Forecasters Guide - (IMD), Pune

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Special observations from surface observatories – land stations Need for special observations Except for 03 and 12 UTC charts, the netw ork of coastal observations at the other hours is not sufficient for cyclone w arning w ork. During periods of disturbed weather out at sea, observations from all the coastal and island observatories may be required at synoptic hours other than 03 and 12 UTC also. Therefore, it w ill be necessary to call for special observations on such occasions from observatories at some of the synoptic hours at which they may not take routine observations. Requisitions for special observations can be sent both by ACWCs & CWCs. Sometimes hourly observations are also required. General instructions The follow ing are the general instructions for calling special observations from surface observatories. During depression stage Special observations are to be called from coastal and island stations for the preparation of 1800 UTC chart from the depression stage onw ards (for the issue of Dew Drop bulletin) or even w hen a depression is expected to form. During storm stage When a depression has intensified into a cyclonic storm, additional special observations are to be called at all the other synoptic hours (00, 06, 09, 15 and 21 UTC) also for the preparation of special charts for the issue of Electron, Formula and Gasbag bulletins. When landfall is expected within 24 hrs. How ever, if a cyclonic storm is w ithin striking distance from the coast and the landfall is expected w ithin the next 24 hrs, hourly special observations may be called from a restricted coastal area tow ards w hich the storm is heading, for determining the position of the storm, its intensity as w ell the place and time of landfall etc., from the sequence of hourly changes at these coastal stations. Discretion of Storm Warning Officer It is left to the discretion of the Storm Warning Officer to decide how frequently the special observations are to be called; he should consider each case on its merits. Extra regional observations It is not necessary to restrict the requisitioning of special observation to stations w ithin the region only. Stations outside the region may also be requested directly for special observations. When an observatory station receives request from more than one Cyclone Warning Centre for special observations, the station w ill comply w ith each request independently according to the frequency and duration for which the special observations are called for. METARs Whenever special observations or even the routine observations from extra Indian coastal stations are not available at an ACWC/CWC, the METARs and SPECIEs of the 25
airports of these stations may be obtained through the Aviation Meteorological Offices and utilised for storm w arning purposes. Similarly, on such occasions, the FIR w arnings issued by the foreign Meteorological offices may also be useful. Discontinuance After the system has crossed coast and special observations are no longer needed, the observatories concerned should be informed immediately to discontinue the special observations. Special care should be taken to see that the observations are not received after instructions to discontinue them have been issued. Further messages to stop the observations have to be issued to such observatories w hich still continue to send the special observations. Other Record Record Management The strain of cyclone w ork may lead to errors of judgement and mistakes in execution. These are likely to creep in if care is not taken to systematize the w ork. All warning action is to be reduced to w riting and be subject to a check by an independent person immediately afterwards. Any action taken in connection w ith the storms, over phone should also be recorded in w riting. Records should be in permanent, bound registers w ith numbered pages and should not be kept in loose paper w hich could either be lost or tampered w ith. Action Books Three types of action books, w hich are bound in registers w ith numbered pages are in use in the various CWCs/ACWCs. In general the texts of the inferences / messages/ forecasts/warning should be entered in the appropriate headings and details of the addresses to which these are despatched, the time of issue/despatch and the mode of transmission like, telephone, W/T or messenger are also entered. The text of the messages initially drafted should be copied immediately into the register by the duty assistant and approved by the duty officer. Then these should be trans mitted by the prescribed channels to the concerned addresses and after having been checked by another assistant, the time of despatch as noted in the office copies of the messages should be entered in the register. One page is to be devoted for forecasts pertaining to a single synoptic hour. After action is over the register is to be put up to the Duty Officer w ho w ill check the entries and put up the register to the Director-in-charge of the storm w arning centre. Action book ‘A’ pertains to Regional inferences, forecast, general description of warnings, for Heavy rain, gale, surge etc. Farmer’s bulletin, outlook, A IR bulletins, routine, special and for All India News Cycles. Action book ‘B’ pertains to 2 stage w arnings and Inland w arnings for cyclones, Heavy rain, gales, (Low temperature, Monsoon onset) etc. Albums are maintained in w hich the individual pages give the address of the registred warnees, the area for which warnings are necessary and the phenomena, and the limits (Like Heavy Rainfall amount or w ind speed) of the w arning elements are specified. The Album page numbers pertaining to the w arnings sent should be entered in the action w ork against the addresses. Care should be taken to see that the individual w arnings conform generally to the relevant general w arning for the public broadcast through AIR. Action book ‘C’ pertains to the sea bulletins, Coastal bulletins issued to the Coastal Radio Station, and sea bulletins exchanged w ithin the departmental centres, as w ell as Fisheries Warnings, Port Warnings and other action pertaining to storm w arning w ork like requisitioning of special observations from surface, upper air and Radar stations and from ships out at sea. At Chennai ACWC tw o separate ‘C’; registers are maintained one for Bay and one for Arabian Sea. 26
Page 4 and 5: FORECASTERS’ GUIDE CONTENTS Page
Page 6 and 7: 3.2.4 RELEVANT PORTIONS OF THE RECO
Page 8 and 9: DEFINITIONS Pressure: The pressure
Page 10 and 11: FORECASTING ORGANISATION (NON-AVIAT
Page 12 and 13: S.No. Category/ Meteorological Offi
Page 14 and 15: S.No. Category/ Meteorological Offi
Page 16 and 17: as to reduce the death and damage f
Page 18 and 19: pressure tendency and pressure anom
Page 20 and 21: CHAPTER 3 TERMINOLOGIES IN WEATHER
Page 22 and 23: CHAPTER 5 IMPORTANT PROCEDURES DURI
Page 24 and 25: of Bengal. However, the additional
Page 26 and 27: terrestrial links are disrupted. Th
Page 28 and 29: (3) Police W/T Any action required
Page 30 and 31: Action taken by w arnees The action
Page 34 and 35: Other Registers Though the above th
Page 36 and 37: Coastal Station : Name Surface Wind
Page 38 and 39: Annexure I FORMAT OF CYCLONE WARNIN
Page 40 and 41: CHPATER 7 LOCAL FORECAST A detailed
Page 42 and 43: MAP SHOWING THE 36 METEOROLOGICAL S
Page 44 and 45: 2.2 CHANGES IN SHIPS’ AND UPPER A
Page 46: 2.4 ANALYSIS OF UPPER AIR CHARTS. F
Page 52 and 53: 2.7 W3 CHARTS DDGM (WF) UOI No.W-39
Page 54 and 55: 3. TERMINOLOGY: 3.1 RAI NFAL L 3.1.
Page 56 and 57: 3.1.3 INTRODUCTION OF EXTREM ELY HE
Page 58 and 59: 3.1.5 TERMINOLOGY OF RAINFALL DISTR
Page 60 and 61: 1.5 When a station satisfies both t
Page 62 and 63: Wind-chill equivalent temperature (
Page 65 and 66: 3.2.3 DESCRIBING NORMAL TEMPERATURE
Page 67 and 68: 3.2.5 DESCRIPTION OF 24 HRS TEMPERA
Page 69 and 70: 3.3.2 DESCRIPTION OF PRESSURE GRADI
Page 71 and 72: 3.4. NOMENCLATURE FOR DIFFERENT PAR
Page 73 and 74: 4. WEATHER FORECASTS, BULLETINS AND
Page 75 and 76: 4.2 SECOND FARMER’S WEATHER BULLE
Page 77 and 78: 4.4. ISSUE OF WEEKLY WEATHER MAPS.
Page 79 and 80: 4.6. COMPACTNESS OF WEATHER BULLETI
Page 81 and 82: 2.1 Free supply of the RDWR of the
Page 83 and 84:
5. MONSOON PROCEDURES 5.1 ONSET/ WI
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II Further advance of monsoon over
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Normal for these stations Average n
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5.2.3 SUBDUED MONSOON ACTIVITY FORE
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5.2.5 HIGH TEMPERATURE EPOCHS WHICH
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5.3 CRITERIA FOR DECLARING ONSET OF
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6. PROCEDURES DURING THE CYCLONE PE
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6.2. CRUCIAL OBSERVATIONS RESPONSIB
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6.4 PRE CYCLONE PROCEDURES Forecast
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6.5 WARNINGS FOR STRONG WINDS EXPEC
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Date and Time of Issue …………
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CYCLONE WARNING: 4. Format of Cyclo
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NOTES : a] In the bulletins for gen
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6.7 UNIFORMITY IN MAINTAINING THE I
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6.9 INSTRUCTIONS FOR RMCS / MCS FOR
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public is interested to know about
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4. Wind : For indicating forecast w
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“Mainly clear skies; Maximum temp
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HEAT INDEX °F (°C) RELATIVE HUMID
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Verification of Local Forecast The
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STAGES OF VERIFICATION OF FORECASTS
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2.4 Expression of confidence Foreca
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11.3 Marks allotted to various elem
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1..3.1.2 Height of tops 4 (i) Less
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2.3 Upper air temperatures 3 Same a
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-6 to -8 -3 to -4 Appreciably fall
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RULES OF V ERIFICA TION OF FORECAST
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8.2 LOCAL FORECAST VERIFICATION FOR
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Format for Local Forecast issued at
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8.4 REVISED FORECAST VERIFICATION M
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DETERMINISTIC FORECAST Annexure I (
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VERIFICATION OF SPATIAL DISTRIBUTIO
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Forecasters Guide - (IMD), Pune

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