MAJOR HURRICANE LARRY / INVEST 91L FORECAST SYNOPSIS…ISSUED SEP. 04, 2021…8:20 P.M. EDT

MAJOR HURRICANE LARRY / INVEST 91L FORECAST SYNOPSIS…ISSUED SEP. 04, 2021…8:20 P.M. EDT


Disclaimer:  This site is not affiliated with the National Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National Weather Service.  ALL forecasts herein are the result of my analysis, and I am solely responsible for the content.  As ALWAYS, follow the National Hurricane Center, National Weather Service, and your local Emergency Management officials for emergency decisions.  In addition, this is strictly a FORECAST OFFICE.  I CANNOT make decisions regarding travel plans, etc.  My purpose, is to provide you the information, based solely on information I analyze, and the accuracy of the information at hand of the time of analysis, so you may make informed decisions.
(T. F. “Storm” Walsh)

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Please be aware, even though I do not post every night, rest assured I am continuously monitoring various areas for any significant weather.  I will be taking Sundays off (family time), unless we have active systems that may be posing a threat (i.e. Tropical, Winter Weather, Coastal Storms, etc.).
STORM WALSH PRE-SEASON FORECAST
TOTAL NAMED STORMS: 17 – 20
TOTAL HURRICANES :        7 – 9
MAJOR HURRICANES:       4 – 5

AVERAGE HURRICANE SEASON:
TOTAL NAMED STORMS: 14
TOTAL HURRICANES:         7
MAJOR HURRICANES:       3

2021 SEASON TOTALS:
TOTAL NAMED STORMS:  12
TOTAL HURRICANES:          5
MAJOR HURRICANES:        3

TOTAL U. S. LANDFALLS:    6

The following is the list of storm names for the 2021 Atlantic Hurricane Season:
Ana Bill Claudette Danny Elsa Fred Grace Henri Ida Julian Kate Larry
Mindy Nicholas Odette Peter Rose Sam Teresa Victor Wanda
As a storm becomes named, I will be marking it in bold red to keep track of the activity for this Atlantic season.

Please note..when we are dealing with multiple systems, they will be listed in order as to the greatest threat to land or the U. S. , to the least threat.

Good evening everyone,
The following are satellite animations of the Tropical Atlantic and Africa
ATLANTIC ANIMATION
87057250ATL
In the following still, I have marked tropical waves over Africa
us_sat-en-087-0_2021_09_04_21_45_641_126
AFRICA ANIMATION
sat_20210904_2145_animation
Hurricane LARRY is now a MAJOR hurricane with sustained winds of 125 mph.  This makes LARRY a Category 3 hurricane on the Saffir-Simpson scale, and the THIRD major hurricane of the season.  As of the 5:00 p.m. EDT advisory, the following was available on LARRY:
5:00 PM AST Sat Sep 4
Location: 17.4°N 47.1°W
Moving: WNW at 14 mph
Min pressure: 958 mb / 28.29 in
Max sustained: 125 mph

Analysis of satellite loop imagery this evening shows LARRY is not as impressive as yesterday. with banding restricted to the north side of the storm.  This is most likley due to the fact thee has been some earlier onset of SWLY wind shear as noted in the CIMSS wind shear product.  Also noted, is the upper level outflow is restricted on the SW quadrant of the hurricane, most likley due to a TUTT NW of the hurricane, imparting the current shear.  In analysis last night, if you remember, the ECMWF indicated the onset of increasing shear, while the GFS indicated a more favorable upper pattern.  The current shear conditions were predicted by the ECMWF, earlier than what was shown by the GFS and the GFS SHIPS forecast product.  Based on my analysis this evening of forecast wind shear products, 200 mb streamline and speed forecast products,  and SST’s, wind shear is forecast to increase over the next 36 – 48 hours, which was indicated in the ECMWF shear forecast.  However, from 60 hours on, the pattern becomes fairly favorable once again, as the TUTT to the NW of LARRY pretty much dissipates (based on the current ECMWF 200 mb forecast).  By 72 hours in the period, LARRY could increase in strength slightly, prior to beginning his final weakening stage.  Analysis of the forecast 500 mb relative humidity values do indciate LARRY will be ingesting slightly, some dry air.  However, I do not believe at this particular time that it will affect the intensity of the storm, as the dry air doesn’t appear to reach the core of the hurricane.  NOW, I usually don’t do this, however I have to give a hearty KUDOS to the forecaster at the NHC who did the current forecast discussion.  What I just posted above, is based on my analysis, and is MY own forecast, in which I perform prior to looking at NHC information.  I must say, I am very impressed by this forecaster from the NHC, as he NAILED the synopsis right on the money, and in my opinion, is what should occur.  Again, KUDOS to forecaster Papin from the NHC.  The following is from the NHC 5:00 P.M. discussion:

The existence of some light upper-level southwesterly flow ahead of 
Larry today was bit of a surprise, since the SHIPS guidance from the 
last few days suggested the shear-vector would be out of the east 
and weak. Indeed, the latest ECMWF-SHIPS guidance now shows moderate 
southwesterly vertical wind shear beginning earlier, and peaking 
between 20-25 knots in 36 to 48 hours. While the GFS-SHIPS shear 
remains much lower, given what I'm seeing from the latest 
upper-level flow in front of Larry, the ECMWF seems closer to 
correct. For this reason, the latest NHC intensity guidance now 
shows a bit of weakening after 24 hours, when the shear magnitude is 
expected to peak as the hurricane interacts with a large tropical 
upper-tropospheric trough (TUTT) located to its northwest. However, 
Larry has a large and vertically-deep circulation, and ultimately it 
will win the battle against the more vertically shallow TUTT, which 
is forecast to cut off and move away from the hurricane's expansive 
upper-level outflow. By 60 hours, this change in the synoptic 
pattern should once again reduce the vertical wind shear over Larry, 
and it will have a chance to achieve a secondary peak between the 
60-84 hour time-frame.

CIMSS WIND SHEAR AND UPPER LEVEL WINDSLARRY.SHEAR
LARRY.UPPER
ECMWF WIND SHEAR AND UPPER LEVEL WIND FORECAST
ecmwf-deterministic-catl-shear_850v200-0843200
ecmwf-deterministic-catl-shear_850v200-0929600
ecmwf-deterministic-catl-shear_850v200-1016000
ecmwf-deterministic-catl-z200_speed-1016000
ECMWF 500 MB RH FORECAST
ecmwf-deterministic-catl-rh500-1630756800-1630756800-1631188800-40
Based on my analysis of these forecast conditions, I concur with the NHC intensity forecast at the moment.
NHC INTENSITY FORECAST
INIT 04/2100Z 17.4N 47.1W 110 KT 125 MPH

12H 05/0600Z 18.4N 48.6W 115 KT 130 MPH
24H 05/1800Z 19.8N 50.6W 120 KT 140 MPH
36H 06/0600Z 21.0N 52.3W 115 KT 130 MPH
48H 06/1800Z 22.2N 54.0W 110 KT 125 MPH
60H 07/0600Z 23.4N 55.6W 110 KT 125 MPH
72H 07/1800Z 24.7N 57.0W 115 KT 130 MPH
96H 08/1800Z 28.3N 59.9W 110 KT 125 MPH
120H 09/1800Z 33.4N 61.9W 95 KT 110 MPH

LARRY was moving toward the WNW or 300 Degrees.  Analysis of current and forecast steering layers maps suggest LARRY should maintain this motion up until late Monday or early Tuesday, before a more NW or NNW track begins.  Based on forecast steering, and projected motion of the ECMWF and GFS global models, the center of LARRY should pass east of Bermuda.  Based on this analysis, and the current track guidance, I agree with the NHC forecast track.
LARRY 18Z ATCF GUIDANCE
aal12_2021090418_track_early
ECMWF EPS AND GEFS GUIDANCE
AL12_2021090412_ECENS_large
AL12_2021090412_GEFS_large
NHC TRACK MAP
205749_5day_cone_no_line_and_wind
Elsewhere, I am still monitoring INVEST 91L, over the Yucatan Peninsula.  91L should be emerging into the BOC (Bay Of Campeche) by tomorrow.  As of analysis this evening of forecast steering over the GOMEX during the next 72 – 96 hours, the “projected motion” of the NHC yellow, hatched area looks fairly good.  However, future motion of this feature will depend on any development that may occur, and how strong 91L becomes, if it develops at all.  Between the ECMWF, GFS, and CMC global models, the GFS and CMC are the only ones indicating a “weak” development, with the ECMWF just indicating an area of lowering MSLP anomalies.  The NHC has designated a LOW (30%) probability for cyclone development during the next 5 days.
NHC 5 DAY GTWO
two_atl_5d1
Based on my analysis of the wind shear forecast from both the ECMWF and GFS, upper level winds are forecast to remain marginal to unfavorable for the next 72 hours.  Shortly thereafter, both models indicate the upper level conditions may improve enough to where slow development could begin.  Current forecast RH values indicate mid level moisture should be within a favorable range.  Currently, with the GFS and CMC indicating a weak system, we “could” see a Tropical Depression develop closer to the 5 day period.  Confidence in the forecast on 91L should be considered low, until I can see where the “center” emerges over water, and if it begins to consolidate. Satellite imagery from earlier this evening may indciate a “center” trying to develop north of where the current center is marked.
INVEST 91L VISIBLE LOOP
10289134
ECMWF WIND SHEAR AND UPPER LEVEL WINDS FORECAST
ecmwf-deterministic-gulf-shear_850v200-1016000
ecmwf-deterministic-gulf-shear_850v200-1091600
ecmwf-deterministic-gulf-z200_speed-1091600
GFS, CMC, AND ECMWF MSLP NORMALIZED ANOMALIES FORECAST
gfs-deterministic-gulf-mslp_norm_anom-1124000
gem-all-gulf-mslp_norm_anom-1145600
ecmwf-deterministic-gulf-mslp_norm_anom-1091600
I will continue to monitor INVEST 91L for any significant changes to the forecast parameters during the next 48 hours.

You may direct any questions by contacting me personally, ANYTIME, at: [email protected]

Have a blessed evening!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS

 

 

About palmharborforecastcenter

I am a Tropical Forecast meteorologist, providing hurricane forecasts during the Atlantic Hurricane Season. I retired from the U.S. Coast Guard in July of 2001. Meteorology became my passion in high school, and I have continued my educational background in meteorology since 1996, when I undertook the study of Tropical Meteorology. While working toward my degree, I had to unexpectedly withdraw from college due to my oldest sons medical reasons. I do however, meet the educational criteria of the AMS to be recognized as a meteorologist. Studies include, but are not limited to the Navy Aerographers Mate course, Naval METOC meteorology course, Meteorology 2010 Sophomore level course while attending St. Petersburg College, Clearwater, FL., Basic Forecasting course for operational meteorologists from Rapid WX, meteorology institute, a four month meteorological internship, and extensive research on numerous meteorological topics such as the MJO, NAO, satellite imagery interpretation, etc.

I have been forecasting Tropical Weather (Tropical Storms and Hurricanes) since 1996, with my main client being three different Coast Guard Commands.



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