2. A broad area of low pressure located several hundred miles south of
Acapulco, Mexico, continues to produce disorganized shower and
thunderstorm activity. However, environmental conditions are
expected to be conducive for development of this system during the
next several days, and a tropical depression is likely to form by
the middle of next week while the system moves westward to
west-northwestward at about 10 mph.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 5 days...high...70 percent.
1. Showers and thunderstorms are slowly becoming better organized in
association with a broad area of low pressure located several
hundred miles south-southwest of Acapulco, Mexico. Environmental
conditions are expected to be conducive for additional development
of this disturbance during the next several days, and a tropical
depression is likely to form by the middle of next week while the
system moves westward to west-northwestward at about 10 mph.
* Formation chance through 48 hours...medium...60 percent.
* Formation chance through 5 days...high...80 percent.
1. A low pressure system located more than 500 miles south-southwest
of Acapulco, Mexico, is gradually becoming better defined.
Associated shower and thunderstorm activity continues to show signs
of organization, and environmental conditions are expected to be
conducive for a tropical depression to form at any time during the
next couple of days while the system moves west-northwestward to
westward at about 10 mph.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...90 percent.
1. A well-defined low pressure system located more than 500 miles
south-southwest of Acapulco, Mexico, is moving west-northwestward
at about 10 mph. Showers and thunderstorms have become better
organized this morning, and recent satellite-derived wind data
indicate that winds have increased to just below tropical-storm
strength. Any further improvement in the associated thunderstorm
activity could result in the issuance of advisories on a tropical
depression or a tropical storm later today or tonight.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.
Tropical Depression Two-E Discussion Number 1
NWS National Hurricane Center Miami FL EP022021
400 PM CDT Sun May 30 2021
The area of low pressure that the National Hurricane Center has been
monitoring the past few days well offshore the southwestern coast of
Mexico has continued to become better organized today and, thus, has
now been upgraded to tropical depression status -- the second
depression of the 2021 eastern North Pacific hurricane season. The
initial intensity of 30 kt is based on an ASCAT-A scatterometer pass
at 1442Z that showed several 30-32 kt surface wind vectors located
northwest through north-northeast of the center. Dvorak satellite
intensity estimates at 1800Z were 30 kt from TAFB and 35 kt from
SAB, respectively, a further indication that the cyclone is just
below tropical storm strength.
The initial motion estimate is an uncertain 300/08 kt. Although
recent hi-resolution visible satellite imagery indicates that the
depression has developed a tight, inner-core low-level vortex during
the past few hours, this feature has no continuity. Thus, there is
uncertainty in both the direction and speed of the cyclone at this
time. However, the global and regional models show a general
west-northwestward motion between 8-12 kt around the western
periphery of a deep-layer ridge continuing for the next 3-5 days.
The NHC official track forecast follows that scenario, and lies
between the HCCA corrected consensus model to the left of the
forecast track and the TVCE simple consensus model on the right.
The overall environment appears to be conducive for strengthening
during the next 72 h or so based on SSTs of 29.0-29.5 deg C,
mid-level humidity values of 70-75 percent, and low deep-layer
vertical wind shear of 5-10 kt. The only fly-in-the- ointment is
that both the GFS and ECMWF models show the instability decreasing
to about half its current value by 48 hours. As a result, the
global and regional models, and the SHIPS-LGEM model show the
cyclone peaking at about 45 kt in 36-48 h, followed by gradual
weakening thereafter. In contrast, the SHIPS dynamical-statistical
model intensifies the cyclone to about 55 kt in 48-72 h, then
followed by gradual weakening; the HCCA consensus model is similar
to the SHIPS (DSHP) forecast. Given the aforementioned favorable
environmental parameters, the official intensity forecast is a based
on a blend of the HCCA and Decay-SHIPS intensity models, and lies a
little above the IVCN intensity consensus model.
Tropical Storm Blanca Discussion Number 5
NWS National Hurricane Center Miami FL EP022021
300 PM MDT Mon May 31 2021
Thunderstorms activity has increased markedly since the previous
advisory and convection now wraps almost 75 percent around the
well-defined low-level center. A bullseye ASCAT-B and a partial
ASCAT-A pass at 1717Z and 1602Z, respectively, depicted a few
35-kt surface vectors just northwest of the tight low-level center
along with a small radius of maximum winds (RMW) of about 15 nmi.
Based on the continued increase in the convective organization since
the ASCAT passes, the advisory intensity has been raised to 40 kt,
which is a little below the consensus T3.0/45 kt satellite
intensity classifications from TAFB and SAB, and objective intensity
estimates of 46 kt and 47 kt from UW-CIMSS ADT and SATCON,
respectively.
Blanca is forecast to maintain a general west-northwestward to
northwestward motion along the south side of a deep-layer
subtropical ridge for the next 3 days or so. Thereafter, a gradual
turn to the west-northwest is expected on day 4, followed by a
westward motion on day 5 as the cyclone moves over cooler water and
weakens, thus becoming more vertically shallow and steered by the
low-level easterly trade wind flow. The new official NHC forecast
track is similar to the previous advisory track and lies near the
center of the tightly packed guidance envelope, which is close to
an average of the consensus track models TVCE and HCCA.
Blanca is expected to remain in favorable environmental conditions
of low vertical wind shear less than 10 kt, high oceanic heat
content, and moist low- to mid-level air for the next 24 hours or
so. As a result, steady strengthening is forecast during that
time, with a brief period of rapid intensification a distinct
possibility owing to the cyclone's small RMW. Thereafter, the
combination of increasing westerly wind shear, along with
decreasing SSTs and mid-level humidity, should cause gradual
weakening. The new NHC intensity forecast is a blend of the HWRF,
HCCA, and Decay-SHIPS (DSHP) models, which is slightly above the
previous intensity forecast for the first 24 hours, and then is
very similar to the previous advisory thereafter.
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