Post-Tropical Cyclone Blanca Discussion Number 19
NWS National Hurricane Center Miami FL EP022021
200 AM PDT Fri Jun 04 2021
Blanca has been devoid of organized deep convection since midday
yesterday, with the last convective burst near the center ceasing
over 15 hours ago. Since that time there have been a few convective
cells noted 120 to 150 n mi east-northeast of the center, but these
have been short lived. This is a big change from this time
yesterday, when a large burst of deep convection developed during
the diurnal maximum close the center of the cyclone. This trend is
indicative of the strong west-southwesterly shear and the dry and
stable atmospheric environment taking their toll on the system.
These hostile environmental factors are not expected to improve,
while the forward path of the cyclone takes it over progressively
cooler waters. Therefore, it is anticipated that persistent deep
convection will not redevelop near the center of the system, and
Blanca is being designated as a remnant low. The low is expected to
gradually spin down and is likely to dissipate within the next few
days. The overnight ASCAT overpasses did not sample the center of
the system, so a blend of the T/CI numbers of 1.0/2.0 from the most
recent satellite intensity estimate from TAFB supports maintaining
the advisory intensity at 25 kt.
Over the past 12 hours Blanca has been moving west-northwestward, or
300/06 kt. A turn to the west is expected later this morning as the
shallow system gets caught up in the flow around a low-level ridge
to the north. This westward motion should continue until the system
dissipates. The latest NHC track forecast is little changed from the
previous one and is near the multi-model consensus.
This is the last NHC advisory on Blanca. For additional information
on the remnant low please see High Seas Forecasts issued by the
National Weather Service, under AWIPS header NFDHSFEPI, WMO header
FZPN02 KWBC, and on the web at ocean.weather.gov/shtml/NFDHSFEPI.php
Tropical Storm Blanca Discussion Number 6
NWS National Hurricane Center Miami FL EP022021
900 PM MDT Mon May 31 2021
The satellite presentation of Blanca has continued to improve this
evening. Bursts of deep convection have recently developed near the
estimated center, which has led to an increase in banding that can
be seen in the latest microwave imagery. Subjective Dvorak
classifications are T3.0 (45 kt) and T3.5 (55 kt) from TAFB and
SAB, respectively. Based on these data and the continued
organization seen in recent satellite imagery, the initial
intensity has been set at 50 kt for this advisory.
Blanca is currently located within a favorable environment for
strengthening that consists of low vertical wind shear, warm sea
surface temperatures, and a moist atmosphere. These conditions
favor additional strengthening during the next 12 hours or so, but
by Tuesday afternoon increasing southwesterly shear is likely to
put an end to Blanca's intensification phase. After that time, an
additional increase in shear and gradually decreasing sea surface
temperatures are expected to cause slow weakening throughout the
remainder of the forecast period. Blanca is now forecast to become
a remnant low by day 5, but it could occur a little sooner than
that. The NHC intensity forecast is in best agreement with the
HCCA and ICON consensus aids.
The initial motion estimate is 300/8 kt, a little slower toward the
west-northwest than before. A deepening mid- to upper-level trough
near the central portion of the Baja peninsula is forecast to
weaken the western extent of the ridge, which is expected to cause
Blanca to slow its forward speed over the next couple of days. As
the tropical storm weakens in 2-3 days, it should turn more westward
when it becomes a vertically shallow system and is steered by the
low-level easterly trade wind flow. Although there is an increase
in the spread of the guidance after 72 hours, the latest NHC track
forecast remains near the middle of the guidance envelope, and it
is very similar to the previous official forecast.
組圖打開中，請稍候......