562
WTPZ45 KNHC 131459
TCDEP5
HURRICANE SIMON DISCUSSION NUMBER 25
NWS NATIONAL HURRICANE CENTER MIAMI FL EP202026
800 AM MST TUE OCT 13 2026
SMALL STUBBORN SIMON CONTINUES TO DEFY EXPECTATIONS THIS MORNING.
FIRST LIGHT VISIBLE SATELLITE IMAGERY SHOWS THE HURRICANE STILL HAS
A SMALL EYE, AND IS ALSO LOCATED FARTHER SOUTH THAN WAS ANALYZED BY
SATELLITE IMAGERY LAST NIGHT. THIS IS FURTHER SUPPORTED BY MICROWAVE
IMAGES FROM AMSR-3 AT 09 UTC AND SSMIS AT 1125 UTC WHICH BOTH SHOW
AN EYEWALL THAT IS LITTLE BETTER ORGANIZED, THOUGH IT REMAINS OPEN
ON THE WEST SIDE. THIS STRUCTURE COULD BE DUE TO SOME RESIDUAL SHEAR
OR DRY AIR THAT WAS INGESTED INTO THE CIRCULATION. SATELLITE
INTENSITY ESTIMATES ARE ALL OVER THE PLACE THIS MORNING, RANGING
FROM AS LOW AS 47 KT FROM UW-CIMSS ADT, AND AS HIGH AS 95 KT BY
SATCON. GIVEN THE SMALL EYE SIGNATURE SURROUNDED BY -65 TO -70 C
COLD CLOUD TOPS, THE INITIAL INTENSITY WILL BE HELD AT 80 KT, ON THE
UPPER SIDE OF THESE ESTIMATES, BUT SHOULD BE CONSIDERED MORE
UNCERTAIN THAN USUAL.
SIMON CONTINUES TO MOVE SOUTH OF THE PREVIOUS FORECAST TRACK, AND
THE INITIAL MOTION IS A SLOW WESTWARD DRIFT AT 270/2 KT. THE FARTHER
SOUTH INITIAL POSITION AND CURRENT MOTION NECESSITATES SOME PRETTY
SIGNIFICANT CHANGES TO THE SHORT-TERM TRACK FORECAST. AS MENTIONED
YESTERDAY, SIMON IS VERY CLOSE TO A SADDLE POINT, OR COL, IN THE
DEEP-LAYER STEERING FLOW. THIS FEATURE MEANS THAT SIMON'S FUTURE
TRACK IS VERY SENSITIVE TO WHICH SIDE OF THE SADDLE POINT THE STORM
IS LOCATED. YESTERDAY, A PLURALITY OF THE GUIDANCE WAS MAINTAINING
SIMON ON A NORTHWESTWARD TO NORTHWARD TRACK, CAUSING IT TO BE ON THE
NORTH SIDE OF THE SADDLE POINT, RESULTING IN CONTINUED POLEWARD
MOTION. HOWEVER, SIMON HAS GAINED VERY LITTLE LATITUDE OVER THE PAST
24 H, AND THUS NOW FINDS ITSELF ON THE SOUTH SIDE OF THE SADDLE
POINT. CONSEQUENTLY, THE TRACK GUIDANCE OVER THE PAST FEW CYCLES HAS
SHIFTED SUBSTANTIALLY SOUTHWARD. THE NHC TRACK FORECAST IS NOW
SHIFTED IN A SIMILAR FASHION, SHOWING A VERY SLOW MOTION OVER THE
NEXT 36-48 H AS SIMON MAKES A SMALL CYCLONIC LOOP. THE FIRST PART OF
THE TRACK FORECAST IS SUBSTANTIALLY FARTHER SOUTH THAN THE PRIOR
ONE, BUT STILL NOT AS FAR SOUTH AS THE HFIP CORRECTED CONSENSUS
APPROACH (HCCA), OR ANY OF THE LATEST HURRICANE-REGIONAL MODELS.
AFTER 48 H, DEEP-LAYER STEERING FINALLY BEGINS TO SHIFT OUT OF THE
SOUTH AS A DEEP-LAYER CUTOFF LOW DIGS INTO SOUTHERN CALIFORNIA, AND
SIMON WILL FINALLY START MOVING NORTHWARD IN EARNEST DURING THE
48-72 H TIME FRAME. TOWARDS THE END OF THE FORECAST, SIMON COULD
BEND BACK MORE NORTH-NORTHWESTWARD, POTENTIALLY ENTERING THE GULF OF
CALIFORNIA AND FINALLY MAKING LANDFALL IN MEXICO BETWEEN 96-120 H.
HOWEVER, THIS FORECAST SHOULD BE CONSIDERED VERY LOW CONFIDENCE AT
THAT TIME FRAME, AS THERE ARE A HOST OF SOLUTIONS FROM LANDFALL IN
MAINLAND MEXICO EVEN BEFORE REACHING THE GULF OF CALIFORNIA, DIRECT
IMPACTS TO BAJA CALIFORNIA SUR, OR SOLUTIONS THAT STAY SOUTH OF
MEXICO ENTIRELY OVER THE NEXT 5 DAYS.
THE INTENSITY FORECAST IS NOT MUCH EASIER EITHER. SIMON HAS MANAGED
TO MAINTAIN A SMALL INNER-CORE AND HURRICANES OF THIS SIZE ARE KNOWN
TO BE SENSITIVE TO SMALL CHANGES IN THEIR ENVIRONMENTAL CONDITIONS
THAT COULD RESULT IN RAPID CHANGES IN INTENSITY, EITHER UP OR DOWN.
THIS IS ALSO EXHIBITED IN THE INTENSITY GUIDANCE THIS MORNING, WHICH
RANGES FROM SIMON WEAKENING TO A TROPICAL DEPRESSION ALL THE WAY TO
IT REGAINING MAJOR HURRICANE INTENSITY OVER THE NEXT 48-60 H. WHILE
SHEAR OVER SIMON IS EXPECTED TO REMAIN LOW FOR THE NEXT 48 H AND
SEA-SURFACE TEMPERATURES (SSTS) ARE IN THE 29-30 C RANGE, ONE WILD
CARD IS HOW SIMON'S SLOW MOTION MIGHT CAUSE SOME COOL OCEAN
UPWELLING. THERE IS ONE OCEAN GLIDER PROVIDING SUBSURFACE OCEAN
TEMPERATURE DATA NEAR SIMON, AND IT DEPICTS 28 C WATERS DOWN TO
ABOUT 80 M BELOW THE OCEAN SURFACE. ASSUMING SIMON DOES NOT
COMPLETELY STALL, THIS IS LIKELY TO SUPPORT IT MAINTAINING HURRICANE
INTENSITY FOR THE NEXT 48-72 H. GIVEN ALL THIS INFORMATION, THE NHC
INTENSITY FORECAST WILL SHOW SIMON MAINTAINING ITS INTENSITY AS AN
80 KT HURRICANE FOR THE NEXT 48 H. AFTERWARDS, SOUTHWESTERLY
VERTICAL WIND SHEAR IS FORECAST TO INCREASE IN EARNEST, AND THE
SMALL SIMON IS FORECAST TO QUICKLY WEAKEN EVEN AS IT MOVES OVER
WARMER SSTS. THIS LATEST FORECAST IS INITIALLY ON THE HIGH SIDE OF
THE GUIDANCE ABOVE HCCA, BUT NOT AS HIGH AS THE LATEST HAFS-A,
COAMPS-TC, OR HMON RUNS. AFTER 48 H THIS FORECAST FALLS BACK TO THE
MIDDLE OF THE GUIDANCE ENVELOPE.
IT IS WORTH STRESSING THAT THIS IS A VERY LOW CONFIDENCE FORECAST
FOR BOTH TRACK AND INTENSITY, AND INTERESTS IN WEST-CENTRAL MEXICO
AND BAJA CALIFORNIA SUR SHOULD CONTINUE TO CLOSELY MONITOR THE
LATEST UPDATES. CHANGES TO WATCHES AND WARNINGS COULD BE REQUIRED
LATER TODAY BASED ON THE LATEST FORECAST TRENDS.
KEY MESSAGES:
1. SIMON COULD APPROACH LAS ISLAS MARIAS ON WEDNESDAY AND THE COAST
OF WESTERN MEXICO LATER THIS WEEK AT OR NEAR HURRICANE STRENGTH, AND
A HURRICANE WATCH IS IN EFFECT FOR A PORTION OF THESE AREAS.
INTERESTS IN WEST-CENTRAL MEXICO AND BAJA CALIFORNIA SUR SHOULD
CONTINUE TO CLOSELY MONITOR THE LATEST UPDATES TO SIMON'S FORECAST.
CHANGES TO WATCHES AND WARNINGS COULD BE REQUIRED LATER TODAY BASED
ON THE LATEST FORECAST TRENDS.
2. LARGE SWELLS WILL AFFECT PORTIONS OF THE SOUTHWESTERN AND
WEST-CENTRAL COASTS OF MEXICO OVER THE NEXT SEVERAL DAYS. THESE
SWELLS ARE LIKELY TO CAUSE LIFE-THREATENING SURF AND RIP CURRENT
CONDITIONS.
FORECAST POSITIONS AND MAX WINDS
INIT 13/1500Z 20.3N 107.3W 80 KT 90 MPH
12H 14/0000Z 20.3N 107.6W 80 KT 90 MPH
24H 14/1200Z 20.3N 107.8W 80 KT 90 MPH
36H 15/0000Z 20.1N 107.9W 80 KT 90 MPH
48H 15/1200Z 20.1N 107.7W 80 KT 90 MPH
60H 16/0000Z 21.0N 107.8W 75 KT 85 MPH
72H 16/1200Z 22.8N 108.2W 70 KT 80 MPH
96H 17/1200Z 25.2N 109.6W 55 KT 65 MPH
120H 18/1200Z 28.5N 110.5W 30 KT 35 MPH...POST-TROP/INLAND
FORECASTER PAPIN
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