648. Tropical Storm Norbert

TROPICAL STORM 19E (NORBERT)
PUBLIC ADVISORY #1
FORCE THIRTEEN SINGAPORE, SINGAPORE
1030 UTC WED OCT 7 2020

...NORBERT INGESTING DRY AIR...

SUMMARY OF 0900 UTC...INFORMATION
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LOCATION...NEAR 14.0 N 107.1 W...
MAXIMUM SUSTAINED WINDS...40MPH...60KM/H
MINIMUM CENTRAL PRESSURE...1005MB

WATCHES AND WARNINGS
-----------------------------------
NO WARNINGS IN EFFECT.

DISCUSSION
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 Norbert has weakened as entrainment of dry air has disrupted the 
compact system. The center was partially exposed overnight, but 
recent infrared imagery shows a new burst of deep convection near 
the center. Microwave imagery and ASCAT scatterometer wind data 
indicated the center had drifted southwest from its previous 
position, as the storm is beginning to meander within the weak 
steering flow. The initial intensity has been lowered to 35 kt based 
on the recent ASCAT-A overpass that showed a peak wind of 33 kt, as 
well as a T2.5 Dvorak estimate from TAFB. 

The intensity forecast for Norbert remains tricky given its small 
circulation and the presence of dry air in the surrounding 
environment. Sea-surface temperatures are more than sufficient for 
at least modest strengthening, but the question will be whether 
Norbert can survive the increased southeasterly shear that the 
SHIPS guidance calls for during the next 24-48 h. If so, Norbert 
may remain a tropical storm through the next 5 days. Alternatively, 
the shear and additional bouts of dry air entrainment could weaken 
the system to a depression or even a remnant low late in the 
forecast period. While small intensity changes due to diurnal 
fluctuations in convection are certainly possible, the official NHC 
forecast keeps Norbert's intensity forecast at 35 kt in 
consideration of the mixed signals noted in the latest intensity 
guidance.

LOCAL AND OFFICIAL SOURCES BELOW
National Hurricane Center (East Pacific)

NEXT FULL ADVISORY AT OCTOBER 7 2020, 1500 UTC.

$$
Forecaster Knack