 hours since Harvey's forward motion to the West has increased overnight. Conditions appear to become extremely favorable over the NW Caribbean as Harvey slows way down before approaching the Yucatan Peninsula.

The attachment 084550_5day_cone_no_line_and_wind.png is no longer available

Early morning analysis suggests that TUTT will continue to meander West throughout the next 5 or so days before shearing out near S Texas.

The overnight ECMWF EPS suggests another deep trough over the Eastern United States and another in the Pacific NW. Heights are rather low across the Western and NW Gulf of Mexico later next week which raises an eyebrow. Also the overnight guidance has slowly coming to a consensus that a frontal boundary may stall across the Northern Gulf Coast. Generally it appears a weakness develops allowing Harvey to move very slowly as the mean steering flow collapses. While it is far to soon to know with any certainty exactly what the future eventual final track and intensity will be for Harvey, I as well as HGX Forecaster Overpeck suggest that everyone take this quiet time ahead to review your personal Hurricane Action Plan and replenish any supplies you and your family may need. Why wait any longer? We still have about 5 to 7 weeks ahead as we approach that Climatology Peak of Hurricane Season.

As our good friends and big supporters of our efforts here on the KHOU Weather Forum Dr. Neil Frank and Bill Read will tell you, the guidance beyond 5 Days is just noise to the Hurricane Specialist at the National Hurricane Center.