熱帯低気圧 西日本付近に接近 台風にはならない予想
2023年8月19日15時、日本の南東海上で熱帯低気圧が発生しました。
この熱帯低気圧は発生当初は小さな渦でしたが、周辺の積乱雲などを巻き込み、21日（月）時点で非常に大きな渦を形成していますが中心付近の風速は大きくなく、今後も風が強まることは少ないと予想されていて、台風に発達する可能性は低いとみられています。
最新の予報では、熱帯低気圧は22日（火）には紀伊半島沖に達し、西日本から東日本の太平洋側に湿った空気が流れ込みやすく、一部の地域で雨となる予報です。
23日（水）には、熱帯低気圧は北西へと進み、西日本に接近するとみられ、熱帯由来の暖かく湿った空気を運び込むため、西日本や東日本の太平洋側を中心に大気の状態が不安定となり、九州から関東甲信では所々で雨や雷雨、激しい雨となる可能性があると予報されています。南東斜面を中心に雨量が多くなる恐れがあります。
24日（木）以降は、太平洋高気圧の縁をまわる暖かく湿った空気が流れ込みやすく、九州から東海を中心に、所々で雨や雷雨がある見通しです。
また、25日（金）頃からは秋雨前線が北日本付近を南下すると予想されています。
熱帯低気圧 気象庁天気図
2023年08月21日09時の実況天気図
気象庁天気図
48時間後 2023年08月23日09時の予想天気図
気象庁天気図
JTWC Tropical Warnings
JTWCは、90Wとして解析
下記衛星写真図中の「SD 05E “DORA”」の意味については、後述参照
JTWC ISSUED at 20230821 0600Z(UTC)
JTWC Current Significant Tropical Weather Advisories Issued at 21/0600Z
ABPW10 PGTW 210600
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE WESTERN AND SOUTH
PACIFIC OCEANS/210600Z-220600ZAUG2023//
RMKS/
1. WESTERN NORTH PACIFIC AREA (180 TO MALAY PENINSULA):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY:
(1) AN AREA OF CONVECTION (INVEST 90W) HAS PERSISTED NEAR 19.2N
155.8E, APPROXIMATELY 611 NM WEST OF WAKE ISLAND.
ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICT A CONSOLIDATING LLCC
WITH ISOLATED CONVECTION TO THE NORTHEAST. A 210000Z MICROWAVE PASS
SHOWS A WEAK LLCC WHICH IS FURTHER SUPPORTED BY A 202333Z ASCAT
METOP-B PARTIAL PASS WHICH SHOWS THE EASTERN PORTION OF A 15KT
CIRCULATION. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS FOR
DEVELOPMENT WITH WARM (29-30C) SEA SURFACE TEMPERATURE, STRONG
POLEWARD OUTFLOW ALOFT AND LOW (10-15KT) VERTICAL WIND SHEAR. GLOBAL
MODELS ARE IN GOOD AGREEMENT THAT THE SYSTEM WILL SLOWLY CONSOLIDATE
OVER THE NEXT 48 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED
AT 10 TO 15 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR
1009 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL
CYCLONE WITHIN THE NEXT 24 HOURS IS LOW.
(2) NO OTHER SUSPECT AREAS.
C. SUBTROPICAL SYSTEM SUMMARY:
(1) THE AREA OF CONVECTION (INVEST 05E) PREVIOUSLY LOCATED NEAR
33.0N 170.3E IS NOW LOCATED NEAR 33.0N 175.1E, APPROXIMATELY 483 NM
NORTHWEST OF MIDWAY. THE SYSTEM IS CURRENTLY CLASSIFIED AS A
SUBTROPICAL DEPRESSION, GENERALLY CHARACTERIZED AS HAVING BOTH
TROPICAL AND MIDLATITUDE CYCLONE FEATURES. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY DEPICT AN ELONGATED CIRCULATION WITH ISOLATED
CONVECTION DISPLACED TO THE SOUTHEAST OF THE LLCC. A 202236Z ASCAT
METOP-B DEPICTS THE STRONGEST WINDS TO THE SOUTHEAST. ENVIRONMENTAL
ANALYSIS REVEALS UNFAVORABLE CONDITIONS FOR TROPICAL TRANSITION WITH
WARM (26-27C) SEA SURFACE TEMPERATURES AND STRONG EQUATORWARD OUTFLOW
ALOFT OFFSET BY LOW (10-15KT) VERTICAL WIND SHEAR AND DRY AIR BEING
ADVECTED INTO THE CIRCULATION. GLOBAL MODELS ARE IN GENERAL AGREEMENT
THAT INVEST 05E WILL TRACK POLEWARD AND EASTWARD WITH A BROAD AND
ASYMMETRIC WIND FIELD. FOR HAZARDS AND WARNINGS, REFERENCE THE FLEET
WEATHER CENTER SAN DIEGO HIGH WINDS AND SEAS PRODUCT OR REFER TO LOCAL
WMO DESIGNATED FORECAST AUTHORITY. MAXIMUM SUSTAINED SURFACE WINDS ARE
ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED
TO BE NEAR 1009 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT
TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS LOW.
(2) NO OTHER SUBTROPICAL SYSTEMS.
2. SOUTH PACIFIC AREA (WEST COAST OF SOUTH AMERICA TO 135 EAST):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY: NONE.
C. SUBTROPICAL SYSTEM SUMMARY: NONE.//
NNNN
参考：International Hurricane / Cyclone / Typhoon Tracking forecast Map
2023年8月21日17時25分時点
下記のマップ中央の黄色い円が90W
90Wの北西にある円は、台風8号ドーラから変わった亜熱帯低気圧（亜熱帯低気圧は、熱帯低気圧と温帯低気圧の両方の特徴を備えたもの）
※JTWC表記 SD 05E “DORA”
SD：Subtropical cyclone
